Risk factors for mild cognitive impairment in Parkinson disease: a systematic review and meta-analysis

Mild cognitive impairment (MCI) is a common non-motor manifestation of Parkinson's disease (PD) and often precedes dementia. However, evidence on its demographic and clinical risk factors remains inconsistent. This study aimed to synthesize available data through a meta-analysis to identify determinants of MCI in PD.

This systematic review and meta-analysis followed PRISMA guidelines. Electronic databases were searched using MeSH terms and validated keywords. Studies were selected through a multi-step screening process by independent reviewers. Data extraction and quality assessment were performed using the Newcastle-Ottawa Scale. Meta-analyses were conducted using Comprehensive Meta-Analysis (v2). Random- or fixed-effects models were applied based on heterogeneity (I² threshold = 50%). Beggs and Mazumdar test assessed publication bias, with significance set at (P < 0.1).

This meta-analysis included 33 studies, Significant risk factors for MCI in individuals with PD included older age (effect size = 0.4, 95% CI: 0.315-0.498, P ≤ 0.001), older age at disease onset (effect size = 0.18, 95% CI: 0.05-0.327, P ≤ 0.001), and longer disease duration (effect size = 0.14, 95% CI: 0.08-0.2, P ≤ 0.001). Higher educational attainment showed a protective effect (effect size = -0.438, 95% CI: -0.555 to -0.321, P ≤ 0.001). No significant association was found between gender and MCI (OR = 0.899, 95% CI: 0.749-1.079, P = 0.253). Disease severity, based on UPDRS and Hoehn and Yahr scales, was significantly associated with increased MCI risk.

Advanced age, later disease onset, longer disease duration, and greater severity are key risk factors for MCI in PD. These findings highlight the need for early detection and proactive management to guide clinical decisions.