Effect of polypharmacy, potentially inappropriate medications and anticholinergic burden on clinical outcomes: A retrospective cohort study

Background: Polypharmacy, potentially inappropriate medications and anticholinergic burden (as assessed by the anticholinergic risk scale) are commonly used as quality indicators of pharma-cotherapy in older adults. However, their role in clinical practice is undefined. We sought to investigate longitudinal changes in these indicators and their effects on clinical outcomes. Methods: We used Taiwan's Longitudinal Health Insurance Database to retrieve quarterly information about drug use for people aged 65 years and older over a 10-year period. We analyzed the association between indicators and all-cause admission to hospital, fracture-specific admission to hospital and death using generalized estimating equations. Results: The study cohort comprised 59 042 older adults (65-74 yr: 39 358 [66.7%], 75-84 yr: 16 903 [28.6%], and ≥ 85 yr: 2781 [4.7%]). The mean changes in polypharmacy over the course of the study were greatest among patients aged 65-74 years (absolute difference +2.14, 95% confidence interval [CI] 2.10-2.19), then among those aged 75-84 yr (+1.79, 95% CI 1.70-1.88), and finally those aged 85 years and older (+0.71, 95% CI 0.36-1.05). The number of potentially inappropriate medications increased among patients aged 65-74 years (+0.16 [0.15-0.18]) and 75-84 years (+0.09 [0.06-0.08]), but decreased in those aged 85 years and older (-0.15 [-0.26 to-0.04]). Polypharmacy, potentially inappropriate medications and anticholinergic risk scale were each associated with an increased risk of admission to hospital, but not with death. In addition, both polypharmacy (5-9 drugs: odds ratio [OR] 1.18, 95% CI 1.12-1.24; ≥ 10 drugs: OR 1.54, 95% CI 1.42-1.66) and anticholinergic burden (score 1-2: 1.39, 95% CI 1.31-1.48; ≥ 3: 1.53, 95% CI 1.41-1.66) showed dose-response relations with fracture-specific admission to hospital. Interpretation: The total number of drugs taken (polypharmacy), number of potentially inappropriate medications and anticholinergic risk changed during follow-up and varied across age groups in this cohort of older adult patients. These indicators showed dose-response relations with admission to hospital, but not with death.