Background: Polypharmacy is a prevalent condition in older adults, especially those with multiple chronic diseases, and has been largely associated with adverse outcomes, including disability, hospitalizations, and death.

Aims: This systematic review focused on diabetes and aimed to investigate the prevalence and impact of polypharmacy in older adults affected by such disease.

Methods: Observational (either cross-sectional or longitudinal) or experimental studies investigating the frequency and impact of polypharmacy in older adults with diabetes were identified from scientific databases and grey literature until August 2021. The prevalence and the 95% Confidence Interval (95% CI) of polypharmacy in older people with diabetes were summarized by a random-effects meta-analysis.

Results: From a total of 1465 records, 9 were selected for the qualitative synthesis, and 8 for the quantitative synthesis. Most studies defined polypharmacy using a cut-off for the minimum number of medications ranging from 4 to 6 drugs/day. The pooled prevalence of polypharmacy in older people with diabetes was 64% (95% CI 45-80%). Considering studies that used the same definition of polypharmacy (i.e. ≥ 5 drugs/day), the pooled prevalence was 50% (95% CI 37-63%). The between-studies heterogeneity was high. Across the selected studies, polypharmacy seemed to negatively influence both diabetes-specific (poor glycemic control and risk of hypoglycemia) and health-related (risk of incident falls, syncope, hospitalization, and death) outcomes.

Conclusion: This systematic review confirms the high prevalence of polypharmacy in older people with diabetes and its strong impact on several health-related outcomes, including mortality. These results strengthen the need to improve care strategies for management of these patients.