A short nap and natural bright light exposure improve positive mood status

National Institute of Occupational Safety and Health, Kanagawa, Japan.
Industrial Health (Impact Factor: 1.05). 04/2007; 45(2):301-8. DOI: 10.2486/indhealth.45.301
Source: PubMed

ABSTRACT While the effects of a short nap on performance and arousal level have been well investigated, less attention has been paid to its effects on mood status. The aim of the present study was to examine the effects of a short nap and natural bright light exposure on mood status. Participants were 16 healthy females who were on average 38.1 (SD = 2.68) yr old. From 11:00 to 12:00, the participants carried out a set of tasks twice with baseline lighting (<100 lux). From 12:40 to 13:10, they were subjected to three experimental conditions: control (<100 lux), natural bright light (>2,000 lux), and a 20-min nap. From 13:10 to 16:10, the tasks were repeated six times with the baseline lighting. To measure mood status, multiple visual analogue scales (to measure anxiety, sadness, anger, confusion, apathy, fatigue, and sleepiness) and the Mood Check List 3 (MCL-3) (to derive "pleasantness", "satisfaction" and "relaxation") were employed. The results showed that brief (30 min) natural bright light exposure improved one dimension of mood status, "pleasantness". A short nap also improved dimensions of mood status ("pleasantness", "satisfaction", and "relaxation"). These results suggest that the proper application of both natural light and a short nap shifts the mood status to the positive/favorable side.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Context: Neuroendocrine and immune stresses imposed by chronic sleep restriction are known to be involved in the harmful cardiovascular effects associated with poor sleep. Objectives: Despite a well-known beneficial effect of napping on alertness, its effects on neuroendocrine stress and immune responses after sleep restriction are largely unknown. Design: A strictly controlled (sleep-wake status, light environment, caloric intake), crossover, randomized design in continuously polysomnography-monitored subjects. Setting: The study was conducted in a laboratory-based study. Participants: The subjects were 11 healthy young men. Intervention: We investigated the effects on neuroendocrine and immune biomarkers of a night of sleep restricted to 2 h followed by a day without naps or with 30 minute morning and afternoon naps, both conditions followed by an ad libitum recovery night starting at 20:00. Main Outcome Measures: Salivary interleukin-6 and urinary catecholamines were assessed throughout the daytime study periods. Results: The increase in norepinephrine values seen at the end of the afternoon after the sleep-restricted night was not present when the subjects had the opportunity to take naps. Interleukin-6 changes observed after sleep deprivation were also normalized after napping. During the recovery day in the no-nap condition, there were increased levels of afternoon epinephrine and dopamine, which was not the case in the nap condition. A recovery night after napping was associated with a reduced amount of slow-wave sleep compared to after the no-nap condition. Conclusions: Our data suggest that napping has stress-releasing and immune effects. Napping could be easily applied in real settings as a countermeasure to the detrimental health consequences of sleep debt.
    Journal of Clinical Endocrinology &amp Metabolism 02/2015; 100(3):jc20142566. DOI:10.1210/jc.2014-2566 · 6.31 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Cognitive performance and alertness are two determinants for work efficiency, varying throughout the day and depending on bright light. We conducted a prospective crossover study evaluating the impacts of exposure to an intense, early morning illumination on sustained attention, alertness, mood, and serum melatonin levels in 33 healthy individuals. Compared with a dim illumination, the intense illumination negatively impacted performance requiring sustained attention; however, it positively impacted subjective alertness and mood and had no impact on serum melatonin levels. These results suggest that brief exposure to bright light in the morning hours can improve subjective measures of mood and alertness, but can also have detrimental effects on mental performance as a result of visual distraction. Therefore, it is important that adequate lighting should correspond to both non-visual and visual demands.
    Applied Ergonomics 08/2014; DOI:10.1016/j.apergo.2014.07.001 · 1.33 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Background: Studies examining acute exercise effects on energy and fatigue levels have not been quantitatively summarized. Purpose: To estimate the population effects of a single bout of exercise on energy and fatigue states and examine potential moderators. Methods: Google Scholar and MEDLINE were searched systematically for published studies that measured changes in energy and fatigue after acute exercise. Meta-analytic techniques were used to analyze 58 energy effects and 58 fatigue effects from the same 16 studies involving 678 participants. Most studies involved 21–40 minutes of moderate-intensity aerobic-type exercise. Result: The homogeneous mean effect for energy was Δ = 0.47 (95% confidence interval [CI] = 0.39, 0.56). The heterogeneous mean effect for fatigue was Δ = 0.03 (95% CI = −0.08, 0.13). The fatigue effect was moderated by a three-way interaction between change in feelings of energy, exercise intensity, and exercise duration. Conclusion: Acute exercise enhances feelings of energy. Decreases in fatigue occur only when post-exercise increases in energy are at least moderately large after low-to-moderate intensity exercise lasting longer than 20 minutes. Future research should focus on short-duration (40 minutes) exercise in non-student groups.
    10/2013; 1(4):223-242. DOI:10.1080/21641846.2013.843266


Available from