Risk factors for rapid eye-movement sleep-related behavioral disorders (RBDs): A systematic review and a meta-analysis

The present study aimed to systematically analyze the risk factors for RBD.A systematic review and meta-analysis of case-control studies, cohort studies, and cross-sectional studies derived from the articles published in eight electronic databases before December 1, 2021. The primary outcome was the odds ratio (OR) and 95% confidence interval (95% CI), and heterogeneity was quantified using I2. Subgroup analyses and meta-regression were used to explore sources of heterogeneity. Egger's test and sensitivity analysis were performed. The PROSPERO ID number of the present study is CRD42021293942.We identified 26 studies (44,230 subjects) among 2022 citations, and 13 factors were considered. Male sex (OR = 1.36, 95% CI = 1.13-1.64), smoking (OR = 1.37, 95% CI: 1.26-1.50), depression (OR = 2.06, 95% CI = 1.66-2.56), antidepressant use (OR = 2.36, 95% CI = 1.98-2.82), duration of neuropsychiatric disorders(OR = 1.43, 95% CI = 1.13-1.73), levodopa equivalent daily dose (LEDD, OR = 60.15, 95% CI = 23.95-96.35) and observable motor dysfunction (OR = 2.43, 95% CI = 0.65-4.22) were associated with a higher risk of RBD. Tertiary education and above (OR = 0.58, 95% CI = 0.35-0.96) was associated with a lower RBD risk. Men (OR = 1.40, 95% CI: 1.10-1.78, I2 = 0%, P = 0.005) and older individual (OR = 2.73, 95% CI: 1.03-4.43, I2 = 60%, P = 0.002) were more likely to have iRBD.Six modifiable risk factors and one protective factor were associated with RBD. Further research is required to understand the mechanisms and to develop preventative strategies.