The epidemiology of polypharmacy in a large cohort with linked health records in Scotland

Abstract

Abstract Background Our understanding of the potential harm of taking multiple medications in older, multi-morbid populations is limited. We aimed to investigate the prevalence of polypharmacy and its association with hospitalisation in a large cohort with linked health data. Methods Prescription data and hospital admission records of the Aberdeen Children of the 1950s (ACONF) Cohort were extracted from the National Health Services Scotland database and linked from 2011-2016. We estimated polypharmacy by measuring monthly drug exposure for 1) total number of prescribed medications and 2) total number of defined daily doses (DDDs). Cox proportional hazard models (adjusted for demographics, socioeconomic circumstances and health conditions) were used to examine the association of polypharmacy and hospitalisation. Results Prescription records were linked for 8,713 cohort members. Mean age at baseline was 58.5 years (SD = 1.5) and 50% were female. 1,994 individuals (23%) had at least one health condition and 8% of population had multimorbidity. The proportion of cohort with polypharmacy assessed using taking 5+ medications and taking 5+ DDDs at baseline were 12.7% (female=12.6% vs male=12.7%, P = 0.179), and 15.5% (female=13.8% vs male=17.1%, P < 0.001) respectively. Of all the cohort, 4,365 admitted to hospital (mean follow-up of 3.5 years, total 30,269 person-years). Adjusted hazard ratios for hospitalisation were 1.51 (95 % CI 1.39,1.64, P < 0.001) for polypharmacy measured by number of medications and 1.40 (95 % CI 1.29,1.51 P < 0.001) for polypharmacy estimated by number of daily doses. Conclusions Polypharmacy is independently associated with increased risk of hospitalisation. This association could signify polypharmacy as a risk factor and a marker of poor outcome. Data linkage can generate evidence-based information for future policy and health services to improve polypharmacy measurement and management. Key messages Data linkage is a cost effective and contemporary return on the investment in data collection and research in public health. Improvement in evidence to better understand the relationship between polypharmacy and health outcomes should be a priority to optimise treatment in older people with various chronic conditions.