The association between continuity of primary care and both initiation and adherence of common cardiovascular medications

Problem

Longitudinal continuity of primary care, and prescribing of and adherence to medication, are both crucial aspects of primary healthcare, but the relationship between them has not previously been studied in detail. This study tested the primary hypothesis that better continuity of care is associated with increased prescribing of clinically relevant medication and improved medication adherence, and the secondary hypothesis that perfect continuity is less strongly associated with prescribing and adherence than good continuity.

Approach

We used a random sample of 300,000 patients aged 30+ in 2017 within 83 English GP practices from the Clinical Practice Research Datalink. The hypotheses were tested in patients in five specific cardiovascular-related therapeutic areas. Adjusted associations between continuity of care, medication use, and adherence were examined using logistic regression. Continuity of Care index was calculated for 173,993 patients with 4+ GP consultations two years prior to their index date and divided into five categories: absence of continuity, below-average, average, above-average and perfect continuity. Medication usage outcomes were calculated for both initiation and adherence for statins (primary or secondary prevention separately), anticoagulants, antiplatelet agents, and antihypertensives. Adherence was estimated as medication possession ratio >80%.

Findings

There was strong evidence (p<0.01) that initiation of cardiovascular medications varied with continuity of care. Patients with absent continuity were less likely to be prescribed cardiovascular medications than patients with above-average continuity (statin primary prevention OR 0.71, 95%CI 0.59-0.85; statin secondary prevention 0.77, 0.57-1.03; antiplatelets 0.55, 0.33-0.92; antihypertension 0.51, 0.40-0.65). Similar findings were observed for those with below-average continuity (statin primary prevention OR 0.90, 95%CI 0.81-1.00; anticoagulants 0.79, 0.68-0.92; antihypertension 0.69, 0.61-0.78) or average continuity (antihypertension 0.89, 083-0.97). Patients with perfect continuity were more likely to be prescribed cardiovascular medications than those with above-average (statins primary prevention OR 1.23, 95%CI 1.01-1.49; statin secondary prevention 1.36, 1.10-1.71; antiplatelets 1.38, 1.08-1.74; antihypertension 1.10, 0.99-1.23).In contrast, continuity of care was generally not associated with medication adherence, although there was modest evidence (p=0.03) that adherence to statins for secondary prevention varied with continuity; patients with average continuity showed poorer adherence than above-average continuity (OR 0.74, 95%CI 0.60-0.94).

Consequences

Better continuity of care may increase prescribing of appropriate medication for patients at higher risk of cardiovascular disease, but is only weakly associated with patients' adherence to these medications.