Objectives: Sleep, like many biological processes, is linked with immunity and inflammation such that "abnormal" sleep is associated with changes in circulating immune cells. These sleep patterns are also associated with increased mortality risk, and it may be that altered immune cell counts are one biological pathway through which sleep affects mortality. We used NHANES survey data to examine the associations between sleep duration, total white blood cell (WBC) count, and mortality from biological causes.
Methods: Several waves of public NHANES data (2005-2011; n = 11 353, ages 18+) were analyzed using bivariate statistics and causal mediation models including corrections for complex survey design.
Results: Deceased individuals were characterized by higher WBC but lower monocyte counts relative to surviving individuals. Significant associations between sleep duration, total WBC count, monocytes and mortality were found, as were marginally significant relationships between sleep and these cell counts. Significant mediated effects of sleep on mortality were found. Including covariates known to affect mortality, such as BMI, age, and self-reported health resulted in a nonsignificant mediated effect of sleep on mortality for monocytes, while mediated effects for total WBC count remained.
Conclusions: This large, cross-sectional analysis suggests that sleep duration is associated with changes in mortality risk through-in part-effects on leukocyte count. These findings support an immunological/inflammatory pathway linking sleep and mortality. Further research in populations with quantitatively different sleep patterns can determine whether this sleep-immune-mortality pathway is restricted to Western, industrial samples or is characteristic of humans in general.
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