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Keywords:

  • health-related quality of life;
  • measurement;
  • questionnaires;
  • Type 2 diabetes

Abstract

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Generic Instruments
  6. Diabetes-Specific Instruments
  7. Condition-Specific Battery Measures
  8. Psychological Functioning
  9. Factors Affecting HRQoL
  10. Discussion
  11. Acknowledgments
  12. References

Type 2 diabetes has significant adverse effects on health-related quality of life (HRQoL). A vast array of questionnaires has been used to measure HRQoL in diabetes patients, contributing to the difficulty of selecting instruments for future research. To systematically evaluate these measures, a literature search was undertaken to identify relevant publications. This paper summarizes the generic, diabetes-specific, and psychological measures utilized to evaluate persons with type 2 diabetes, and highlights related findings. Generic instruments demonstrate significant reductions in health status compared with other chronic disease populations and healthy controls. Multiple diabetes-specific measures are available to assess domains affected by the disease, including symptoms, worries, self-care, locus of control, functional ability, social support, and sexual functioning. Psychological measures show that type 2 diabetes is frequently associated with adverse psychological effects, particularly depression. Since much of this research has been cross-sectional in nature, little is known about responsiveness of many of the HRQoL measures to clinical change and treatment effects. It is clear that HRQoL results are influenced by multiple patient and disease factors, particularly age, gender, and the presence and severity of disease complications and comorbid conditions. These factors should be considered in the design and analysis of HRQoL evaluations in type 2 diabetes patients. Selection of instruments for future research will therefore require careful evaluation of study design and objectives, population characteristics, the presence of disease-related factors, and outcomes of interest.


Introduction

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Generic Instruments
  6. Diabetes-Specific Instruments
  7. Condition-Specific Battery Measures
  8. Psychological Functioning
  9. Factors Affecting HRQoL
  10. Discussion
  11. Acknowledgments
  12. References

The adverse effects of diabetes on health-related quality of life (HRQoL) are described in a growing body of literature. The illness, its complications and treatments, and patient attitudes all interact to impair multiple dimensions of HRQoL, including physical, role, social, cognitive, and sexual functioning, emotional well-being, pain, and health perceptions or distress. In patients with older onset diabetes, self-rated health is a significant predictor of mortality when physical health status is controlled [1].

Type 2 diabetes accounts for at least 90% of diabetes cases in developed countries. Care of type 2 diabetes and related complications comprises a significant proportion of health care expenditures in the US and elsewhere and substantial indirect costs result from premature mortality and lost productivity [2]. Formerly considered to be adult-onset diabetes, incidence of type 2 diabetes is increasing in younger populations including adolescents and children [3,4]. Because of the considerable societal burden of type 2 diabetes, its impact on HRQoL is a public health issue of concern to patients, families, employers, health care providers, and payers [3].

A variety of instruments has been used to measure HRQoL in type 2 diabetics including generic and diabetes-specific measures, and assessments of functional status and psychological well-being. Generic HRQoL measures provide valuable information about the health status of patients with diabetes and allow comparisons with other populations and chronic diseases groups. Using these measures, investigators have evaluated the association of HRQoL with multiple factors such as glycemic control, types of treatment, numbers and types of complications and comorbid conditions, and demographic variables. In addition, disease-specific measures have been developed to focus on dimensions unique to diabetes. For example, diabetes-specific concerns include the presence and “bother” of diabetes symptoms, attitudes, worries, self-care, treatment satisfaction, adherence to diabetic regimen, locus of control, and social and family support.

An examination of these measures and related findings is useful when choosing an instrument and designing future research. For this reason, a literature review was initiated to identify and describe the generic, diabetes-specific, and psychological measures used in type 2 diabetes, and to highlight key findings. While the effects of specific diabetes complications on HRQoL have important societal implications, a description of the research on complications is beyond the scope of this review.

Methods

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Generic Instruments
  6. Diabetes-Specific Instruments
  7. Condition-Specific Battery Measures
  8. Psychological Functioning
  9. Factors Affecting HRQoL
  10. Discussion
  11. Acknowledgments
  12. References

A MEDLINE search was undertaken from 1985 through February 2000 to ascertain publications on development of measures and systematic evaluations of HRQoL in individuals with type 2 disease. The initial date was selected because a majority of the literature on HRQoL in diabetes has been published since the middle 1980s. The definition of HRQoL utilized in this paper follows the model presented by Wilson and Cleary [5]. HRQoL domains include physical, role, social, and psychological functioning, general health perceptions, and disease-related symptoms and concerns. In addition, measures of diabetes-specific treatment satisfaction were identified in this review.

The search focused on the following topics: diabet*; NIDDM; noninsulin dependent diabetes; type 2 diabetes; quality of life; health status; assessment; and instrument. The selection of HRQoL articles included all reviews and studies validating questionnaires or reporting data relevant to type 2 diabetes. The author screened abstracts, selected pertinent publications, and reviewed the articles to identify HRQoL instruments, studies, and results. Additional relevant publications, noted through a secondary examination of citations, were obtained and included in this review.

The HRQoL instruments that have been utilized in type 2 diabetes research are highlighted below, along with study findings relating to the effects of the disease on HRQoL. Generic and psychological assessments that have been applied to type 2 diabetes are briefly described in Tables 1 and 3, respectively. Table 2 describes the diabetes-specific measures with supporting psychometric evaluations. Tables 1-3 are grouped together at the end of the paper.

Table 1.  Generic quality of life questionnaires used in type 2 diabetic populations
MeasureDescription
Short Form 20 (SF-20)6 subscales: physical, role, and social functioning; mental health; pain; health perceptions; summed items within scales; transformed to 0-100 scale where 100 is best
Short Form 36 (SF-36)36 items, 8 scales: physical functioning, role functioning (physical or emotional), bodily pain, general health, vitality, social functioning, mental health; scale scores transformed to 0–100 scales where 100 is best; physical and mental health summary scores can also be calculated
Sickness Impact Profile (SIP)136 statements: physical and psychosocial dimensions and independent categories; scores for overall SIP, 12 categories, and 2 dimensions
Dartmouth COOP/ WONCA Chart6 domains assessed by single items on a 5-point scale: physical activities, feelings, daily activities, social activities, change in health, and overall health; a pictograph represents the options
Nottingham Health Profile (NHP)38 items, 6 domains: energy, sleep, pain, physical mobility, emotional reactions, social isolation; scores are weighted and transformed to 0–100 scale; high score is greater severity
Quality of Well-Being Scale (QWB)3 functional scales (mobility, physical activity, social activity), 36 symptom/problem complexes (later reduced to 25) [98]; QWB index adjusted by preference weights obtained from random samples of general population
EuroQol (EQ5D)5 dimensions with 3 levels of responses: mobility, self-care, usual activity, pain/discomfort, and anxiety/depression; single index, 5 domain scores; used in valuation of health states
Well-Being Questionnaire (WBQ)18 items measuring psychological well-being are scored on a 4-point Likert Scale for an overall general well-being scale and 3 subscales: depression, anxiety, and positive well-being
World Health Organization Quality of Life Questionnaire (WHOQOL)100 items scored on a 5-point Likert scale; overall quality of life and 6 domains: physical health; psychological state; level of independence; social relationships; environment; spirituality, religion and personal beliefs; higher results indicate better HRQoL [99]
Table 3.  Psychological measures used in type 2 diabetes populations
MeasureDescription
Affect Balance Scale (ABS)5 positive and 5 negative items; positive, negative and aggregate balance scores
Center for Epidemiologic Studies-Depression (CES-D) Scale20 items that measure depressive symptoms
Zung Self-Rating Depression Scale (ZSDS)20 items yield a score ranging from 20 to 80; a ZSDS index calculated by multiplying score value by 1.25
Short Zung Self-Rating Depressive Scale10 items on a 4-point Likert scale yield an overall score
Symptom Check-List 90-Revised (SCL-90-R)9 subscales: somatization, obsessive-compulsive symptoms, interpersonal sensitivity, depression, anxiety, hostility, phobic anxiety, paranoid ideation, psychoticism, and a global symptom index that measures the severity of psychological symptoms
Hospital Anxiety and Depression Scale (HADS)Identifies states of depression and anxiety in hospital outpatients; subscales also measure severity of the emotional state [100]
Beck Depression Inventory (BDI)Measures existence and severity of depression; 84 statements; 21 categories; somatic and affective subscales; items rated on 4-point severity scale; total score ranges from 0 to 63; high score indicates worse depression [101,102]
Profile of Mood State (POMS)Describes extent of 58 feelings on a 5-point scale; scores for 6 mood states: tension/anxiety, depression/dejection, anger/hostility, vigor/activity, fatigue/inertia, confusion/bewilderment, and total mood-disturbance
Table 2.  Self-administered diabetes-specific scales used in type 2 diabetes
InstrumentScalesStudiesPsychometric Findings (Psychometric evaluation performed for total study population unless otherwise specified)
Diabetes Quality of Life (DQOL)46 items, 4 scales: satisfaction, impact, diabetes-related worry, social/vocational worry; 5-point Likert scale; higher score represents lower HRQoLDeveloped for the Diabetes Control and Complications Trial (DCCT) [42,43,49,54]Oriented for type 1 diabetes, but also used in type 2; internal consistency, test-retest reliability and convergent validity demonstrated in type 1 [43]
DQOLThe DQOL transformed to 100-point scale with 100 representing highest HRQoL; not all items relevant for type 2 patientsCross-sectional study of 240 outpatients geqslant R: gt-or-equal, slanted18 years of age; 129 were type 2 of whom 53% used insulin [42]Psychometric evaluation of DQOL and SF-36 confirmed reliability of the measures and modest overlap in areas of functioning; DQOL not confounded by education, sex, or duration of diabetes but was affected by marital status
DQOL Cross-sectional survey of Chinese immigrants with type 2 diabetes [47]Pilot study to test instruments translated into Chinese; internal consistency reliability satisfactory
DQOL Cross-sectional survey of 70 type 2 elderly diabetes patients in Toronto [48]Internal consistency and test-retest reliability satisfactory; a trend toward increasing scores with more complications suggests divergent validity
Diabetes Quality of Life Clinical Trial Questionnaire (DQLCTQ)Revised version contains 57 items, 8 generic and disease-specific domains: physical function, energy/fatigue, health distress, mental health, satisfaction, treatment satisfaction, treatment flexibility, and frequency of symptoms. Scores converted to a 100-point scale with higher values indicating better HRQoLPilot study and 2 randomized cross-over multinational trials of 6 months duration; 468 type 1 patients and 474 type 2 patients treated with insulin [44,45]Internal consistency, reliability and test-retest reproducibility acceptable for most domains; social stigma and social and diabetes worry scales eliminated because of low reliability; final 8 domains discriminated between the sexes, diabetes type, tight and poor metabolic control, and good and poor self-perceived control; responsiveness to clinical change in metabolic control shown for treatment satisfaction, health/distress, mental health, and satisfaction
Diabetes-3939 items, 5 scales: energy and mobility, diabetes control, anxiety and worry, social burden, and sexual functioning; scored on a VAS (visual analog scale) from 1 to 7; 0-100 score with high score indicating maximum impact2 cross-sectional development and validation studies in probable types 1 and 2 patients [55]Internal consistency reliability correlations above 0.70; construct validity evaluated relative to SF-36 with strong correlations except for diabetes control and sexual function scales
ATT39 Scale39 Likert-scale items measuring emotional adjustment in diabetics; high scores indicate a negative attitude to diabetesValidation study in Sydney included 166 type 2 patients [57]Internal consistency; test-retest reliability at 2 weeks, 3 and 6 months demonstrated
Problem Areas in Diabetes Survey (PAID)20 items measure psychosocial adjustment to diabetes on a 6-point Likert scale; sums to a total scale scoreCross-sectional survey of 451 types 1 and 2 female patients requiring insulin (82% type 1) [58]Psychometric study included other measures, e.g., Brief Symptom Inventory and Hypoglycemia Fear Survey; internal consistency satisfactory for PAID
Diabetes Care Profile (DCP)234 items, 14 scales: control problems; social and personal factors; positive and negative attitude; self-care ability, importance of care; self-care and diet adherence; medical, exercise, and monitoring barriers; long-term care benefit; understanding management practice; support attitudeCross-sectional studies in two samples: 440 diabetics from 8 communities (89% type 2) and 428 medical center patients (67% type 2); 34% of type 2 diabetics used insulin [61]Examined reliability, construct and concurrent validity; reliability coefficients ranged from 0.60 to 0.95; lower scores on the CESD Scale correlated with higher self-care adherence and fewer monitoring problems; other correlations support validity
DCP16 scales were assessed: 14 scales as above plus support and support needsCross-sectional survey of 746 patients, 98% type 2; 511 were African American (53% using insulin) [62]Reliability of DCP satisfactory in both African American and Caucasian type 2 patients, except the support attitude scale had a reliability coefficient <0.70
DCP8 DCP scales were evaluated: control problems, social and personal factors, positive and negative attitude, self-care ability, exercise barriers, long-term care benefits, support attitudesCross-sectional survey of 255 type 2 (36% on insulin) [17]Internal consistency reliability and correlations with SF-36 demonstrated for the 8 scales
Diabetes Health Profile (DHP)43 items, 3 dimensions: barriers to activity, psychological distress, disinhibited eating; 4-point Likert scaleCross-sectional study of 2239 insulin requiring and insulin dependent patients in the UK [96]Internal consistency satisfactory; construct-convergent validity supported by correlations with SF-36 and HADS
DHP Cross-sectional validation study of 99 type 2 patients referred for insulin therapy in The Netherlands [12]DHP adapted to Dutch using forward and backward translations; internal consistency satisfactory; most correlations with SF-36 as expected
Diabetes Impact Measurement Scales (DIMS)Scores for total scale and 4 subscales: diabetes-specific symptoms, nonspecific symptoms, diabetes-related morale, social-role fulfillment, well-being; high scores are more positivePsychometric study of 130 types 1 and 2 patients (77% on insulin, 59% type 2) [63]One major factor identified; internal consistency and test-retest reliability satisfactory
Diabetes Health Status Questionnaire (DHS)20 diabetes-related symptoms and 6 items rating current health and energy on a 5-point Likert scaleLongitudinal study of lifestyle modification for weight control in 66 type 2 patients [64]Internal consistency reliability satisfactory
Perceived Control scales7 subscales and 3 composite scores: personal control, medical control, and situational controlCross-sectional studies of 286 insulin-requiring patients [35] and 187 patients treated with oral agents [38]Internal consistency satisfactory for composite scales in patients treated with oral agents
Diabetes Treatment Satisfaction Questionnaire (DTSQ)6 items about various aspects of treatment satisfaction rated on a 7-point scale, plus 2 individual items concerning hypo- and hyperglycemiaCross-sectional study of diabetics treated with oral agents [37]181 patients completed the DTSQ; reliability coefficients satisfactory; item-total correlations ranged from 0.53 to 0.62
DTSQ A postal survey of 734 diabetics geqslant R: gt-or-equal, slanted60 years (17% on diet alone, 55% on orals, 28% on insulin) [97]Treatment satisfaction positively associated with oral therapy and correlated with the general well-being score of the WBQ
DTSQ Randomized cross-over study of 105 diabetes patients (45 type 2) [68]Compared standard and computerized Dutch versions of the DTSQ and WBQ; internal consistency and test-retest reliability satisfactory for both measures
DTSQ Cross-sectional study of 423 patients (153 on insulin; 270 diet and/or orals) [67]Psychometric validation of Swedish versions of the DTSQ and the WBQ; internal reliability satisfactory
The Diabetes Activities Questionnaire (TDAQ)13 items scored on a VAS 100 mm in length for total scale and 2 subscales: treatment and lifestyle/monitoringDevelopment and cross-sectional pilot testing in 153 individuals with type 1 or 2 diabetes in Ontario, Canada (53% on oral agents) [69]Factor analysis performed; test-retest reliability suggested stability of the questionnaire and satisfactory internal consistency
Diabetes Fear of Injecting and Self-testing Questionnaire (D-FISQ)30-items, 2 scales: fear of self-injecting (FSI) and fear of self-testing (FST)Cross-sectional study of 266 insulin-treated adult diabetics (types 1 and 2) [70]Internal consistency satisfactory; preliminary evidence of construct and discriminative validity; minimal subscale scores found for 62% (FSI) and 57% (FST) of the population
DSC-Type 28 scales/6 dimensions measure frequency and discomfort of 34 symptoms on 4-point Likert Scale; frequency and weighted scores for each dimension and total symptom scores are calculated [73]DSC-Type 2 used in 3 studies in Netherlands: cross-sectional and 2-year cohort studies, and randomized trial with 1-year follow-upCorrelations with Dutch POMS, Affect Balance Scale, questions of well-being and treatment satisfaction, Netherlands Personality Questionnaire, and HbA1c. Reliability not reported

Generic Instruments (Table 1)

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Generic Instruments
  6. Diabetes-Specific Instruments
  7. Condition-Specific Battery Measures
  8. Psychological Functioning
  9. Factors Affecting HRQoL
  10. Discussion
  11. Acknowledgments
  12. References

The generic HRQoL instruments used most frequently to evaluate type 2 diabetes are those derived from the Medical Outcomes Study (MOS), particularly the Short Form-36 (SF-36) and Short Form-20 (SF-20). Much of this research has been cross-sectional in nature. MOS investigators compared functional status and well being across a number of chronic conditions [6]. Persons with diabetes had among the lowest scores on physical, role, and social functioning and health perceptions, but not on mental health or bodily pain. In a comparison with scores from epilepsy and multiple sclerosis patients, MOS diabetics fared significantly better on the SF-36 mental health scales, but worse than the epilepsy group on health perceptions [7]. The MOS diabetic patients also scored worse than epilepsy surgery patients did on emotional well being [8]. Other cross-sectional studies utilizing the MOS short forms demonstrated poor physical functioning and health perceptions in type 2 diabetes [9] and the adverse effects of complications and comorbid conditions [9–12].

The SF-36 has been utilized in longitudinal studies of glycemic control with various results [13]. An intensive treatment study in the Netherlands demonstrated that all SF-36 scales except physical functioning and general health perceptions significantly improved after one year [14]. In this study, glycemic control was maximized on oral therapy and patients were switched to insulin if necessary. The insulin-treated group had lower scores on social functioning and pain than the noninsulin-treated patients. A 6-month study of diabetic patients (90% type 2) using a day care educational program showed significant improvements in the SF-36, independent of glycemic control [15]. Veteran's Administration outpatients were followed for one year to evaluate whether a nurse-coordinated intervention could improve glycemic control [16]. Investigators found no relationship between SF-36 scores and glycosylated hemoglobin (HbA1c) after controlling for five covariates. Similarly, the SF-36 did not predict glycemic control in type 2 diabetics evaluated as part of a larger cross-sectional study of Michigan communities [17]. In Pima Indians, glycemic control was significantly associated only with the health change scale of the SF-36 [18]. However, a 6-month outcomes monitoring program of diabetic outpatients found differences in physical and social functioning by level of metabolic control with the highest scores relating to moderate control [19]. When doctors rated the SF-36 on behalf of their patients, their scores for general health perceptions, mental health, energy, role functioning (emotional), and pain were better than those reported by their patients [19].

Several HRQoL studies in diabetic patients utilized the SWED-QUAL, a 67-item adaptation of the SF-36 [20–24]. A cross-sectional study found that diabetic patients had lower scores than matched controls for all scales except social health [22]. In an investigation of diabetic patients (a majority treated with oral medications or diet) over a 3-year period, the only deterioration was in the physical functioning scale [21]. Vascular and nonvascular comorbidities were the most significant predicting factors for SWED-QUAL outcomes during the 3 years [23].

HRQoL in type 2 diabetes has been assessed by a number of other generic instruments, listed in Table 1, including the Sickness Impact Profile (SIP), Nottingham Health Profile (NHP), EuroQol (EQ5D), Quality of Well-Being Scale (QWB), Dartmouth COOP/WONCA chart, Well-Being Questionnaire (WBQ), and the World Health Organization Quality of Life Questionnaire (WHOQOL).

Like many of the SF-36 studies, the SIP was unaffected by metabolic control in a Dutch cross-sectional study [25]. Both the SIP and the NHP showed impairments in diabetic patients compared with nondiabetic controls [25]. A cross-sectional study of social support and depression found that depressive symptoms correlated with functional impairment as measured by the SIP, and social support moderated depression in patients who reported the most functional disabilities [26]. Two cross-sectional studies utilizing the NHP found that neuropathy negatively impacted HRQoL [27,28]. Other SIP and NHP evaluations indicated that circulatory problems, angina, and other comorbid conditions were associated with reduced functioning [27–29]. In a Finnish cross-sectional study, patients being treated with diet alone had significantly better NHP scores than those on orals or combination therapy, even after results were standardized for age and gender. These differences could be at least partly due to the shorter duration of diabetes in the diet group since duration was found to be a significant predictor for HRQoL problems [29]. In a longitudinal study, the NHP showed significant improvements for up to two years after coronary artery bypass grafting in type 2 diabetic patients [30].

The UK Prospective Diabetes Study (UK PDS) of over 2000 type 2 patients and 122 controls found no significant differences in EQ5D scores between groups receiving intensive vs. conventional glucose control. However, macrovascular complications in the last year were associated with worse general health and more problems with mobility and usual activities. The macrovascular complications included nonfatal myocardial infarction, angina, heart failure, and stroke [31].

Both the QWB and HbA1c showed improvements during an 18-month trial in patients assigned to combined diet and exercise compared with a control group who received education only [32].

In a Dutch study utilizing the COOP chart, type 2 diabetic patients scored significantly worse than matched controls on physical fitness and overall health [25].

The WBQ is one of several scales developed by Bradley and colleagues to assess the effects of diabetes [33–40]. Development of this scale was based on the Health Belief Model [35,40]. Although no correlation was found between WBQ and HbA1c levels, depression and anxiety were associated with patient ratings of recent diabetic control [37]. Women had significantly higher depression and anxiety and lower general well-being scores than men and their anxiety scores correlated with more overweight [37].

Croatian investigators used the WHOQOL in a 2-month study of patients switched from oral to insulin therapy compared with patients remaining on orals [41]. In this small sample, patients switched to insulin had worse scores for overall HRQoL and independence level than those remaining on orals, but switched patients improved in psychological state.

Diabetes-Specific Instruments (Table 2)

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Generic Instruments
  6. Diabetes-Specific Instruments
  7. Condition-Specific Battery Measures
  8. Psychological Functioning
  9. Factors Affecting HRQoL
  10. Discussion
  11. Acknowledgments
  12. References

A large number of diabetes-specific instruments have been developed. Some of these measures have been used in both type 1 and type 2 diabetes. Two diabetes-specific instruments were created for application in clinical trials. The Diabetes Quality of Life (DQOL) measure was devised for the Diabetes Control and Complications Trial (DCCT) [42,43] and the Diabetes Quality of Life Clinical Trial Questionnaire (DQLCTQ) was incorporated into treatment trials with insulin lispro [44,45].

Although the DQOL was developed for evaluation of type 1 diabetics, it has also been used to assess type 2 patients [42,46–48]. In addition to four scales encompassing satisfaction, impact, diabetes-related worry, and social/vocational worry, the DQOL also includes 16 items that assess schooling, experience, and family relationships of adolescent populations [49]. The instrument has been adapted to other languages [47,48,50,51] and use in youths [52,53]. Results of the DCCT appear to demonstrate that patients undergoing intensive treatment for type 1 diabetes do not experience HRQoL decrements in spite of increased frequency of hypoglycemia and more demands relating to diabetes care [54]. However, it is possible that the DQOL and other instruments used in the trial are not sufficiently sensitive to detect differences relating to improved glycemic control and delayed onset of disease complications.

The DQLCTQ was validated and refined in multinational clinical trials of insulin treatment for types 1 and 2 diabetics [44,45]. Items and scales were drawn from the MOS and DQOL, with the addition of newly constructed domains. Two generic scales (energy/fatigue and health distress) and 2 diabetes-specific domains (treatment flexibility and treatment satisfaction) were used as primary outcomes in multinational trials of insulin treatment. These crossover trials, conducted in the US, Canada, France, and Germany, evaluated three months of treatment with insulin lispro compared with regular human insulin in types 1 and 2 diabetics. Both treatment satisfaction and treatment flexibility were significantly improved for type 1 patients treated with the insulin lispro, but no significant HRQoL improvements were noted for type 2 patients [44].

Most of the other diabetes-specific measures have been examined in cross-sectional studies and show at least preliminary internal consistency and reliability. Some of the measures have been evaluated for test-retest reliability or stability. Because very few longitudinal studies have been conducted with the instruments, responsiveness to clinically meaningful change is largely unknown.

A cross-sectional validation study for the Diabetes-39 provided initial evidence of the instrument's reliability and construct validity in probable types 1 and 2 diabetes patients [55]. The instrument has been shown to discriminate between perceived levels of diabetes severity and types of therapy (patients on combination therapy had worse scores than the other therapy groups). The measure has also been translated into multiple languages [56].

Several instruments were developed to assess diabetes adjustment and self-care. The ATT39, designed in Australia [57], and the Problem Areas in Diabetes Survey (PAID), tested in Boston females requiring insulin [58], measure emotional or psychosocial adjustment to diabetes. Relative stability was demonstrated with the ATT39 over a 6-month period. The PAID was associated with HbA1c even after adjustments for age, diabetes duration, general emotional distress, and adherence to self-care behaviors [58]. The PAID score was also related to psychosocial distress, disordered eating, fear of hypoglycemia, and complications. No differences in the scores were found between types 1 and 2 diabetes.

The Diabetes Care Profile (DCP) measures psychosocial and educational needs of individuals with diabetes, and includes scales for self-care and support attitudes. The instrument was originally developed as the Diabetes Educational Profile [59,60]. While the instrument contains 14 scales [61], two more were added for a study conducted in both African American and Caucasian diabetics [62]. Eight of the scales were compared with the SF-36 in another community-based cross-sectional study [17]. The DCP was found to have predictive validity with regard to glycemic control, while the SF-36 did not. The DCP scores differed by diabetes type and treatment [61], and more severe disease was associated with greater difficulty controlling diabetes. Insulin-treated patients reported greater disease impact on their social and personal lives, and more exercise barriers and support needs than patients not using insulin [61,62]. The social and personal factor and positive attitude subscales correlated with reports of at least one complication in patients using insulin [17].

The Diabetes Health Profile (DHP) evaluates the psychosocial profile of insulin-requiring patients, including barriers to activity, psychological distress, and disinhibited eating. It has been adapted to Dutch and tested in Dutch populations referred for insulin therapy [12,14]. The Dutch version was insensitive to number of complications [12]. Younger age, hypertension, and retinopathy negatively influenced disinhibited eating. A hyperglycemic complaint of fatigue had a significant negative impact on psychological distress and barriers to activity [12].

The Diabetes Impact Measurement Scale (DIMS) assesses diabetes symptoms, morale, social-role fulfillment, and well-being for both types 1 and 2 diabetics [63]. A cross-sectional study found high correlations with global ratings of clinical status by patients and clinicians, but low correlations with clinical data.

The Diabetes Health Status Questionnaire (DHS) was developed for a longitudinal study of lifestyle modification to control weight in type 2 patients [64]. The score was not significantly improved after 4 months of treatment with life-style modification.

The perceived control scales [35,38] and Diabetes Treatment Satisfaction Questionnaire (DTSQ) [37,65] are among the scales developed by Bradley, Lewis and colleagues. The perceived control scales measure personal, medical, and situational control. The scales were tested in both insulin-requiring diabetics and patients using oral agents. Cross-sectional studies found that diabetic patients were more likely to attribute responsibility for their diabetes management to personal rather than medical or situational control [35,38]. Furthermore, patients scoring higher on the personal control scale had better glycemic control, general well-being, treatment satisfaction, and lower weight.

The DTSQ was adapted and extended from a measure designed for type 1 patients and was found to correlate strongly with the WBQ [37]. Treatment satisfaction was associated with less overweight in men, and lower HbA1c levels and better ratings of recent diabetic control in both sexes [37]. Both the DTSQ and the WBQ have been adapted for use in a number of countries. The JEVIN-trial conducted in Germany applied these questionnaires in a comparison of intensive vs. conventional insulin therapy in type 2 diabetics. No differences in either measure were found between the two treatment groups [66]. In a Swedish psychometric study of the DTSQ, insulin-treated women had lower treatment satisfaction scores than diet/tablet-treated women [67]. A Dutch study found no significant differences between the computerized and standard versions of the DTSQ scale [68].

The Diabetes Activities Questionnaire (TDAQ) measures adherence to the diabetes regimen. This instrument was developed and tested in types 1 and 2 diabetic patients treated with either insulin or oral agents in Ontario, Canada [69]. Preliminary evidence of reliability was demonstrated for the total scale and two subscales, treatment and lifestyle monitoring.

Two measures are included in Table 2 although they do not measure overall HRQoL. Initial validation of the Diabetes Fear of Injecting and Self-testing Questionnaire (D-FISQ) was conducted in adult insulin-treated diabetic patients [70]. The authors suggest its usefulness for both clinical practice and research. The Type 2 Diabetes Symptom Checklist (DSC-Type 2) has been used in several Dutch HRQoL studies [71,72] to examine the relationship of symptoms with glycemic control and measures of neuroticism, well-being, and mood [73]. A cross-sectional study found that higher HbA1c levels correlated with worse DSC-Type 2 scores for all domains except hypoglycemic, cardiovascular, and ophthalmological [71]. A 1-year follow-up study was conducted with patients randomized to two different target levels of glycemic control. Participants completed the Netherlands Personality Questionnaire, the DSC-Type 2, a shortened version of the Profile of Mood States, and the Affect Balance Scale [73]. Patients who scored high on the neuroticism scale tended to report significantly more symptoms. A decrease of 1% or more in HbA1c had an unfavorable effect on neuropathic sensibility symptoms. The other symptom scales were not significantly affected, except for improvements in the hyperglycemic and cardiovascular scales in persons 70 years of age or greater. All symptom scores except hyperglycemic and ophthalmological tended to be worse with initiation of insulin treatment. A prospective 2-year cohort study examined the effect of insulin treatment in 39 patients who had been treated with diet and/or oral hypoglycemic agents [72]. The initiation of insulin therapy was significantly associated with improved glycemic control and weight gain. DSC-Type 2 scores were not significantly influenced by the initiation of insulin treatment, but high insulin doses were associated with worse overall symptom and hypoglycemic scale scores.

Condition-Specific Battery Measures

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Generic Instruments
  6. Diabetes-Specific Instruments
  7. Condition-Specific Battery Measures
  8. Psychological Functioning
  9. Factors Affecting HRQoL
  10. Discussion
  11. Acknowledgments
  12. References

A number of studies utilized batteries of instruments or constructed scales to evaluate HRQoL in diabetic patients. Using constructed measures, a 24-week treatment study found no differences between treatments when evaluating depression, anxiety, energy, positive well-being, and treatment satisfaction in type 2 patients treated with insulin vs. oral agents [74].

One battery, developed for measuring HRQoL in hypertensive patients with diabetes, included items from the Mental Health Index as well as constructed scales for general health perceptions and sleep disturbance, disease-specific health perceptions, sexual dysfunction, general health status, side-effects, and symptoms [75]. A pilot study demonstrated preliminary evidence for internal consistency and test-retest reliability of the scales. The measures discriminated among groups of normal volunteers, diabetic patients, and hypertensive patients [75]. The hypertensive patients reported the highest degrees of life interference due to symptoms such as “fatigue, tiredness, feeling unwell or other physical ailments.”

These authors also examined HRQoL changes in a 12-week placebo-controlled trial of glipizide gastrointestinal therapeutic system (GITS) using five visual analogue scales that measured perceived health, mental health, cognitive function, symptom distress, and an overall HRQoL rating [76]. Treatment differences favoring the GITS group were found in all of the domains except the mental health scale, but subscales for emotional health and depression were significantly improved in the GITS group. Favorable HRQoL outcomes were associated with reduced distress from hyperglycemia symptoms. Symptoms of hypoglycemia did not differ between the treatment groups. Calibration showed that increases in HbA1c levels of 1% or greater were associated with substantial decrements in HRQoL while HbA1c reductions were related to smaller positive changes in HRQoL. At the end of this trial, a subgroup of patients was asked to rate 10 health-state descriptions on a thermometer scale ranging from 0 (death) to 100 (full health). The mean rating of their current health of 83 ± 8% was inversely correlated with baseline fasting glucose levels [77]. Results of this survey suggest that glycemic control may influence HRQoL [78]. The authors conclude that some generic HRQoL measures may be too insensitive to identify changes at these levels.

Psychological Functioning (Table 3)

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Generic Instruments
  6. Diabetes-Specific Instruments
  7. Condition-Specific Battery Measures
  8. Psychological Functioning
  9. Factors Affecting HRQoL
  10. Discussion
  11. Acknowledgments
  12. References

Multiple psychological measures have been utilized in diabetes research, including the Center for Epidemiologic Studies-Depression (CES-D) Scale, Zung Self-Rating Depressions Scale (ZSDS), Short Zung Self-Rating Depressive Scale, Symptom Check-List 90-Revised (SCL-90-R), Profile of Mood States (POMS), Hospital Anxiety and Depression Scale (HADS), and Beck Depression Inventory (BDI).

The CESD and the Zung measures indicated more depression in diabetic subjects compared with nondiabetic controls in French and Finnish studies [79,80]. In one of the cross-sectional Finnish studies, depression as measured by the ZSDS was associated with HbA1c of greater than 9% and combined oral and insulin treatment. Another Finnish study of diabetics with 10 years duration of the disease found no difference in ZSDS scores when results were compared with nondiabetic controls [81].

Use of the SCL-90-R in outpatients with types 1 and 2 diabetes suggests that both recent and past psychiatric disorders influence HRQoL, and the negative effects increase with severity of psychiatric symptoms [82]. Jacobson et al. found no significant interactions between diabetes type, numbers of complications, or psychiatric status. The authors concluded that psychiatric interventions for conditions such as depression could improve the HRQoL of diabetic patients.

Two studies utilizing the POMS were conducted in patients participating in the UK PDS [31,83]. No significant differences in scores were identified by type of therapy (intensive vs. conventional glucose control). However, more total mood disturbance and tension were found in patients who reported a microvascular complication in the past year and in insulin-treated patients with at least two hypoglycemic episodes during that time.

Dutch studies of type 2 diabetic patients were conducted with a shortened version of the POMS. These included a cross-sectional evaluation of glycemic control [71], a 1-year randomized study of two glycemic control target levels [73], and a 2-year cohort study of well-being and symptoms in relation to insulin therapy [72]. In the 1-year study, a decrease of 1% or more in HbA1c was associated with favorable changes on the displeasure scale (depression, anger, and tension) and a decline in the tension score in women. The cross-sectional study found that worse fatigue scores were associated with higher HbA1c levels. The displeasure score was 29% higher (worse) in patients who started insulin therapy than those who did not.

The HADS was administered to a group of London outpatients to evaluate the relationship of anxiety and depression with HRQoL [84]. HRQoL was measured by an enhanced MOS-36 previously tested in an UK sample of persons with HIV [85]. Patients with depression reported lower scores on all the scales except pain. Anxiety was associated with lower scores except for the physical, social, and role functioning scales.

The BDI effectively discriminated depressed from nondepressed diabetic subjects in a cross-sectional study [86], and was used to show a positive correlation between depressive symptoms and functional impairment as measured by the SIP [26]. Previously diagnosed diabetics had higher age-adjusted scores on the total BDI and affective and somatic subscales than either newly diagnosed diabetics or normal adults [87]. Number of chronic conditions and age were independent predictors of depressive symptoms.

Factors Affecting HRQoL

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Generic Instruments
  6. Diabetes-Specific Instruments
  7. Condition-Specific Battery Measures
  8. Psychological Functioning
  9. Factors Affecting HRQoL
  10. Discussion
  11. Acknowledgments
  12. References

The impact of diabetes on HRQoL is influenced by factors such as age, gender, and presence or severity of complications and comorbid conditions [12,18]. Physical functioning and health perceptions appear to be particularly sensitive to these factors [9–11,17].

Advancing age of people with diabetes has been associated with reduced physical functioning, better mental health, increased resignation to chronic illness, and less tolerance for ambiguities of the disease [9,10,29,56,57]. A population-based study found that age and number of other chronic conditions were independent predictors of depressive symptoms, particularly for previously diagnosed patients; newly diagnosed patients did not differ from normal individuals [87].

Gender also influences how patients report HRQoL. Men with diabetes tend to report better HRQoL than women, consistent with general population studies [56]. One group of investigators found that women had more depression and anxiety and lower scores for general well-being than men and their anxiety scores correlated with more overweight [37]. Others documented higher treatment satisfaction and less disease impact or burden in men [56].

The presence of complications or comorbid conditions is perhaps the most significant influence on HRQoL of diabetic patients. Both the number and severity of complications consistently impair HRQoL [9,10,12,17,27,31,35,40,58]. Duration of disease has shown a variable effect, and may not be as important a factor as the number and severity of complications. In two Finnish studies, duration was associated with reduced HRQoL, particularly physical functioning [11,29]. Conversely, a Swedish study found no association between disease duration and WBQ or DTSQ scores [67]. Similarly, disease duration did not affect scores of the Diabetes-39 instrument in cross-sectional validation studies [55].

While research indicates that depression and other psychiatric symptoms are increased in outpatients with diabetes compared with nondiabetic controls [79,80,87–89], one group of authors suggests that biases and methodological problems encountered in prevalence studies may interfere with the strength of these findings [90]. In addition, it is uncertain whether complications or comorbid conditions increase depressive symptoms in diabetic patients. Some research suggests that depression in individuals with diabetes is independent of complications [82]. Most other studies show that depressive symptoms are worse in the presence of these conditions [87,89,91,92], particularly neuropathy [81,93].

The effect of treatment regimens on HRQoL is uncertain. There is some evidence that HRQoL diminishes as treatment moves from diet and exercise to oral agents to combination therapy or insulin alone [56]. However, this progression may also reflect increased severity of the disease, advancing age, increased obesity, and more complications and comorbid conditions. Insulin treatment has been associated with reduced satisfaction with diabetes and greater impact of the disease on social and personal lives [42,61]. A Netherlands study found that patients switched to insulin had lower scores on social function and pain [14]. Treatment with a combination of insulin and oral agents has been associated with impaired mental health [11].

Discussion

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Generic Instruments
  6. Diabetes-Specific Instruments
  7. Condition-Specific Battery Measures
  8. Psychological Functioning
  9. Factors Affecting HRQoL
  10. Discussion
  11. Acknowledgments
  12. References

The HRQoL consequences of type 2 diabetes are considerable. Research indicates decrements in virtually all aspects of HRQoL due to the disease or its complications. Generic instruments demonstrate significant reductions in health status compared with other chronic disease populations and healthy controls. Studies with diabetes-specific instruments report negative effects on multiple domains including symptoms, worries, self-care, locus of control, functional ability, social support, and treatment satisfaction.

It is important to consider population and disease characteristics in the design and analysis of HRQoL studies since they may be significant covariates. The selection of HRQoL instruments is also influenced by these factors, along with study objectives, outcomes of interest, and relevant data on reliability, validity, and responsiveness.

A generic HRQoL measure may be the optimal choice of instrument when the primary goal is discrimination between types of chronic disease, patient subgroups, or levels of disease severity. While the SF-36 has been the most frequently used generic instrument to study type 2 diabetes, several other measures have been utilized with some success. Applications of generic instruments in longitudinal studies have resulted in variable relationships between HRQoL and glycemic control. It is possible that these measures lack sensitivity to changes in metabolic status.

Disease-specific instruments that include concepts closely aligned with concerns of diabetes patients may be more likely than generic measures to show responsiveness in treatment trials. An association between HRQoL and glycemic control has been documented with several of the instruments. All eight of the DQLCTQ domains discriminated between tight and poor metabolic control, and good and poor self-perceived control. Responsiveness to clinical change in metabolic control was shown for four domains [45]. PAID was associated with glycemic control after adjustment for age, duration, emotional distress and adherence to self-care, and scores for types 1 and 2 diabetics were comparable [58]. DCP scores differed by diabetes type and treatment. In types 1 and 2 patients combined, correlations with HbA1c were noted for three DCP scales—control problems, self-care ability, and self-care adherence. For type 2 patients not using insulin, three additional scales correlated with HbA1c, i.e., social and personal factors, negative attitude, and medical barriers [61]. Patients with glycemic control scored higher on the Personal Control Scale [35,38]. Treatment satisfaction as measured by the DTSQ was associated with lower HbA1c levels and better ratings of recent diabetic control [37].

Two disease-specific instruments, the DQOL measure [49] and the DQLCTQ [45], were developed specifically for trials of insulin-treated patients. The DQOL is the most widely used and accepted, but no significant differences between intensive and conventional treatment for type 1 diabetics were noted after 6.5 years of treatment. Two of the eight DQLCTQ scales significantly favored insulin lispro in crossover trials.

The DHS questionnaire was also created for a longitudinal study, but no significant changes were noted in the score after four months of life-style modification for weight control [64]. A Dutch version of the DHP, designed specifically for insulin dependent or requiring patients, was administered to patients in a 1-year intensive treatment study and some improvements were noted at one year [94]. Most other disease-specific instruments have been utilized in cross-sectional or validation studies only.

Condition-specific battery assessments have shown mixed results in clinical trials of type 2 diabetes patients. An advantage of a condition-specific battery is the ability to target assessments to patient characteristics, study designs, and anticipated outcomes. Unfortunately, reliability and validity of the battery in a type 2 diabetic population may be unknown. Additionally, it may be difficult to replicate results with other groups of patients, different study designs, or objectives.

Several experts have recommended that HRQoL evaluations include both generic and disease-specific measures to capture general health status as well as more disease-related concerns. Since psychological factors are important in diabetes, the addition of one of the psychological measures may provide valuable information not incorporated in the other instruments. Finally, symptom assessments allow the opportunity to examine relationships of HRQoL scores with patient perceptions of symptom frequency and severity as well as the impact of metabolic control on patient symptoms [76,95,96].

There is undoubtedly a need for continued research in this area. The examination of HRQoL in relation to various therapies will provide important information for patients and clinicians. Further study is also required to evaluate and prevent the long-term negative HRQoL effects associated with progression of this disease.

Acknowledgments

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Generic Instruments
  6. Diabetes-Specific Instruments
  7. Condition-Specific Battery Measures
  8. Psychological Functioning
  9. Factors Affecting HRQoL
  10. Discussion
  11. Acknowledgments
  12. References

Sources of funding: AstraZeneca, L.P. Special thanks are extended to Audra Boscoe for her valuable assistance in conducting literature searches and obtaining reprints for this review and to Teresa Zyczynski for supporting this project.

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  2. Abstract
  3. Introduction
  4. Methods
  5. Generic Instruments
  6. Diabetes-Specific Instruments
  7. Condition-Specific Battery Measures
  8. Psychological Functioning
  9. Factors Affecting HRQoL
  10. Discussion
  11. Acknowledgments
  12. References
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