Inconsistent sleep was found to be significantly associated with inflammatory dysfunction, particularly in women, according to study findings published in Frontiers in Neurology.
Researchers note that poor sleep has been associated with higher levels of inflammatory biomarkers, in which higher average time awake, lower average time asleep, and lower sleep efficiency define poor sleep. Another factor, sleep inconsistency, has emerged as an important approach to quantifying sleep, with implications for physical and mental functioning.
Moreover, recent research suggests that sleep inconsistency, in addition to average sleep, may play an influential role in the development of these biomarkers. “Sleep inconsistency may represent an underlying collection of dysfunction in biological systems involved in sleep-wake regulation, dysfunction that may be missed by only examining average sleep,” explained the study authors.
“Biological mechanisms through which poor sleep adversely impacts health outcomes continue to be identified and include proinflammatory responses, the sympathetic nervous system, the renin-angiotensin-aldosterone system, and endothelial renal functioning,” they wrote
The study authors sought to further investigate this potential relationship between sleep and inflammation by examining sleep inconsistency and inflammatory biomarkers. The study conducted secondary analyses of the Survey of Midlife in the United States (MIDUS) sleep study, recruiting 533 individuals.
Participants completed nightly sleep diaries, actigraphy, and underwent a blood draw for the inflammatory biomarkers C-reactive protein, interleukin-6, and fibrinogen. Sleep inconsistency was derived from 7 consecutive nights of assessment and characterized as nightly fluctuations in several variables:
- terminal wakefulness
- number of awakenings
- time in bed
- sleep onset latency
- wake after sleep onset
Researchers utilized structural equation modeling to examine the influence of a latent average sleep variable and a latent sleep inconsistency variable on a latent inflammation variable. Models were adjusted for age, sex, body mass index, health, and medication, in which stratified models by sex were also analyzed.
In their assessments, researchers note that the average sleep model would not converge, in contrast with the sleep inconsistency model that was shown to fit the data well. Based on data analyses from the sleep inconsistency model, a significant positive association between the latent factors sleep inconsistency and inflammation was observed (β = 10.18; standard error (SE) = 4.40; P = .021), suggesting inconsistent sleep is associated with higher levels of inflammatory biomarkers.
After stratifying for sex, a significant association was observed between the latent sleep inconsistency factor and inflammation for women (β = 1.93; SE = 0.82; P = .018) but not men (β = 0.20; SE = 0.35; P = .566). Following multivariate adjustment, the association between sleep inconsistency and inflammation weakened (β = 6.23; SE = 3.71; P = .093).
“Inconsistent sleep may be an associated feature of inflammatory dysfunction, especially in women,” concluded the researchers. “Future studies should build upon this preliminary work and examine these associations longitudinally and through treatment trials.”
Dzierzewski JM, Donavan EK, Kay DB, Sannes TS, Bradbrook KE. Sleep inconsistency and markers of inflammation. Front Neurol. Published online September 16, 2020. doi:10.3389/fneur.2020.01042