0369 Pre-Awake Light Exposure And Sleep Disturbances: Findings From The HEIJO-KYO Cohort

Abstract Introduction Recent experimental and epidemiological studies indicated that light exposure at night (LAN) is associated with poor sleep quality. We previously reported three LAN exposure phenotypes (i.e. pre-awake, just after bedtime, and constant), which have not yet been examined the relationship with sleep quality. The purpose of this cross-sectional study was to test whether pre-awake light (PAL) exposure relates to sleep quality in a large general population. Methods Among 1106 elderly individuals (mean age, 71.8 years) of the HEIJO-KYO cohort, we measured bedroom light intensity at 1-min intervals and subjective sleep quality using the Pittsburgh Sleep Quality Index (PSQI). Pre-awake period was determined as 120 minutes before rising and sleep disturbances was PSQI score ≥6 or diagnosed insomnia. Results Median PAL intensity was 0.7 lux (interquartile range, 0–5.0). With increases in PAL quartiles, prevalence of sleep disturbance increased (P for trend = 0.001). Compared with the lowest PAL quartile group, the highest PAL quartile group exhibited significantly higher odds ratio (OR) for sleep disturbances (OR, 1.69; 95% CI, 1.19–2.40) independent of age and gender. This association was stronger in individuals with later chronotype (OR, 1.86; 95% CI, 1.09–3.16) than those with earlier chronotype (OR, 1.66; 95% CI, 1.03–2.67). Also, further adjustment for potential confounders such as BMI, smoking and drinking status, diabetes, renal function, physical activity, melatonin levels, bedtime, rising time, day length, and light exposure 4 hour after bedtime did not change the results. Conclusion In our community-based elderly population, PAL exposure is significantly associated with sleep disturbances and that was independent of several potential confounding factors including melatonin levels and light exposure after bedtime. Support (If Any):