C-reactive protein levels and sleep disturbances: observations based on the Northern Finland 1966 Birth Cohort study.

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.