Consequences of polypharmacy among the people living with dementia: a systematic review and meta-analysis

Background The objective of this systematic review and meta-analysis was to synthesise and summarise studies on the consequences of polypharmacy on people living with dementia (PwD), categorize the consequences, analyse the quality of the studies, and estimate pooled effect sizes of these consequences. Methods A systematic literature review was conducted following the PRISMA guideline. Covidence software was used for screening, study selection and data extraction. The quality of the selected studies was assessed using an adapted version of Newcastle-Ottawa Scale (NOS) scale. Random effect models were used to perform the meta-analyses and the heterogeneity among the studies was assessed by i 2 statistics. Results Nineteen studies were selected for this review. The four most frequent consequences were: potentially inappropriate medication (PIM) (n = 6, 31.6%), hospitalisation (n = 4, 21%), adverse drug reaction (ADR) (n = 3, 15.8%), and mortality (n = 3, 15.8%), all of which were significantly associated with polypharmacy. The quality of the reviewed studies was fair to good quality (good, n = 13 and fair, n = 6). Meta-analysis was performed with five studies related to PIM and revealed that the odds of having PIM among the PwD exposed to polypharmacy was 2.93 times (95% CI: 2.24–3.82; I2 = 95.6%). Heterogeneity was observed in the selected studies with regards to study design, sample size, follow-up duration, adjustment of confounders, as well as definitions of polypharmacy and inconsistent tools for dementia diagnosis. Conclusions Polypharmacy is associated with PIM use, ADR, mortality and hospitalisation for PwD despite high heterogeneity among the studies in terms of polypharmacy definition and dementia diagnosis.