• Seung Jae Kim, Oh Deog Kwon, Eunice Bormee Han, Cheol Min Lee, Seung-Won Oh, Hee-Kyung Joh, Bumjo Oh, Hyuktae Kwon, BeLong Cho, and Ho Chun Choi.
• Department of Family Medicine, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul.
• Medicine (Baltimore). 2019 Dec 1; 98 (49): e17825e17825.

AbstractThis study tried to investigate the effects of number of medications and age on antihypertensive medication adherence in a real-world setting using a nationwide representative cohort.We obtained data from the National Health Insurance Service-National Sample Cohort (NHIS-NSC) of Korea, which is a sample of 2.2% (N = 1,048,061) of total population (N = 46,605,433). Patients aged 20 years or older (N = 150,550) who took antihypertensive medications for at least 1 year were selected. Medication possession ratio (MPR) was used for measuring adherence. The subjects were divided into 5 subgroups according to total number of medications: 1-2, 3-4, 5-6, 7-8, and 9 or more. The mean age and the mean number of medications were 60.3 ± 12.6 years and 4.1 ± 2.2, respectively. The mean MPR was 80.4 ± 23.9%, and 66.9% (N = 100,645) of total subjects were adherent (MPR ≥ 80%). The overall tendency of antihypertensive medication adherence according to the total number of medications displayed an inverted U-shape with a peak at 3-4 drugs. Adherence consistently increased as the age increased until age 69 and started to decrease from age 70. The proportion of adherent patients (MPR ≥ 80%) according to the total number of medications also showed an inverted U-shape with a peak at 3-4 drugs. When the same number of drugs was taken, the proportion of adherent patients according to age featured an inverted U- shape with a peak at 60 to 69 years. Patients taking 9 or more total drugs had the overall odds ratio (95% CI) of non-adherence (MPR < 80%) with 1.17 (1.11-1.24) compared with those taking 1 to 8 total drugs and the odds ratios in the age subgroups of 40 to 49, 50 to 59, 60 to 69 years were 1.57 (1.31-1.87), 1.21 (1.08-1.36), and 1.14 (1.04-1.25), respectively (P < .05).Association between age, total number of medications, and antihypertensive adherence displayed an inverted U-shape with a peak at 3 to 4 total medications and at age 60 to 69 years. When the total number of drugs was 9 or more, adherence decreased prominently, regardless of age.

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