Effect of exposure to evening light on sleep initiation in the elderly: A longitudinal analysis for repeated measurements in home settings

Abstract

Epidemiologic data have demonstrated associations of sleep-onset insomnia with a variety of diseases, including depression, dementia, diabetes and cardiovascular diseases. Sleep initiation is controlled by the suprachiasmatic nucleus of the hypothalamus and endogenous melatonin, both of which are influenced by environmental light. Exposure to evening light is hypothesized to cause circadian phase delay and melatonin suppression before bedtime, resulting in circadian misalignment and sleep-onset insomnia; however, whether exposure to evening light disturbs sleep initiation in home settings remains unclear. In this longitudinal analysis of 192 elderly individuals (mean age: 69.9 years), we measured evening light exposure and sleep-onset latency for 4 days using a wrist actigraph incorporating a light meter and an accelerometer. Mixed-effect linear regression analysis for repeated measurements was used to evaluate the effect of evening light exposure on subsequent sleep-onset latency. The median intensity of evening light exposure and the median sleep-onset latency were 27.3 lux (interquartile range, 17.9-43.4) and 17 min (interquartile range, 7-33), respectively. Univariate models showed significant associations between sleep-onset latency and age, gender, daytime physical activity, in-bed time, day length and average intensity of evening and nighttime light exposures. In a multivariate model, log-transformed average intensity of evening light exposure was significantly associated with log-transformed sleep-onset latency independent of the former potential confounding factors (regression coefficient, 0.133; 95% CI, 0.020-0.247; p = 0.021). Day length and nighttime light exposure were also significantly associated with log-transformed sleep-onset latency (p = 0.001 and p < 0.001, respectively). In conclusion, exposure to evening light in home setting prolongs subsequent sleep-onset latency in the elderly.

Association between light exposure at night and insomnia in the general elderly population: The HEIJO-KYO cohort

“…This advantage enabled us to analysis the associations between LAN intensity and outcomes for actigraphic measurements, although our previous study was limited to report the association between LAN and SOL (Obayashi et al, 2014). In addition to its crosssectional design, the present study has three limitations.…”

Sleep and the endogenous melatonin rhythm of high arctic residents during the summer and winter

“…The production of melatonin is the best marker for circadian timing. Suppression of endogenous melatonin production caused by nighttime exposure to bright light, and/or desynchrony of endogenous melatonin production with an individual's rest-work cycle, may lead to mild/moderate insomnia [2]. There is also evidence to indicate that the quantity and duration of melatonin production are greater during the winter months at high latitudes [3][4][5][6], and that increased duration of melatonin production contributes to fatigue and increased negative affect [7].…”

How Much Lighting is Required to Feel Safe When Walking Through the Streets at Night?

“…Public space lighting (PSL), if adequately designed, promotes the feeling of safety (FoS), increases comfort, defines spaces, and forms neighborhood identities [1]. However, if excessive or misdirected, PSL leads to energy waste, increases greenhouse gas emissions [2,3], and poses non-negligible threats to human health [4][5][6][7] and natural ecosystems [8][9][10]. The relation between urban residents and their physical environment is a major field of study in environmental psychology [11,12].…”