Artificial light at night (ALAN) has become a ubiquitous part of our society. Animal studies have shown that ALAN exposure promotes a depressive-like mood and increases peripheral inflammation likely due to circadian disruption. We hypothesized that sleeping with ALAN will increase systemic inflammation in humans.
We enrolled 64 subjects [32 with obstructive sleep apnea (OSA) adherent to treatment and 32 without sleep disorders] in a randomized, crossover study to determine the effects of sleeping with ALAN (40 lux) or the usual dark condition (control) for 7 nights at home. Sleeping with ALAN was confirmed by an actigraph with an ambient light sensor. Outcome measurements were done at baseline and after sleeping in each condition. The primary outcome was changes in the high-sensitivity C-reactive protein (hsCRP) levels. Secondary outcomes include scores on the Pittsburgh Sleep Quality Index (PSQI), Center for Epidemiologic Studies Depression Scale (CES-D), Functional Outcomes of Sleep Questionnaire-10 (FOSQ-10), and Epworth Sleepiness Scale (ESS); Psychomotor Vigilance Testing (PVT); actigraphic sleep measures; and homeostatic model assessment of insulin resistance (HOMA-IR). A random effects linear regression model was used to assess differences adjusting for schedule, visit, and baseline levels. Post-hoc analyses combined results from OSA and non-OSA subjects.
Fifty-eight (30 OSA and 28 non-OSA) subjects, aged 38.4±14.9 years, 33 of whom are male completed the protocol. A log transformation was used so the difference in hsCRP was expressed as a mean ratio. In the combined analysis, the mean hsCRP was 39% higher with ALAN than control (mean ratio=1.39; 95% CI: 1.08-1.80; p=0.012). The effects of ALAN for OSA and non-OSA subjects were not different. ALAN increased the CES-D score by 1.81 (p=0.017) and ESS score by 0.62 (p=0.071) points, and decreased the FOSQ-10 score by 0.36 (p=0.038) points while the PSQI score was unchanged (p=0.860). There were no significant differences in the PVT values, actigraphic sleep measures, or HOMA-IR.
Sleeping with ALAN for seven days significantly increased hsCRP levels and modestly increased depression scores in humans.