Impact of age on long-term anticoagulation and how gender and monitoring setting affect it: implications for decision making and patient management.

Abstract

Stabilization of anticoagulation control is seminal to reducing the risk of adverse effects of vitamin K antagonists. Reliable information on how ageing influences this is lacking. We set out to assess the true age-related changes in anticoagulation control, how gender and patient setting influence this, and the possible implications of these for patient outcomes and management. In atrial fibrillation (AF) patients of a unified anticoagulant service monitoring patients in general practice or hospital-based clinics and housebound patients at home, international normalized ratio (INR) and warfarin dose data between 2000 and 2013 were extracted via the DAWN dosing program. Anticoagulation control was assessed by calculating percentage time spent within target INR (TTR). A total of 2094 AF patients [938 (44.8%) in general practice (GP) and 531 (25.4%) in hospital (H)-based clinics and 625 (29.8%) through the domiciliary service (D)] were evaluated. The frequency of warfarin dose changes and INR monitoring events declined until about age 67, then increased as patients got older. The TTR according to age was significantly lower and the probability of having a TTR≤65% according to age was higher for D than for H and GP, and females had a greater probability of having a TTR ≤65% than age-matched males. Identification of factors underlying poorer anticoagulation control in older housebound patients and the introduction of effective modifications to improve the clinical effectiveness of anticoagulation in such patients is needed.