Background: More than 50% of patients are non-adherent to medications, often without an easily identifiable reason to clinicians. No study has quantified the extent to which health behaviors like medication-taking are correlated within families using national or routinely collected data for a range of conditions.
Objective: To examine how an individual's health behaviors are influenced by those of their family members, particularly in adherence to medications for chronic conditions.
Design: Retrospective cohort study.
Patients: Using claims from a large nationwide insurer, we identified patients initiating medications for one of five chronic conditions with a family member who also recently filled one of these medications.
Main measures: The primary exposure was whether family members were fully adherent (defined as a proportion of days covered ≥ 80%) before the patient's date of initiation. The outcome of interest was whether patients were fully adherent in the 12 months after initiation. Baseline demographic and clinical characteristics were also measured before initiation. We used multivariable modified Poisson regression to examine the association between prior family adherence and subsequent patient adherence.
Key results: Among 254,144 patients, rates of full adherence among patients whose family members were and were not fully adherent were 37.3% and 26.9%, respectively (adjusted relative risk [aRR] 1.29, 95%CI 1.28-1.31). The association was stronger when both used cardiometabolic medications (aRR 1.35, 95%CI 1.32-1.37). Similarly, patients were also 38% more likely to be adherent if they and their family members used a medication for the same condition (aRR 1.38, 95%CI 1.35-1.40).
Conclusions: Adherence among family members appeared to be highly correlated, suggesting positive reinforcement by family or the sharing of unmeasured behaviors or characteristics associated with better adherence. Regardless, information about prior adherence among family members from routinely collected data could potentially inform adherence prediction or intervention efforts.
Keywords: chronic disease; health behavior; medication adherence; social contagion; social reinforcement.