Impact of drug burden index on adverse health outcomes in Irish community-dwelling older people: a cohort study

BACKGROUND: The Drug Burden Index (DBI) quantifies exposure to medications with anticholinergic and/or sedative effects. A consensus list of DBI medications available in Ireland was recently developed for use as a DBI tool. The aim of this study was to validate this DBI tool by examining the association of DBI score with important health outcomes in Irish community-dwelling older people. METHODS: This was a cohort study using data from The Irish Longitudinal Study on Ageing (TILDA) with linked pharmacy claims data. Individuals aged ≥65 years participating in TILDA and enrolled in the General Medical Services scheme were eligible for inclusion. DBI score was determined by applying the DBI tool to participants’ medication dispensing data in the year prior to outcome assessment. DBI score was recoded into a categorical variable [none (0), low (> 0 and < 1), and high (≥1)]. Outcome measures included any Activities of Daily Living (ADL) impairment, any Instrumental Activities of Daily Living (IADL) impairment, any self-reported fall in the previous 12 months, any frailty criterion met (Fried Phenotype measure), quality of life (QoL) score (CASP-19 [Control Autonomy Self-realisation Pleasure] measure), and healthcare utilisation (any hospital admission and any emergency department (ED) visit) in the previous 12 months. Statistical analyses included multivariate logistic and linear regression models controlling for potential confounders. RESULTS: 61.3% (n = 1946) of participants received at least one DBI prescription in the year before their outcome assessment. High DBI exposure (DBI score ≥ 1) vs none was significantly associated with impaired function (ADL impairment adjusted OR 1.89, 95% CI 1.25, 2.88; IADL impairment adjusted OR 2.97, 95% CI 1.91, 4.61), self-reported falls (adjusted OR 1.50, 95%CI 1.03, 2.18), frailty (adjusted OR 1.74, 95% CI 1.14, 2.67), and reduced QoL (β = − 1.84, 95%CI -3.14, − 0.54). There was no significant association between DBI exposure and healthcare utilisation. CONCLUSIONS: The findings validate the use of the DBI tool for predicting risk of functional impairment, falls, frailty and reduced QoL in older people in Ireland, and may be extended to other European countries. Integration of this tool into routine practice may be an appropriate step forward to improve outcomes in older people.