The association of severity of airflow limitation with adherence to oral medications in Veterans with hypertension and/or diabetes
Diabetes and Hypertension are common among patients with Airflow Limitation and contribute to Cardiovascular (CV) mortality, one of the leading cause of death among patients with airflow limitation (AFL). We examined the association of severity of AFL with adherence to medications for hypertension and diabetes.
We identified 7,359 Veterans with hypertension and/or diabetes in the Veterans Integrated Service Network-20. Entry date into the cohort was defined as the date of a patient’s first pulmonary function testing (PFT). Diagnostic codes (ICD-9), PFT, and pharmacy data were available via the electronic medical record or via direct interrogation of PFT equipment. Our primary exposure was AFL defined as an FEV1≥80% predicted (normal), FEV1 50-<80% predicted (mild/moderate), FEV1 30-<50% predicted (severe), and FEV1<30% predicted (very severe). We assessed adherence using a validated method based on electronic pharmacy refill data and defined adherence as ≥80% medication possession for the period 6-12 months after enrollment. Medications of interest included beta blockers (BBs), calcium channel blockers (CCBs), thiazides, and ACE inhibitors (ACEIs) for patients with hypertension, and metformin and sulfonylureas for patients with diabetes. We utilized logistic regression models to assess the association between severity of AFL and adherence, adjusted for demographics, health behaviors, and comorbidities.
Overall adherence was poor (44.6-55.1%). Among patients with hypertension, when compared to subjects with normal FEV1, subjects with each category lower of FEV1 were less adherent to BBs, with OR of 0.87 [95% CI, 0.80-0.95], CCBs, with OR of 0.83 [95% CI, 0.74-0.93], and ACEIs with OR 0.91 [95% CI 0.84-0.99]. AFL was not associated with adherence to thiazides. Among patients with diabetes, we found no significant association of FEV1 with adherence, though a similar lower trend with increasing AFL. In a sensitivity analysis limited to patients with COPD, we found a non-statistically significant trend for decreased adherence to BBs, CCBs and ACEIs in subjects with higher GOLD stage.
Severity of AFL is associated with decreased adherence to BBs, CCBs and ACEIs. The decreased adherence to these medications may be related to adverse effects on symptoms in patients with lung disease, and may partially explain excess CV mortality in these patients.