Active smoking, sleep quality and cerebrospinal fluid biomarkers of neuroinflammation.

Backgrounds: Cigarette smoking has been shown to be associated with sleep disorders and the related neuropathogenesis including neuroinflammation. Previous studies showed that pro- and anti-inflammatory cytokines are physiologically important in maintaining circadian function. In addition, sleep deprivation leads to immune dysregulations. However, no study has been published yet by using cerebrospinal fluid (CSF) biomarkers of neuroinflammation to investigate the relationship between active cigarette smoking and sleep disorders.

Methods: CSF tissues from subjects of 191 male subjects (non-smokers n = 104; active smokers n = 87) receiving local anesthesia before surgery for anterior cruciate ligament injuries were obtained after the assessment of clinical information and Pittsburgh Sleep Quality Index (PSQI). The levels of tumor necrosis factor alpha (TNFα), Interleukin (IL) 1 beta (IL1β), IL2, IL4, IL6 and IL10 were measured using radioimmunoassay and ELISA.

Results: PSQI scores were significantly higher in active smokers than that in non-smokers (p < 0.001, Cohen's d = 0.63). Significantly higher levels of CSF TNFα were found in active smokers compared to non-smokers (28 ± 1.97 vs. 22.97 ± 2.48, p < 0.05, Cohen's d = 2.23). There was a positive correlation between CSF IL1β levels and PSQI scores in non-smokers (r = 0.31, p = 0.01, adjustment R-Squared = 0.11).

Discussion: This is the first study to reveal the association between higher CSF TNFα levels and poorer sleep quality in active smoking. In addition, CSF IL1β levels might be a potential biomarker in central nervous system for circadian dysregulation.