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J Clin Hypertens (Greenwich). 2012; 14:429–434. © 2012 Wiley Periodicals, Inc.
The aim of this study was to validate a French translation of the structured self-report 8-item Morisky Medication Adherence Scale (MMAS-8) and determine its psychometric properties in patients taking antihypertensive medication. An observational cross-sectional study was conducted in the hypertensive unit of a French university hospital. The MMAS-8 was translated according to international guidelines. Internal consistency was assessed using Cronbach α coefficient, construct validity using principal component and confirmatory factor analyses, and the test-retest reliability at 1-month interval using the intraclass correlation coefficient (ICC). Three levels of adherence were considered (low: scores of 0 to <6; medium: 6 to <8; high: 8) and risk factors were explored in ordinal logistic regression models. A total of 199 patients were included: mean age, 55.7±14.6 years, 57.3% men (114 of 199), and 39.5% (66 of 167) had uncontrolled blood pressure. The French MMAS was moderately reliable (α=0.54), one-dimensional, and reproducible (ICC=0.68). The mean score was 6.96 (standard deviation 1.25) and 17.6% (35 of 199), 37.7% (75 of 199), and 43.7% (87 of 199) of patients had low, medium, and high adherence, respectively. The only factor significantly associated with adherence was age. The French MMAS has acceptable psychometric effects to measure medication adherence in hypertensive patients and may be useful in detecting nonadherent hypertensive patients.
Adherence to antihypertensive medication is a key determinant of adequate blood pressure (BP) control and prevention of cardiovascular outcomes.1 Several studies have underlined the association between low adherence to antihypertensive drug therapies and uncontrolled hypertension.2 In a study by Mazzaglia and colleagues,3 high adherence was associated with a 38% decreased risk of cardiovascular events compared with lower adherence. Nevertheless, according to various studies, the percentage of adherent patients varies from 50% to 70%.4 In France, an epidemiologic study demonstrated that 49% of treated patients had persistent high BP,5 the main reason for which, according to some authors, is nonadherence to antihypertensive drug therapies.
Identifying adherence-related behaviors of hypertensive patients is an important step towards improving compliance and patient education and, for this, numerous direct and indirect tools have been proposed. However, to date, no tool has been identified as the gold standard and no single scale is appropriate for every setting. The information gained from measurement of adherence can help to achieve optimum outcomes. Adherence measurement should be accurate and allow understanding of patients’ adherence barriers to their medication.6 The choice of the specific measure used in clinical practice depends on the intended use of the information, the resources available to the provider, and the patient’s acceptance and convenience of the method.7 Currently, adherence is determined by self-reported assessment and through interviews conducted during office visits. Self-reporting methods include patient-kept diaries of medication-taking and responses to adherence-specific questionnaires.
The second most commonly used adherence-specific self-report questionnaire in the literature6 is the Morisky Medication Adherence Scale (MMAS).8 The reliability and validity of this scale was originally established as a 4-item questionnaire in patients with hypertension and then used for numerous chronic disorders. Advantages of the MMAS include simplicity of the questions and ease of scoring. It has recently been expanded with 4 additional items addressing the circumstances surrounding adherence behavior.9 The updated version of the MMAS (MMAS-8) has better psychometric properties than the original 4-item version. Scores obtained from this scale range from 0 to 8, where higher scores indicate higher adherence.
Reviewing properties of the tools, such as simplicity of administration and scoring, reliability, generalizability, and sensitivity/specificity, as well as validation populations, is a crucial step when selecting a questionnaire. The MMAS-8 has been adapted in Thailand and Malaysia for diabetes patients10,11 and in Sweden for human immunodeficiency virus–positive patients.12 However, no French version of the MMAS-8 has been validated to date. Translation, cross-sectional adaptation and validation of the MMAS in French are prerequisites to its routine use in clinical practice. Furthermore, development of a French version of MMAS-8 would allow French investigators to participate in international research studies when this scale is proposed.
The main objective of this study was to validate a French translation and culturally adapted version of the MMAS-8 and to examine its psychometric properties in patients with hypertension. The secondary objectives were to use the French MMAS to measure adherence of hypertensive patients treated with anti-hypertensive medications and to explore factors associated with nonadherence.
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This study reports on the development and the psychometric properties of the MMAS-8 translated and adapted to the French language. The French MMAS displays acceptable psychometric properties: the scale was one-dimensional, reproducible (ICC=0.68 [0.63–0.72]), and the reliability was moderate (Cronbach α=0.54; 95% CI, 0.44–0.63). Most of the included patients were highly adherent, and age was significantly associated with adherence.
In the present study, the French MMAS was validated in hypertensive patients as it was for the original MMAS-8. Compared with the MMAS-8, the psychometric properties of the French MMAS seemed to be lower, especially for internal consistency. One explanation might be due to differences in the population studied during the development of the original MMAS-8: our patient sample size was lower, there were more men, and more patients had high adherence. Like the original MMAS-8, the French MMAS structure analysis disclosed a single dimension; however, item 5 had a low factor loading. This is probably due to a recall bias because the item questions patients about their medication intake of the day before. The moderate internal consistency reliability we found is similar to that of two other studies that validated Thai and Malay versions of the MMAS-8 in diabetes patients.10,11 Test-retest reliability is correct for all the MMAS-8 translations. Contrary to Morisky and colleagues,9 we did not find a significant link between adherence and BP control. Thai and Malaysian versions, validated among diabetic patients, did not also find a strong link between glycemic control and adherence scores. Our result could be explained by the characteristic of our population with a lower number of included patients than Morisky and colleagues and a higher proportion of adherent patients.
Exploratory analysis of risk factors of nonadherence by multivariable modeling indicated a significant association between age and adherence (a decrease in risk of lower adherence for older patients). In the Thai and Malaysian studies, mean patient age was highest in the high adherence group. After adjustment for age, Morisky and colleagues found that knowledge, patient satisfaction, coping, stress level, and medication complexity were significantly associated with adherence. Similar to our results, the study by Fodor and colleagues19 conducted in three European countries, showed that younger patients were less likely to be adherent with antihypertensive drugs, and that is in accordance with numerous data in the literature.20,21 In the present study, the duration of treatment and the number of antihypertensive classes were associated with a lower adherence.
As in other studies about medication adherence, smokers tend to be less adherent. Some authors suggest that individuals who do not have a healthy lifestyle are less likely to adhere to a treatment regimen on a long-term basis.21
Acknowledgments and disclosures: The authors wish to thank the staff of hypertension ward for their active collaboration, Céline Itié and the nursing staff, François Boutouyrie and Pia Johansen for their participation in the translation of the questionnaire, the various contributors from the Unité de Recherche Clinique of the Hôpital Européen Georges Pompidou (Noël Lucas [medical coordinator], Yann Guivarch [financial account manager], Angéline Courquin [clinical trial coordinator], and Kévin Masini [data manager]), and the Direction de la Recherche Clinique et du Développement (DRCD of AP-HP) for sponsoring the study. The authors thank especially DE Morisky who gave the permission for use of the ©MMAS-8 for this study. Use of the ©MMAS is protected by US copyright laws. Permission for use is required. Licensure agreement is available from: Donald E. Morisky, ScD, ScM, MSPH, Professor, Department of Community Health Sciences, UCLA School of Public Health, 650 Charles E. Young Drive South, Los Angeles, CA 90095-1772. This study was funded by a grant from the Assistance Publique – Hôpitaux de Paris (Direction de la Recherche Clinique et du Développement: Programme Hospitalier de Recherche Clinique Régional AOR10033 – NI09036).