Division of Biomedical Engineering for Health & Welfare, Tohoku University Graduate School of Biomedical Engineering, Sendai, Miyagi, Japan.
Department of Medicine and Science in Sports and Exercise, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan.
Indoor Air. 2022 Jun;32(6):e13055. doi: 10.1111/ina.13055.
Environmental carbon dioxide (CO ) could affect various mental and physiological activities in humans, but its effect on daytime sleepiness is still controversial. In a randomized and counterbalanced crossover study with twelve healthy volunteers, we applied a combinational approach using classical frequentist and Bayesian statistics to analyze the CO exposure effect on daytime sleepiness and electroencephalogram (EEG) signals. Subjective sleepiness was measured by the Japanese Karolinska Sleepiness Scale (KSS-J) by recording EEG during CO exposure at different concentrations: Normal (C), 4000 ppm (Moderately High: MH), and 40 000 ppm (high: H). The daytime sleepiness was significantly affected by the exposure time but not the CO condition in the classical statistics. On the other hand, the Bayesian paired t-test revealed that the CO exposure at the MH condition might induce daytime sleepiness at the 40-min point compared with the C condition. By contrast, EEG was significantly affected by a short exposure to the H condition but not exposure time. The Bayesian analysis of EEG was primarily consistent with results by the classical statistics but showed different credible levels in the Bayes' factor. Our result suggested that the EEG may not be suitable to detect objective sleepiness induced by CO exposure because the EEG signal was highly sensitive to environmental CO concentration. Our study would be helpful for researchers to revisit whether EEG is applicable as a judgment indicator of objective sleepiness.
环境二氧化碳（CO ）可能会影响人类的各种心理和生理活动，但它对日间嗜睡的影响仍存在争议。在一项有 12 名健康志愿者参与的随机、交叉对照研究中，我们采用了经典频率统计学和贝叶斯统计学相结合的方法，分析了 CO 暴露对日间嗜睡和脑电图（EEG）信号的影响。通过记录 CO 暴露在不同浓度下（正常：C、4000ppm（中度高：MH）和 40000ppm（高：H））时的 EEG，使用日本 Karolinska 嗜睡量表（KSS-J）来测量主观嗜睡程度。经典统计学显示，日间嗜睡受暴露时间影响，但不受 CO 条件影响。另一方面，贝叶斯配对 t 检验显示，与 C 条件相比，MH 条件下的 CO 暴露可能会在 40 分钟时引起日间嗜睡。相比之下，短时间暴露于 H 条件下会显著影响 EEG，但不会影响暴露时间。EEG 的贝叶斯分析主要与经典统计学的结果一致，但贝叶斯因子的可信度水平不同。我们的研究结果表明，由于 EEG 信号对环境 CO 浓度非常敏感，因此 EEG 可能不适合检测 CO 暴露引起的客观嗜睡。我们的研究将有助于研究人员重新考虑 EEG 是否可作为客观嗜睡的判断指标。
