This study examines the association of medication adherence with blood pressure control status among outpatients in primary health care facilities. It was evident that low adherence was significantly associated with uncontrolled blood pressure. Reciprocally, poor blood pressure control was significantly associated with non-adherence to antihypertension treatment. In line with this finding, several studies reported that highly adherent patients were more likely to have controlled blood pressure than those with lower adherence [19,20,21]. Although the proportion of adherent patients was high (77.65%), clinical consequences of suboptimal medication adherence are negligible, including uncontrolled blood pressure, accelerating disease progression, and increasing hospital admissions due to cardiovascular complications [22].
In this study, we could not find any significant association between medication adherence and patient characteristics (age, sex, type of therapy, educational level, and the presence of comorbidity) in both statistical analyses. In contrast, ample studies proved many independent predictors related to medication adherence. For instance, Khayyat et al. [21] reported that sex, age, and the presence of comorbid other diseases such as diabetes mellitus affect medication adherence. In another study by Kang et al. [23], it is stated that medication adherence has an association with age and the presence of family members, but not with sex, usage duration, and blood pressure.
Then, the comorbidities accompanying hypertension were not associated with poor medication adherence and uncontrolled blood pressure (Tables 4 and 5). Opposed to this finding, several studies revealed that comorbidities such as diabetes mellitus, heart disease, and dyslipidemia affect patient adherence due to the consumption of more complex medications [24,25,26].
Patient adherence to their antihypertensive drugs indeed affects blood pressure control. However, other predictors of blood pressure control were found in the present study, such as age and education (Table 5). The patient’s age was inversely associated with uncontrolled blood pressure. The youngest group of patients (20–40 years old) were almost six times more likely to have uncontrolled blood pressure compared to those aged >60 (AOR: 5.809; 95% CI: 1.516–22.264; P = 0.010) (Table 5). It may be assumed that uncontrolled blood pressure in these particular age groups correlates with their adherence level percentage. In the oldest patients group, adherence level was 81.82%, whereas in the age group of 41–60 years old was 75.55% and even lower in 20–40 years old with 73.68%, even though the difference was not significant. Furthermore, Choi et al. [24] stated that patients aged >50 years had high adherence to the consumption of antihypertensive drugs. Older patients usually have a caregiver who helps take their medication and maintain a healthy lifestyle, thus control blood pressure eventually [23]. Moreover, older age was associated with better medication adherence due to perceived vulnerability and disease severity [27, 28].
The level of education in this study is known not to affect medication adherence or blood pressure control based on the chi-square test. However, multivariable logistic regression found that patients educated up to middle school had higher blood pressure control than college graduates. Other studies also showed inconsistent results. Ayodapo et al. [29] reported that educational level has no considerable effect on medication adherence, while Adisa et al. [30] showed a statistically significant correlation between medication adherence and education. Generally speaking, patients now have unlimited access to information regarding hypertension and the importance of medication adherence from websites, mobile applications, and health workers or pharmacists.
The success of hypertension therapy is influenced by adherence and other factors, such as lifestyle, physical activity, diet, sleep patterns, body mass index, smoking status, and stress [31]. Those factors were not observed in the present study due to data availability and time limitations. Another limitation involves the measuring adherence method (self-reported pill count). This method is subjective and may be inaccurate because the patient might remove the drugs from the container in anticipation of adjusting the number of the drug according to the medication schedule [7, 11, 17]. Besides, the number of respondents was limited, and the distribution of Puskesmas did not represent the whole city. So, it is necessary to add the number of respondents from many more Puskesmas for future study.
