The relationship between sleep apnoea and the risk of dementia: An updated systematic review and meta-analysis.

Introduction: To systematically analyse the relationship between sleep apnoea and the risk of dementia and assess the methodological quality of the most recent research evidence.

Material and methods: The PubMed, Embase and Cochrane Central Register of Controlled Trials databases were searched for relevant studies. We analysed hazard ratio (HR) or risk ratio values corresponding to random-effects models and their 95% confidence intervals (CI).

Results: We included 15 studies, which involved a total of 5,207,312 participants. Compared with individuals without sleep apnoea, those with sleep apnoea had a significantly increased risk of developing all-cause dementia, with an HR of 1.34 (95% CI: 1.17-1.53, p < 0.001, I 2 = 30%). Similarly, sleep apnoea significantly increased the risk of developing Alzheimer's disease and Parkinson's disease, with HRs of 1.28 (95% CI: 1.16-1.41, p < 0.001, I 2 = 22%) and 1.64 (95% CI: 1.47-1.82, p < 0.001, I 2 = 25%), respectively. However, the presence of sleep apnoea did not affect the incidence of vascular dementia, with an HR of 1.36 (95% CI: 0.88-2.10, p = 0.16, I 2 = 50%). Funnel plots showed an approximately symmetrical distribution for both types of data, suggesting no significant publication bias. In addition, sensitivity analyses on the overall results showed that there was still some heterogeneity among studies.

Conclusions: The common condition of sleep apnoea is significantly associated with the risk of developing dementia, particularly all-cause dementia, Alzheimer's disease and Parkinson's disease, but it does not significantly impact the risk of vascular dementia.