For hypertensive patients with comorbidity, the number of comorbidity is associated with the pattern of their medication adherence

Type of funding sources: None.

Although medication adherence is an important self-care activity for hypertensive patients, their medication adherence is not often optimal. When patients with hypertension have comorbidities, they are asked to adhere to medications prescribed for all of their conditions, resulting in a greater burden. Some may decide to take medications for conditions they prioritize, while others may take all medications as prescribed. It is possible that the number of comorbidity affect the pattern of the patients’ medication adherence.

To examine if the number of comorbidity is associated with the medication adherence pattern in patients with hypertension and at least one of the following comorbidity related to poor outcomes in hypertensive patients: diabetes, hyperlipidemia, ischemic heart disease and stroke.

A secondary data analysis was conducted using the 2018 Korea Health Panel Survey, including 2218 hypertensive patients with at least one of the following comorbidity: diabetes, hyperlipidemia, ischemic heart disease and stroke. Two types of medication adherence was assessed: primary (i.e., filling prescriptions of medications prescribed by clinicians) and secondary medication adherence (i.e., taking medications as directed). Patients were divided into three groups based on the patterns of primary and secondary medication adherence in each comorbidity (Figure 1). Multinomial logistic regression was used to determine whether the number of comorbidity was associated with the medication adherence pattern after controlling for relevant covariates (i.e. age, gender, marital status, income level, education level, unmet medical needs and presence of primary care providers).

A total of 2218 patients (mean age 70.1, female 58.7%) had an average of 1.5 comorbidities (SD: 0.7); 10% had three or more comorbidities. About four-fifths of the patients (84.9%) were adherent to medications for all their chronic conditions (i.e., adherent group), 11% partially adhered to their medications (i.e., suboptimal group) and 4.1% did not adhere to any medications (i.e., non-adherent group). Compared with the adherent group, the suboptimal group were more likely to have a greater number of comorbidities after adjusting for covariates (adjusted odds ratio [aOR]=1.46). On the other hand, compared with the adherent group, the non-adherent group were more likely to have a smaller number of comorbidities (aOR=0.54).

Our study showed that an increased number of comorbidity is a risk factor for inconsistent medication adherence. However, since we also found that patients with a smaller number of chronic conditions were likely to be non-adherent to all medications, hypothesizing that increased number of comorbidity is associated with medication non-adherence may have been simplistic regarding these patients. The unexpected findings of non-adherent group needs to be further explored.