Effect of Carbon Dioxide Exposure on the Daytime Sleepiness: A Bayesian Approach

概要

Carbon dioxide (CO2) is an odorless, tasteless, and colorless gas that affects humans' physiological conditions. Previous studies have reported that continuous CO2 exposure induced daytime sleepiness; however, the relationship between CO2 concentration and exposure time on daytime sleepiness induction was not fully understood. The present thesis aimed to elucidate the relationship between environmental CO2 concentration and daytime sleepiness. For this purpose, I examined daytime sleepiness development at 4,000 ppm of CO2 exposure. In the classical statistical analyses, no significant difference was found in the daytime sleepiness assessed by the Japanese version of the Karolinska Sleepiness Scale (KSS- J) scores between control (air) and CO2 conditions; however, strong evidence (BF10 = 6.681 x 107) of exposure time and weak evidence (BF10 = 0.448) between conditions were obtained when using the Bayesian statistical analyses. Further analysis by the Bayesian paired t-test revealed the largest difference of the KSS-J scores at a 40-min time point. In summary, the Bayesian statistical analyses showed anecdotal evidence that the exposure to 4,000 ppm of CO2 induced daytime sleepiness at 40-min.