Abstract
Systemic inflammation is thought to mediate the link between sleep and cardiovascular outcomes, but previous studies on sleep habits and inflammation markers have found inconsistent results. This study investigated the relationship between sleep characteristics and C-reactive protein (CRP), interleukin-6 (IL-6) and tumor necrosis factor α (TNFα). A representative sample of 319 Swedish women was randomly selected from the general population for in-home polysomnography, sleep questionnaire and blood samples. As variables were highly correlated, principal component analysis was used to reduce the number of original variables. Linear regression with log-transformation of the outcomes (lnCRP, lnIL-6 and lnTNFα) and quantile regression were fitted to estimate cross-sectional relationships. Multivariable linear regression models suggested a significant association of insomnia symptoms (self-reported) with higher lnCRP levels (β=0.11; 95% confidence interval [CI]=0.02; 0.21), but not with lnIL-6 and lnTNFα. From quantile regression analysis we found that a high non-restorative index (subjective) and insomnia symptoms (self-reported) were associated with higher values of CRP, especially in the highest quantiles of the CRP distribution (90th percentile: β=0.71; 95% CI=0.17; 1.24. β=1.23; 95% CI=0.44; 2.02, respectively). Additionally, higher amounts of rapid eye movement (REM) sleep were associated with lower CRP values (90th percentile: β=-0.80; 95% CI=-0.14; -1.46). In conclusion, sleep disturbances (self-reported), specifically difficulties maintaining sleep and early morning awakenings, but not sleep duration (neither subjective nor objective), were associated with higher CRP levels. No association was found with IL-6 or TNFα. Elevated REM sleep was associated with lower CRP levels. The results suggest that inflammation might be an intermediate mechanism linking sleep and health in women.
Highlights
Humans spend around one-third of their lives sleeping, and sleep has long been acknowledged as an essential component of human health (Grandner, 2017)
Results from linear regression models adjusted for age, BMI and waist circumference suggested a significant association of insomnia symptoms (PC2(s)) with higher C-reactive protein (CRP) levels, but not with IL-6 and tumor necrosis factor α (TNFα)
The average CRP levels in women with early morning awakenings were 72% higher compared to women without such complaints (β = 0.54 [exp(β) = 1.72]; 95% CI = 0.22; 0.87), whereas no association was observed between difficulties initiating sleep and CRP levels (β = −0.41; 95% CI = −0.83; 0.01)
Summary
Humans spend around one-third of their lives sleeping, and sleep has long been acknowledged as an essential component of human health (Grandner, 2017). Large epidemiological studies have found increases in C-reactive protein (CRP) levels in men with extreme (short and/or long) self-reported sleep durations, but not in women (Grandner, Buxton, et al, 2013; Richardson & Churilla, 2017). Short sleep duration was not found to be associated with inflammation markers, either in the observational or in the experimental studies, whereas long sleep duration was associated with increases in CRP and IL-6 levels (Irwin et al, 2016). Many studies included in this meta-analysis, did not report adjusted estimates and the majority of them used sleep questionnaires instead of objective measures such as polysomnography (PSG). The aim of the present study was to investigate the role of sleep (assessed with both questionnaires and polysomnography) in markers of inflammation (CRP, IL-6 and TNFα), using a sample of 319 Swedish women from the general population. Given the modifiable nature of sleep behaviour, gaining new insights into its association with inflammatory markers might have important public health implications
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
