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Treatment adherence in patients with systemic lupus erythematosus (SLE) has been shown to be low, with approximately 30% never failing to take their medications (1–3), between 20% and 40% stopping their medication on their own (2), and between 14.0% and 42.6% missing one or more clinic visits (1, 4–6). Nonadherence may pose a severe problem, as it has been associated with higher morbidity (5), hospitalization (6), and poor renal outcome (7). Few studies have investigated treatment adherence in SLE patients and generalization of the results is often limited because rheumatoid arthritis (RA) and SLE patients were treated as one patient group (2, 8, 9) or differences between specific ethnic groups were investigated (1, 2, 8–10). Moreover, psychosocial factors that may predict treatment adherence in SLE patients have not been sufficiently investigated (11). The present study aimed at assessing treatment adherence in a representative cohort of SLE patients and investigating associations with psychosocial and medical factors.
SLE is an autoimmune disease that can result in inflammation of multiple organ systems at the same time. The worldwide prevalence is estimated to be approximately 1 per 1,000 and the female to male ratio is 10:1 (12). The course of disease is characterized by alternating periods of either relatively stable disease or high disease activity. In the face of an exacerbation, patients may need to take high doses of immunosuppressive agents. But also when the disease is relatively stable, maintenance doses are often required to preserve low activity and patients are closely monitored for signs of flare-ups. Therefore, treatment adherence is important to control the course of disease.
A comprehensive assessment of treatment nonadherence should involve both intentional and unintentional nonadherence (13). In the case of intentional nonadherence, patients actively choose not to follow treatment recommendations. A social cognition model that aims to explain intentional nonadherent behavior was developed by Horne (1997) (14) and is based on the Health Belief Model (15) and the Illness Perceptions Model (16). According to Horne's model, adherence to medication is based on a combination of a range of beliefs concerning perceived severity, susceptibility, benefits, and barriers, and patients' illness perceptions, i.e., their understandings of the nature of the illness, its severity, cause, timeframe, likely prognosis, and treatability.
In contrast to intentional nonadherence, unintentional nonadherence is thought to be the result of a passive process that is less strongly associated with individuals' beliefs and perceptions (13). Factors associated with unintentional nonadherence can be categorized according to the following 3 groups: 1) patient factors (e.g., age), 2) treatment factors (e.g., side effects), and 3) patient–health care provider factors (e.g., doctor–patient interaction) (13).
Problems with cognitive functioning are frequently reported in SLE patients. The prevalence of cognitive dysfunctions is not only high (i.e., 27–52%) in patients with past or present neuropsychiatric manifestations of SLE, but also 20–42% of patients without neuropsychiatric lupus show cognitive impairments (17). Two previous studies have looked at the association between medication adherence and cognitive functioning in SLE patients (1, 3). In both studies, the assessment of cognitive impairments was based on patients' performances on ability tests: reading ability and short-term memory in one study (1) and verbal learning and memory in the second study (3). Poor performance on short-term memory was associated with low adherence in African American patients, but not in white patients (1). However, the authors propose that this difference between ethnic groups is a result of socioeconomic disparity and it may not reflect a real barrier to adherence. Problems with verbal learning and memory did show a relationship to poor adherence, but were not important predictors after accounting for other variables (3). Contrary to measuring performance, the present study aimed to assess patients' self-reported problems in doing several cognitive functions and activities of daily life. From a clinical perspective, it is more informative to know which problems patients actually experience and how these real problems relate to nonadherent behavior.
The present study assessed intentional and unintentional treatment nonadherence in SLE patients. Moreover, we examined the associations between treatment nonadherence and sociodemographic and disease characteristics, cognitive functioning, and several psychosocial factors, including beliefs about medicines, illness perceptions, and emotional well-being.
- Top of page
- PATIENTS AND METHODS
- AUTHOR CONTRIBUTIONS
This study assessed the prevalence and predictors of intentional and unintentional treatment nonadherence in SLE patients. The high mean self-reported adherence level indicates good adherence, but patients also commonly report intentional or unintentional nonadherence. Unintentional nonadherence was more common than intentional nonadherence and was associated with nonattendance of clinic visits. Problems with cognitive functioning, concerns about potential adverse effects of medication, and age were the best predictors of nonadherence.
Treatment nonadherence has been identified as a substantial problem in patients with chronic inflammatory rheumatic diseases (32). However, few studies have focused on treatment nonadherence in SLE patients specifically and no prior studies have included self-report adherence questionnaires that have been validated for use in SLE patients. Previous studies that have assessed adherence in SLE patients report levels between 69.1% and 83% (2, 6, 10, 33, 34). Even though every study used a different measure to assess adherence, the mean adherence level of 86.7% found in the present study seems to be at the high end of the range. This may be partly explained by a difference in the regulation of the health care system. Three of the previous studies have been conducted in the US or Mexico, where costs of medication may be a barrier to adherence (2, 6, 33). This is less likely to be a problem for patients in New Zealand due to the publicly funded health care system. Health care costs have indeed been identified as potential threats to adherence for SLE patients in the US and developing countries (8, 35). Higher health care costs may also explain the difference in the percentage of missed clinic visits: 5.2% in the present study versus rates between 14% and 42.6% in previous studies (1, 4–6).
Only one known study, in which patients with RA and SLE were assessed together, has made the distinction between intentional and unintentional nonadherence (2). Two-thirds of patients reported forgetting their medication at least occasionally, and between 20% and 40% of patients said they intentionally did not take their medication at least occasionally (2). These results are comparable to the findings in the present study that both intentional and unintentional nonadherence were frequently reported and unintentional nonadherence seems to be more common.
Problems with cognitive functioning, more specifically with recognition/planning, were the strongest predictors of self-reported adherence level and unintentional nonadherence. Activities that pertain to recognition/planning are managing money and paying bills, remembering to take medication, and recognizing people. As mentioned before, two previous studies have looked at the association of cognitive functioning with adherence measures in SLE patients (1, 3) and both could not support a predictive effect of cognitive impairments. A study that looked at the relationship between adherence and cognitive impairments in 3 different patient groups does propose that cognitive dysfunctions may identify patients at risk of poor adherence regardless of diagnosis or regimen (36).
Concern about potential adverse effects of medication was the second most important predictor of unintentional nonadherence and the only predictor of intentional nonadherence. Although most studies on treatment adherence in SLE patients have also looked at associations with sociodemographic and psychological factors, only few have used validated questionnaires to measure these variables (1, 2, 33). Despite this limitation, fear of side effects of medication was an important barrier to adherence in 5 of 6 studies (1, 2, 8, 10, 35).
Age was a third significant predictor of self-reported adherence level and unintentional nonadherence. One other study has examined the relationship between age and adherence in SLE and found a nonsignificant tendency for adherent patients to be older than nonadherent patients (33). A similar effect of age on adherence has been reported in a study investigating predictors of adherence in 4 chronic illnesses (37).
Adherence measures did tend to differ between ethnic groups, with patients from the Pacific Islands reporting lower adherence and missing more clinic visits than patients from the other ethnicities. However, ethnicity was not a significant predictor on the basis of regression analyses. Previous studies have reported mixed results on the relationship between ethnicity and adherence levels, and comparison with the present study is limited because prior research involved different ethnic groups. Three studies report a lower self-reported adherence in African Americans compared with whites (2, 5, 33), but one study used a physician's assessment of adherence (5) and another study only found an effect for hydroxychloroquine, and not for prednisone or other immunosuppressants (33). Studies that involved the same ethnic groups as the present study, but looked at medication adherence in patients with diabetes mellitus, support a poorer medication self-care (38) and lower adherence rates (39) in Pacific peoples compared with Europeans.
Although 3 previous studies have found a relationship between adherence and education (2, 33, 34) and 2 studies found a relationship between adherence and marital status (2, 33), the present study could not confirm these results. Similarly, none of the disease characteristics (disease activity, disease duration, number of comorbidities, number of involved organs, and number of medications) were related to measures of adherence. However, the disease activity index that was used in the present study, the SLEDAI, may have failed to detect a relationship with adherence because of a lack of the inclusion of subjective symptoms. For instance, the assessment of fatigue is not part of the SLEDAI but has been identified as a highly prevalent and disturbing symptom (40). Other indices, such as the European Consensus Lupus Activity Management (41), do include these subjective measures and may be better correlated with adherence measures.
The high prevalence of unintentional nonadherence and its association with missing clinic visits suggests that a primary focus on reducing unintentional nonadherence would greatly improve treatment adherence. This approach is supported by findings from a previous study in which the main self-reported barriers to adherence among SLE patients were examples of unintentional nonadherence (e.g., “just having forgotten” or “being busy at work”) (33). In addition, suggestions by these patients on how to improve adherence all referred to actions that are related to preventing unintentional nonadherence (e.g., pill boxes or task lists). Apart from these direct methods to reduce unintentional nonadherence, adherence can be further improved indirectly by resolving problems with cognitive functioning and concerns about adverse effects of medication. A recent study found a significant improvement in cognitive functioning of SLE patients after an 8-week psychoeducational intervention (42). With regard to concerns about possible side effects, addressing a patient's specific concerns may not only reduce fear of adverse effects and thereby improve adherence, but it may also improve the doctor–patient relationship. Problems with communication and trust have been identified as important barriers to adherence in SLE patients (1, 8, 10, 33).
A limitation of this study is that it was cross-sectional and correlational, which limits interpretations about causality. In addition, several potential barriers to adherence were not investigated. For instance, assessment of the patient–doctor relationship (1, 10, 33), perceived costs and evaluation of the health care system (8, 10), and frequent dosing of medication (8, 33) have been identified as a threat to adherence but were not assessed in the present study. Also, the majority of patients were of New Zealand European origin, which limits comparisons between different ethnic groups. A substantial proportion of SLE patients of Asian origin could not be included in the study because of language barriers. Finally, there is a potential selection bias because the participating group and nonparticipating group could not be compared.
In conclusion, intentional and unintentional nonadherence are common in SLE patients. Adherence measures were associated with age, cognitive functioning, and illness-related emotions. Nonadherence may be reduced by targeting cognitive functioning and by fine tuning doctor–patient communication to address patients' individual concerns about their medications.