Cognitive impairment in Parkinson’s disease: prevalence and associations with cardiometabolic, vascular, and autonomic factors—a systematic review and meta-analysis

Cognitive impairment is a common and disabling non-motor manifestation of Parkinson’s disease (PD), but its prevalence and associated factors remain unclear. This systematic review and meta-analysis aimed to estimate the pooled prevalence of cognitive impairment in PD and identify associated clinical factors. We searched electronic databases for observational studies and performed random-effects meta-analyses with subgroup analyses, sensitivity analyses, publication bias assessment, and GRADE evaluation. Fifty-five studies involving 103,145 participants were included. The pooled prevalence of cognitive impairment was 32.7% (95% CI: 27.1–38.7%), with substantial heterogeneity (I² = 97.7%). Prevalence varied according to diagnostic criteria and assessment tools. Orthostatic hypotension (OR = 2.18, 95% CI:1.71–2.77) and advanced age were strongly associated with cognitive impairment, while diabetes, hypertension, and metabolic syndrome showed additional associations. Evidence certainty ranged from low to very low. Cognitive impairment affects approximately one-third of individuals with PD, highlighting the need for early screening and longitudinal research.