Associations between slow-wave sleep and dementia: a systematic review.

Objective: To conduct a systematic review of the literature to examine the associations between slowwave sleep (SWS) disturbance and dementia.

Methods: We systematically searched PubMed and Embase for cohort and case-control studies that examined SWS differences between patients with dementia and healthy controls. Study quality was assessed using the Newcastle-Ottawa Scale.

Results: In total, 19 studies (three cohort and 16 case-control) were included in analysis. Overall, one cohort study and 14 case-control studies found that reduced SWS was associated with dementia; the evidence was stronger in case-control studies than cohort studies. Study quality of studies varied; most were above average.

Conclusion: Most studies regarding the association between SWS and dementia are cross-sectional; more longitudinal studies are needed to determine whether reduction in SWS can predict incident dementia. Future studies should include multi-night recordings and the use of standardised criteria to enhance the accuracy of recordings and facilitate comparisons between studies.