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C-reactive protein Levels and Sleep Disturbances: Observations Based on The Northern Finland 1966 Birth Cohort Study

From the Department of Psychiatry (T.L), Savonlinna Central Hospital, Savonlinna, Finland; Department of Public Health Science and General Practice (T.L., J.J., M.T.), University of Oulu, Oulu, Finland; Department of Psychiatry (P.R.), University of Oulu, Oulu, Finland; Department of Psychiatry (P.R.), Oulu University Hospital, Oulu, Finland; Department of Clinical Chemistry (A.R.), University of Oulu, Oulu, Finland; Finnish Institute of Occupational Health (J.L.), Promotion of Work Ability and Health Team, Oulu, Finland; Unit of General Practice (J.J.), Oulu University Hospital, Oulu, Finland; National Public Health Institute (M.L.), Oulu, Finland; School of Engineering and Science (V.B.M.-R.), Jacobs University (formerly known as International University Bremen), Bremen, Germany; Department of Physiology (V.B.M.-R.), University of Oulu, Oulu, Finland.

Address correspondence and reprint requests to Timo Liukkonen, Department of Psychiatry, Savonlinna Central Hospital Keskussairaalantie 6, FIN-57120 Savonlinna, Finland. E-mail: liukkonen.timo{at}dnainternet.net

Objective: To investigate whether sleep disturbances are associated with C-reactive protein (CRP) levels at the population level. Elevated CRP levels have been found to accompany sleep disturbances, but evidence so far comes only from limited clinical and experimental studies; epidemiological studies are lacking.

Methods: We utilized the Northern Finland 1966 Birth Cohort, whose participants have been followed up to the age of 31 years. The hs-enzyme immunoassay method was used to measure highly sensitive-CRP (hs-CRP) concentrations (4011 participants). Self-reported sleep disturbances were ranked from 1 (no problem) to 5 (severe disturbances).

Results: Multivariate analyses, after adjusting for confounders, revealed that hs-CRP levels in men in the sleep disturbance category "moderate, considerable and severe" (i.e., self-reported sleep disturbances rated 3, 4, or 5), were >18% (18.2%, 95% Confidence Interval 3.0% to 36.3%) higher than those in men with "no" sleep disturbance. In women, hs-CRP levels did not significantly differ between different sleep disturbance categories.

Conclusions: Our results support the hypothesis that moderate-to-severe sleep disturbances in men are associated with slightly increased CRP levels at the epidemiological level. Further investigations are called for to see whether our results can be replicated in other databases.

Key Words: C-reactive protein • inflammation • sleep • sleep disturbances

Abbreviations: CRP = C-reactive protein; IL-6 = interleukin-6; EIA = enzyme immunoassay; Hs-CRP = highly sensitive C-reactive protein; HSCL-25 = Hopkins Symptom Checklist-25.