Intraindividual Variability in Sleep and Levels of Systemic Inflammation in Nurses

Abstract

Objective: Disturbed sleep is common among nurses and is associated with morbidity and mortality. Inflammation may be one mechanism linking sleep and disease. Yet most studies have relied on retrospective questionnaires to assess sleep, which fail to account for night-to-night fluctuations in sleep across time (i.e., intraindividual variability (IIV]). We examined prospective associations between mean and IIV in sleep with inflammation markers in nurses.

Methods: Participants were 392 nurses (Mage = 39.54, 92% female; 23% night-shift working) who completed 7 days of sleep diaries and actigraphy to assess mean and IIV in total sleep time (TST) and sleep efficiency (SE). Blood was drawn on day 7 to assess inflammation markers C-reactive protein (CRP), interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), and interleukin-1 beta (IL-1β).

Results: Greater intraindividual variability in TST — measured via both actigraphy and sleep diary — was associated with higher IL-6 (actigraphy β = 0.05, p = .046, sr2 = .01; diary β = 0.04, p = .030, sr2 = .01) and IL-1β (actigraphy β = 0.12, p = .008, sr2 = .02; diary β = 0.09, p = .025, sr2 = .01), but not CRP or TNF-α. IIV in actigraphy- and sleep diary-determined SE was not associated with inflammation biomarkers, nor were any mean sleep variables. Shift work did not moderate any associations.

Conclusions: Nurses with more variable sleep durations had elevated levels of inflammation, which may increase risk for development of inflammatory-related diseases. Research should investigate how sleep regularization may change levels of inflammation and improve health.