No abstract

We investigated the effects of recreational exposure to the natural environment on mood and psychophysiological responses to stress. We hypothesized that walking in nature has restorative effects over and above the effects of exposure to nature scenes (viewing nature on TV) or physical exercise alone (walking on a treadmill in a gym) and that these effects are greater when participants were expected to be more stressed. Healthy university students ( N = 90) were randomly allocated to one of three conditions and tested during an exam-free period and again during their exam time. Mood and psychophysiological responses were assessed before and after the interventions, and again after a laboratory stressor. All interventions had restorative effects on cortisol levels ( p < .001), yet walking in nature resulted in lower cortisol levels than did nature viewing ( p < .05) during the exam period. Walking in nature improved mood more than watching nature scenes ( p < .001) or physical exercise alone ( p < .05).

SUMMARY Heart rate (HR) and heart rate variability (HRV) undergo marked fluctuations over the 24-h day. Although controversial, this 24-h rhythm is thought to be driven by the sleepwake/rest-activity cycle as well as by endogenous circadian rhythmicity. We quantified the endogenous circadian rhythm of HR and HRV and investigated whether this rhythm can be shifted by repeated melatonin administration while exposed to an altered photoperiod. Eight healthy males (age 24.4 ± 4.4 years) participated in a double-blind cross-over design study. In both conditions, volunteers were scheduled to 16 h-8 h rest : wake and dark : light cycles for nine consecutive days preceded and followed by 29-h constant routines (CR) for assessment of endogenous circadian rhythmicity. Melatonin (1.5 mg) or placebo was administered at the beginning of the extended sleep opportunities. For all polysomnographically verified wakefulness periods of the CR, we calculated the high-(HF) and low-(LF) frequency bands of the power spectrum of the R-R interval, the standard deviation of the normal-to-normal (NN) intervals (SDNN) and the square root of the mean-squared difference of successive NN intervals (rMSSD). HR and HRV variables revealed robust endogenous circadian rhythms with fitted maxima, respectively, in the afternoon (16:36 hours) and in the early morning (between 05:00 and 06:59 hours). Melatonin treatment phase-advanced HR, HF, SDNN and rMSSD, and these shifts were significantly greater than after placebo treatment. We conclude that endogenous circadian rhythmicity influences autonomic control of HR and that the timing of these endogenous rhythms can be altered by extended sleep/rest episodes and associated changes in photoperiod as well as by melatonin treatment.k e y w o r d s circadian, constant routine, heart rate, heart rate variability, light, melatonin, sleep

SUMMARY The aim of this study was to investigate sleep-related sweating as a symptom of obstructive sleep apnoea (OSA). Fifteen otherwise healthy male non-smoking patients with untreated moderate-to-severe OSA underwent polysomnography, including measurements of skin and core body temperature and electrodermal activity (EDA) as an objective indicator of sweating. Evening and morning blood pressure was measured as well as catecholamines in nocturnal urine. All measurements were repeated after 3 months on successful continuous positive airway pressure (CPAP) treatment. The untreated OSA subjects had a mean (±SD) apnoea-hypopnoea index of 45.3 ± 3.9 and a mean EDA index during sleep of 131.9 ± 22.4 events per hour. Patients with higher EDA indices had higher systolic blood pressure in the evening and morning (P = 0.001 and 0.006) and lower rapid eye movement (REM) sleep percentage (P = 0.003). The EDA index decreased significantly to 78.5 ± 17.7 in the patients on CPAP treatment (P = 0.04). The decrease correlated with lower evening systolic and diastolic blood pressure (P = 0.05 and 0.006) and an increase in REM% (P = 0.02). No relationship was observed between EDA and skin or core body temperature, or to catecholamine levels in urine. OSA patients who experience sleeprelated sweating may have increased blood pressure and decreased REM sleep compared with other OSA patients. CPAP treatment appears to lower blood pressure and increase REM sleep to a higher extent in these patients compared with other OSA patients.k e y w o r d s blood pressure, electrodermal activity, obstructive sleep apnoea, rapid eye movement, sweating, thermoregulation

A double-blind placebo-controlled study was carried out on 20 subjects to examine the early morning sedative effects of 2 g of L-tryptophan. Using brain mapping technique, 16-channel EEG recordings were topographically displayed. A distinct increase in theta amplitude, predominantly in the central region, together with an alpha reduction was observed after L-tryptophan administration, signs characterizing the EEG of drowsiness. Subjective self-rated sleepiness increased after the ingestion of L-tryptophan. Psychomotor performance, assessed by means of various psychometric tests, was not affected by this low dose of L-tryptophan.