Differential effects of physical activity and sleep duration on cognitive function in young adults

Purpose: Although exercise and sleep duration habits are associated with cognitive function, their beneficial effects on cognitive function remain unclear. We aimed to examine the effect of sleep duration and daily physical activity on cognitive function, elucidating the neural mechanisms using near-infrared spectroscopy(NIRS).Methods: A total of 23 healthy young adults(age 22.0 ± 2.2 years) participated in this study. Exercise amount was assessed using a uniaxial accelerometer. We evaluated total sleep time(TST) and sleep efficiency by actigraphy. Cognitive function was tested using the N-back task, the Wisconsin Card Sorting Test(WCST), and the Continuous Performance Test—Identical Pairs(CPT-IP), and the cortical oxygenated hemoglobin levels during a word fluency task were measured with NIRS.Results: Exercise amount was significantly correlated with reaction time on 0- and 1-back tasks(r = —0.602, p = 0.002; r = —0.446, p = 0.033,respectively), whereas TST was significantly correlated with % corrects on the 2-back task(r = 0.486, p = 0.019). Multiple regression analysis,including exercise amount, TST, and sleep efficiency, revealed that exercise amount was the most significant factor for reaction time on 0- and 1-back tasks(b = —0.634, p = 0.002; b = —0.454, p = 0.031, respectively), and TST was the most significant factor for % corrects on the 2-back task(b = 0.542, p = 0.014). The parameter measured by WCST and CPT-IP was not significantly correlated with TST or exercise amount. Exercise amount, but not TST, was significantly correlated with the mean area under the NIRS curve in the prefrontal area(r = 0.492, p = 0.017).Conclusion: Exercise amount and TST had differential effects on working memory and cortical activation in the prefrontal area. Daily physical activity and appropriate sleep duration may play an important role in working memory.

Sleep Fragmentation and Risk of Automobile Accidents in Patients with Obstructive Sleep Apnea—Sleep Fragmentation and Automobile Accidents in OSA

Objectives: Automobile accidents related to obstructive sleep apnea (OSA) represent an important public health concern. Frequent arousal response during sleep is responsible for the symptoms of daytime sleepiness and an increased risk of automobile accidents in patients with OSA. We therefore investigated the potential relationships between the intensity of arousal and occurrence of automobile accidents in OSA. Methods: We determined the incidence of automobile accidents in the past 5 years among 51 men with OSA (age, 58.5 ± 10.4 years) using a questionnaire. Daytime sleepiness was rated with the Epworth Sleepiness Scale (ESS). We calculated an automobile accident score, with two points per automobile accident causing damage and one point per near miss. Standard polysomnography was performed for all patients, and arousals were classified as electroencephalographic (EEG) arousal of an abrupt shift in EEG frequency alone and Movement arousal, which was defined as EEG arousal with increased electromyographic activity persisting for ≥3 s. The number of EEG or Movement arousals per hour (arousal index) was determined. Results: The Movement arousal index was significantly greater in the 27 patients who experienced at least one automobile accident causing damage than in the resting 24 patients who had no history of automobile accidents. Multiple regression analysis including age, body mass index, and sleep parameters revealed that the Movement arousal index was the most significant factor of risk for automobile accidents (β = 0.563, P = 0.017) as well as the ESS score (β = 0.417, P = 0.022). Conclusion: Movement arousal during sleep contributes to daytime sleepiness and the resulting frequent involvement of OSA patients in automobile accidents.