Joint association of daytime sleep behaviors and dietary quality with the risk of dementia: A large prospective cohort study

Background Identifying modifiable risk factors of dementia is crucial for its early prevention. Daytime sleep behaviors (DSB) and diet are synergetic factors, both potentially important in maintaining cognitive health. However, whether they may jointly influence the risk of dementia in the general population remains unclear. Methods This study included 187,078 participants from the UK Biobank. DSB burden (low, medium, and high) was assessed through two questions regarding daytime sleepiness and napping. The Recommended Food Score (RFS) was calculated to assess dietary quality (by tertile). We ascertained incident dementia through linkage to hospital inpatient records. We used Cox proportional hazards regression models to estimate the associations. Results During a median follow-up of 10 years, we documented 1,351 cases with incident dementia. Compared with participants with low DSB burden, those with high DSB burden had a 21% (hazard ratio [HR]: 1.21; 95% confidence interval [CI]: 1.06, 1.38) higher risk of incident dementia. Dietary quality was negatively associated with dementia risk (HR for tertile 1 versus tertile 3: 1.42; 95% CI: 1.24, 1.63). There was a significant interaction between DSB burden and RFS (P for interaction = 0.027). Compared with participants with low DSB burden & high RFS, those with high DSB burden had higher risks of incident dementia, regardless of RFS level. Conclusions High DSB burden and low dietary quality separately or in joint were significantly associated with higher risks of incident dementia, while high DSB burden seems to play a decisive role. Our findings imply that programs targeting the two behavioral factors, particularly the DSB, may help to prevent dementia. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This research was supported by funding from Damian Health Tech (Hangzhou) CO., LTD (Kheng-20220141, ZL), the Natural Science Foundation of Zhejiang Province (LQ21H260003), the National Natural Science Foundation of China (82171584), the 2020 Milstein Medical Asian American Partnership Foundation Irma and Paul Milstein Program for Senior Health project award (ZL), and funding from Key Laboratory of Intelligent Preventive Medicine of Zhejiang Province (2020E10004), and Zhejiang University Global Partnership Fund (188170-11103). The funders had no role in the design of the study and collection, analysis, and interpretation of data and in writing the manuscript. Views expressed in this study are solely those of the authors and do not necessarily reflect those of Zhejiang University. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: https://www.ukbiobank.ac.uk/enable-your-research/register I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes The datasets supporting the conclusions of this article are available at www.ukbiobank.ac.uk/register-apply.