Background:

Continuity of care is a fundamental attribute of primary care and has been associated with improved health outcomes. Its relationship with medication adherence, however, remains inconsistently demonstrated, largely due to methodological limitations, particularly the concurrent measurement of continuity and adherence. This issue is especially relevant in common chronic conditions managed in primary care—depression, hypercholesterolemia, and chronic obstructive pulmonary disease (COPD)—where long-term adherence to preventive pharmacotherapy is suboptimal.

Research questions:

Is higher longitudinal continuity of care during the first 12 months following a new diagnosis of depression, hypercholesterolemia, or COPD associated with higher medication adherence during the subsequent 12 months?
2. Does the association between continuity of care and subsequent medication adherence persist after adjustment for sociodemographic characteristics, comorbidity burden, and healthcare utilization during the continuity measurement period?

Method:

We will conduct a retrospective population-based cohort study using electronic medical records from a large integrated health system. Adults with newly diagnosed depression, hypercholesterolemia, or COPD will be included. Continuity of care will be measured during the first 12 months after diagnosis using validated indices (COCI and UPC). Medication adherence will be assessed in the subsequent 12 months using pharmacy refill data and expressed as the proportion of days covered (PDC ≥80%). Continuity and adherence periods will not overlap. Multivariable logistic regression will assess the association between continuity and later adherence, adjusting for sociodemographic factors, comorbidity burden, healthcare utilization, and physician-related variables, with condition-specific and sensitivity analyses.

Results:

We hypothesize that higher continuity of care during the first year after diagnosis will be independently associated with higher medication adherence in the following year across all three conditions.

Conclusions:

By enforcing strict temporal separation between continuity and adherence measurements, this study strengthens causal inference regarding the role of continuity of care in supporting medication adherence in common chronic diseases managed in primary care.

Points for discussion: