Background: Efficacy and safety of vitamin K antagonists (VKAs) depend on quality of anticoagulation control, usually measured as time in therapeutic range (TTR). Factors that predict low TTR on VKAs could be used to identify patients who might benefit from interventions, or who would be better treated with a non-VKA oral anticoagulant (NOAC). Patients living alone may have difficulties in taking their medications, managing their diets, or coming to clinic for monitoring.
Purpose: To assess influence of cohabitation status on TTR with VKA among men and women.
Methods: We identified all Danish patients with atrial fibrillation (AF) who initiated VKA between 1997 and 2012, and studied patients who had 6 months of continuous VKA use and international normalized ratio (INR) monitoring. Patients were divided according to sex and whether they lived alone or with others. We calculated TTR using the Rosendaal method, and INR variability using Fihns method. We used a linear regression model to test for associations between TTR and covariates, and adjusted for age, income, medications and comorbidities.
Results: We identified 4,772 AF patients with 6 months of continuous VKA use and INR monitoring. 713 (15%) were men living alone, 1,073 (23%) were women living alone, 2,164 (45%) were men not living alone and 822 (17%) were women not living alone. INR was measured a median of 11 (interquartile range 8–15) times during the 180 days of VKA use, but men who lived alone had 0.6 (95% confidence interval (CI): 0.2 to 1.2) fewer INR measurements during the period. Median TTR was lowest among men living alone (57.2%), followed by women living alone (58.8%), women not living alone (61.0%) and men not living alone (62.5%). After multivariable adjustment, men who lived alone had a 3.6% (CI −5.6 to −1.6) lower TTR compared with men not living alone, but women who lived alone did not have significantly lower TTR (P=0.80) compared with women not living alone. Living alone had significantly greater effect on TTR among men than among women (interaction P=0.02). Men living alone also had higher adjusted INR variability (0.2, CI 0.0 to 0.4) compared with men not living alone.
Conclusion: Living alone was significantly related to low quality of anticoagulation control among men, but not among women.