The association between sleep duration and cognitive function in the US elderly from NHANES 2011-2014: A mediation analysis for inflammatory biomarkers

Background: Studies have shown a close association between sleep duration and cognitive function in older adults. However, no studies have explored the underlying mechanisms of this relationship. This study was designed to assess the role of inflammatory markers in the relationship between sleep duration and cognitive function in older Americans. Methods: A total of 2502 participants from the National Health and Nutrition Examination Survey (NHANES) were included in the analysis. Cognitive function was assessed using three tests from NHANES. Sleep duration was evaluated through a self-reported sleep time questionnaire. Inflammatory biomarkers examined included leukocytes (WBC) count, neutrophil count (NE), the neutrophil-to-lymphocyte ratio (NLR), and the systemic immune-inflammation index (SII). Mediation models were constructed to clarify the mediating role of inflammatory biomarkers. Results: Long sleep duration (>= 9 h) was associated with lower performance on CERAD (OR:-1.623; 95 % CI:-2.979 to-0.267) and DSST (OR:-3.084; 95 % CI:-5.861 to-0.308) compared to the normal sleep duration group (7-9 h). NE partially and indirectly mediated this association. Meanwhile, WBC moderated the association between long sleep duration (>= 9 h) and DSST performance. Limitations: The cross-sectional design prevents making causal inferences. Conclusions: Long sleep duration is a risk factor for cognitive function. Inflammatory biomarkers based on blood cells present a readily accessible and cost-effective strategy for identifying sleep disorders and also significantly mediate the association between long sleep duration and cognitive function.