Long-term exposure to residential traffic noise and changes in body weight and waist circumference: A cohort study.

BACKGROUND: Traffic noise can act as a stressor and disturb sleep, and has been associated with cardiovascular disease. Recent studies suggest a possible association to metabolic outcomes and adiposity through biological mechanisms related to physiological stress and sleep disturbance. OBJECTIVES: We aimed to investigate the association between long-term residential traffic noise and changes in adiposity. MATERIALS AND METHODS: The study was based on 39,720 middle-aged Danish men and women from a cohort, with information on weight and waist circumference at two points in time. Residential exposure to traffic noise was calculated for all participants' present and historical addresses using the Nordic prediction method. The associations between traffic noise and changes in adiposity measures after a mean follow-up of 5.3 years were analyzed by linear and logistic regression with adjustments for age, sex, socioeconomic position and lifestyle factors in three models with increasing adjustment. RESULTS: In linear models adjusted for sex, age, socioeconomic position and competing noise sources we found road traffic noise to be significantly associated with small gains in both weight and waist circumference. For example, time-weighted mean exposure 5-years preceding follow-up was associated with a yearly weight gain of 15.4 g (95% confidence interval (CI): 2.14; 28.7) and a yearly increase in waist circumference of 0.22 mm (95% CI: 0.018; 0.43) per 10dB. Similarly, in Poisson regression models we found an 10% increased risk for gaining more than 5 kg body weight during follow-up (95% CI: 1.04; 1.15) per 10 dB higher 5 years exposure preceding follow-up. Exposure to railway noise above 55 dB was associated with weight gain (39.9 g/year (95% CI: 10.2; 69.6)), but not with a significant change in waist circumference. We found baseline BMI (p<0.001) and waist circumference (p=0.001) to be significant effect modifiers for the association between road traffic noise and waist circumference, with gain in waist circumference only among the obese (BMI≥30) participants (1.20 mm/year (95% CI: 0.68; 1.72)) and participants with a large waist circumference (0.83 mm/year (95% CI: 0.42; 1.23)). CONCLUSION: The findings supports previous studies suggesting that traffic noise may be associated with development of adiposity. However, the potential effects are small and suggest an effect mainly among obese participants.

Effects of artificial dawn and morning blue light on daytime cognitive performance, well-being, cortisol and melatonin levels.

Light exposure elicits numerous effects on human physiology and behavior, such as better cognitive performance and mood. Here we investigated the role of morning light exposure as a countermeasure for impaired cognitive performance and mood under sleep restriction (SR). Seventeen participants took part of a 48h laboratory protocol, during which three different light settings (separated by 2 wks) were administered each morning after two 6-h sleep restriction nights: a blue monochromatic LED (light-emitting diode) light condition (BL; 100 lux at 470 nm for 20 min) starting 2 h after scheduled wake-up time, a dawn-simulating light (DsL) starting 30 min before and ending 20 min after scheduled wake-up time (polychromatic light gradually increasing from 0 to 250 lux), and a dim light (DL) condition for 2 h beginning upon scheduled wake time (<8 lux). Cognitive tasks were performed every 2 h during scheduled wakefulness, and questionnaires were administered hourly to assess subjective sleepiness, mood, and well-being. Salivary melatonin and cortisol were collected throughout scheduled wakefulness in regular intervals, and the effects on melatonin were measured after only one light pulse. Following the first SR, analysis of the time course of cognitive performance during scheduled wakefulness indicated a decrease following DL, whereas it remained stable following BL and significantly improved after DsL. Cognitive performance levels during the second day after SR were not significantly affected by the different light conditions. However, after both SR nights, mood and well-being were significantly enhanced after exposure to morning DsL compared with DL and BL. Melatonin onset occurred earlier after morning BL exposure, than after morning DsL and DL, whereas salivary cortisol levels were higher at wake-up time after DsL compared with BL and DL. Our data indicate that exposure to an artificial morning dawn simulation light improves subjective well-being, mood, and cognitive performance, as compared with DL and BL, with minimal impact on circadian phase. Thus, DsL may provide an effective strategy for enhancing cognitive performance, well-being, and mood under mild sleep restriction.

Sex-specific associations between sleep problems and hypothalamic-pituitary-adrenocortical axis activity in children.

STUDY OBJECTIVES: Sleep problems are associated with reduced physical and mental health. Altered function of the hypothalamic-pituitary-adrenocortical axis (HPAA) may be one underlying mechanism. We studied the associations between sleep problems and HPAA activity in children. DESIGN: A cross-sectional epidemiological cohort study. SETTING: Salivary cortisol was sampled throughout one day at home and during the Trier Social Stress Test for Children (TSST-C) in clinic. Sleep disorders were measured with a parent-rated Sleep Disturbance Scale for Children, and sleep duration measured by actigraphy for one week. PARTICIPANTS: 284 (51% girls) 8-year-old children. RESULTS: Boys with sleep problems (≥ 85 th percentile in any of the sleep-wake transition, arousal, excessive daytime somnolence or sleep hyperhydrosis subscales) had lower diurnal salivary cortisol levels and salivary cortisol responses to TSST-C stress in comparison to boys without sleep problems. Girls with sleep problems (≥ 85 th percentile in disorders of initiating and maintaining sleep) displayed a higher overall level of salivary cortisol during the TSST-C. Salivary cortisol responses to stress were lower in boys and higher in girls with more than one sleep problem. CONCLUSIONS: Sleep problems in children are associated with altered HPAA function, after controlling for actual sleep quantity measured by actigraphy. Boys with sleep problems had lower HPAA activity and girls with sleep problems had higher HPAA activity, compared to children without sleep problems.

Stress and fatigue in sound engineers: the effect of broadcasting in a life show and shift work.

The aim was to study the time-of-day variations of cortisol, fatigue and sleep disturbances in sound engineers in relation to job task and shift work. The concentration of saliva cortisol and feeling of stress, sleepiness and fatigue were followed at three hour intervals in 21 sound engineers: 13 sound engineers, aged 45.1 +/- 7.3 years, broadcasting in a life show during fast forward rotating shifts and 8 sound engineers, aged 47.1 +/- 9.8 years, making records in a studio during fast rotating day shifts. Cortisol concentration was assessed in saliva with radioimmunological kits. The participants reported for stress symptoms during the shifts and filled sleep diary. The data were analyzed by tests of between-subjects effects (SPSS). A trend for higher cortisol was found with the group broadcasting in a life show. The sound engineers broadcasting in a life show reported higher scores of stress, sleepiness and fatigue, but no significant differences concerning the sleep disturbances between the groups were found. In conclusion our data show moderate level of stress and fatigue with the studied sound engineers, higher with the subjects broadcasting in a life show. The quality of sleep showed no significant differences between the studied groups, an indication that the sound engineers were able to tolerate the fast forward rotating shifts.

Variations of cortisol, fatigue and sleep disturbances in sound engineers: effect of job task and fast backward-rotating shifts.

The aim was to study the effect of job task and fast backward-rotating shifts on the time-of-day variations of cortisol, fatigue, and sleep disturbances in broadcasting sound engineers. The concentration of saliva cortisol and ratings of stress, sleepiness, and fatigue were followed at 3-hour intervals during the fast backward-rotating shifts in 26 sound engineers: 14 subjects from control rooms, aged 45.1 +/- 7.3 years, and 12 subjects working in direct transmissions, aged 51.7 +/- 6.0 years. Saliva cortisol was assessed using an radioimmunology kit. The participants reported for stress symptoms after the shifts and filled a sleep diary. The effects of job task, shift, and time-of-day were analyzed by tests of between-subjects effects (SPSS). Cortisol retained the typical diurnal pattern with a highly significant effect of the shift. The job task and the shift interacted significantly. Higher cortisol values during the morning and night shifts in engineers working in direct transmissions were found. Their stress ratings were also higher, as well as the ratings of sleepiness and fatigue. The quality of sleep was worse in engineers working in direct transmissions. In conclusion, our data indicate that stress and fast backward-rotating shifts in sound engineers working in direct transmissions affect physiological stress markers such as cortisol and increase sleepiness, fatigue, and sleep problems.