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

Abstract

Chronic circadian misalignment between the internal and environmental rhythms, which is typically related to night-shift work and clock-gene variants, is associated with disruption of suprachiasmatic nucleus function and increased risk of insomnia. Under controlled laboratory conditions, light at night (LAN) suppresses melatonin secretion, delays the internal biological rhythm, and reduces sleepiness. Therefore, LAN exposure may cause circadian misalignment and insomnia, though it remains unclear in real-life situations whether LAN exposure is associated with insomnia. To evaluate an association between LAN exposure and sleep quality in home settings, we conducted a cross-sectional community-based study in 857 elderly individuals (mean age, 72.2 years). We evaluated bedroom light intensity using a light meter and subjectively and objectively measured sleep quality using the Pittsburgh Sleep Quality Index and an actigraph, respectively, along with urinary 6-sulfatoxymelatonin excretion. Compared with the lowest quartile group of LAN intensity, the highest quartile group revealed a significantly higher odds ratio (OR) for subjective insomnia in a multivariate model adjusted for age, gender, body mass index, daytime physical activity, urinary 6-sulfatoxymelatonin excretion, bedtime, rising time, and day length (adjusted OR, 1.61, 95% confidence interval, 1.05-2.45, p=0.029). In addition, higher OR for subjective insomnia was significantly associated with the increase in quartiles of LAN intensity (ptrend=0.043). Consistently, we observed significant association trends between the increase in quartiles of LAN intensity and poorer actigraphic sleep quality, including decreased sleep efficiency, prolonged sleep-onset latency, increased wake-after-sleep onset, shortened total sleep time, and delayed sleep-mid time in multivariate models adjusted for the covariates mentioned above (all ptrend<0.001). In conclusion, we demonstrated that LAN exposure in home settings is significantly associated with both subjectively and objectively measured sleep quality in a community-based elderly population.

An exploratory study examining the associations between sunlight exposure, sleep behaviours and sleep outcomes during an Arctic summer

“…Therefore, it may be that any amount of evening sunlight exposure is detrimental to sleep. While natural and artificial light during the biological night has been found to negatively affect sleep [24,31,33,34], we found that the amount of evening light after 8 pm was not associated with poorer sleep outcomes. Thus, the timing of light exposure, which we could not assess, may be a more relevant factor and warrants further study.…”

Quantitative association between nocturnal voiding frequency and objective sleep quality in the general elderly population: the HEIJO-KYO cohort

“…In addition, the study included a large sample of objective sleep measurements in a general elderly population. Previous studies have suggested that endogenous melatonin levels and bedroom light intensity are associated with nocturia and sleep quality [28,29]. Typically, NV with the bedroom light turned on might suppress melatonin secretion and lead to sleep disturbance.…”

Systematic review of light exposure impact on human circadian rhythm

“…The subjects were usually from 20 to 40 years old, being somewhat older than in those presented in SM 1. One study was conducted with pre-school children (Akacem et al 2016) and one with elderly (Obayashi et al 2014) adults. Light levels were typically measured for 24 h per day providing insight on the longterm light exposure profiles.…”