Medication-related harm due to non-adherence may explain the relationship between polypharmacy and mortality

Introduction\ud Strong evidence exists for a relationship between polypharmacy and mortality[1], independent of comorbidity. The mechanisms underlying this relationship are unclear. Medication-related harm (MRH) may occur due to non-adherence or adverse drug reactions. We sought to determine if MRH due to non-adherence or adverse drug reactions may explain the association between polypharmacy and mortality.\ud \ud Methods\ud The PRIME study recruited 1280 older adults at hospital discharge from 5 hospitals in England between 2013 to 2015[2]. Patients were followed up in the community for 8-weeks by senior pharmacists to identify MRH using data from hospital readmissions, GP records and patient interviews. Mortality data at 12 months post-discharge were obtained from hospital records. Non-adherence was determined using a modified version of a validated questionnaire[3]. Adverse drug reactions were assessed using the Naranjo algorithm[4]. Adjusted logistic regression models were used to investigate the relationship between (1) number of medicines and MRH, (2) MRH and mortality.\ud \ud Results\ud 1116 out of 1280 patients completed follow-up (median age 82 years, range 65-103 years, 58% female). Patients were discharged with a median of 9 medicines (range 0-27). A higher number of medicines was strongly associated with MRH due to non-adherence (p