Barriers to and Determinants of Medication Adherence in Hypertension Management: Perspective of the Cohort Study of Medication Adherence Among Older Adults

Abstract

Low adherence to antihypertensive medication remains a public health challenge. Understanding barriers to, and determinants of, adherence to antihypertensive medication adherence may help identify interventions to increase adherence and improve outcomes. The Cohort Study of Medication Adherence in Older Adults (CoSMO) is designed to assess risk factors for low antihypertensive medication adherence, explore differences across age, gender, and race subgroups, and determine the relationship of adherence with blood pressure (BP) control and cardiovascular outcomes over time. Between August 2006 and September 2007, 2194 participants, age 65 years and older, taking antihypertensive medication were recruited and enrolled in CoSMO and completed a baseline telephone survey. Antihypertensive medication adherence was assessed with the Morisky Medication Adherence Scale (MMAS) and the medication possession ratio (MPR). Low adherence was defined as a MMAS score < 6; non-persistent MPR was defined as <0.80. BP data were abstracted from outpatient electronic medical records; uncontrolled BP was defined as systolic or diastolic BP ≥140 or 90 mmHg, respectively. The mean age of participants was 75.0 ± 5.6 years, 58.8% were women, 30.7% were black, and 83.6% were taking 2 or more classes of antihypertensive medication. Overall, 14.1% of participants had low adherence, 27.0% had a non-persistent MPR, and 33.7% had uncontrolled BP. Participants with low MMAS were 2.71 (95% confidence interval (CI) 2.31-3.18) times more likely to have non-persistent MPR and 1.20 (95% CI 1.00-1.43) times more likely to have uncontrolled BP than participants with high MMAS. Low antihypertensive medication adherence and uncontrolled blood pressure are common in older, insured patients. Research identifying barriers to achieving antihypertensive medication adherence may assist in developing tailored interventions to increase medication adherence and improve outcomes.

Antihypertensive Medication Adherence and Risk of Cardiovascular Disease Among Older Adults: A Population‐Based Cohort Study

“…The attenuation in risk reduction was mainly attributed to the reclassification of 44% (n=20 735) of beneficiaries with intermediate adherence (40–79%) under ≥1 antihypertensive available PDC to ≥80% category using the first‐year PDC. Many studies suggested that the average medication adherence declined significantly over time with the greatest changes within first year of treatment 5, 8, 9, 11, 20. Our results suggested that the use of first‐year PDC might not reflect well the long‐term adherence behavior, and the longer‐term PDC might capture better the association between PDC and CVD outcomes among the older beneficiaries.…”

“…Of the 94 617 beneficiaries with ≥80% adherence under ≥1 antihypertensive available PDC, 35 988 (38%) had been reclassified to 40% to 79% category under the average PDC, which might result in the gradual risk reduction under average PDC method. The prevalence of discontinuation or switching to different classes of antihypertensives were common among newly initiated patients, especially during the first year 5, 8, 9, 11, 20. Many of those patients, especially the older patients, might likely be adherent, but discontinued the initial medications because of the side effects or switching to other medications for better blood pressure control, and the average PDC method might misclassify as nonadherent some adherent patients 29.…”

“…Antihypertensive adherence might be a particular concern for older adults who have multiple chronic conditions 4, 5, 6, 8, 20. Many studies have examined major barriers and predictors of nonadherence among hypertensive patients,5, 7, 9, 11, 44, 45 and some focused on older adults 6, 46. Potential barriers to adherence among older adults can be classified into 3 categories: (1) patient‐related factors, including sociodemographics, psychosocial factors, comorbidities, cognitive ability, and health beliefs; (2) medication‐related factors, including the number of medications taken, adverse side effects, and complex medication regimens; and (3) other factors, including the patient‐prescriber relationship, access to medication and cost, and social support 6, 46.…”

“…Many randomized, control trials demonstrated the benefit of antihypertensive medications (antihypertensives) on reduction of risk for CVD morbidity and mortality 2, 3. Despite the benefit of antihypertensive therapies, many studies suggested suboptimal adherence to these medications, particularly among older adults with multiple chronic conditions 4, 5, 6, 7, 8, 9, 10, 11. Nonadherence to antihypertensives is associated with increased risk for CVD, hospitalization, and healthcare costs 5, 12, 13, 14, 15, 16, 17.…”

Medication Adherence Does Not Explain Black-White Differences in Cardiometabolic Risk Factor Control among Insured Patients with Diabetes

“…1,2,[8][9][10][11][12][13][14][15][16][17][18][19][20] Prior research has consistently found racial differences in medication adherence. [21][22][23][24] The reasons underlying such differences are poorly understood, but are often thought to stem from differences in care access, care quality, and selfmanagement behaviors. 18 As medication non-adherence is associated with poor cardiometabolic risk factor control among patients with diabetes, [8][9][10][11][12][13][14] it has been suggested that differences in medication adherence may be responsible for subgroup differences in risk factor control among patients with diabetes.…”