Circadian Rhythm, Sleep Quality, and Health-Related Quality of Life in Korean Middle Adults

Objectives: The aim of this study is to evaluate relationship of health-related quality of life (HRQoL) with chronotype along with quality and quantity of sleep in Korean middle adults. Methods: Data was derived from the nationwide, cross-sectional study on sleep surveyed 2,501 representative adult Koreans. We col lected data from 1,435 participants aged ≥35 years and <65 years to represent Korean middle adults. The Chronotype Questionnaire was used to assess phase and distinctiveness of the circadian rhythm. The Pitts burgh Sleep Quality Index (PSQI) was used to assess sleep quality. Quantity of sleep was investigated by questions regarding sleep habits during workdays and free days. EuroQol-5D 3-level version was used to measure HRQoL. Results: On univariable analyses, eveningness is associated with younger age (47.7±8.2 vs. 51.3±8.1 years, p<0.001), and higher PSQI total score (4.3±2.7 vs. 3.6±2.2, p<0.001) compared with morningness. Strong distinctiveness also associated with higher PSQI total score (4.2±2.3 vs. 3.6±2.5, p< 0.001) compared with weak distinctiveness. Age was not different between the two groups of distinctiveness. On multivariable analyses, strong distinctiveness is an independent factor predicting impairment of pain/ discomfort [odd ratio (OR) 1.589, 95% confidence interval (CI) 1.182–2.130] and depression/anxiety (OR 1.412, 95% CI 1.003–1.987). Poor sleep quality was the most powerful independent factor predicting im pairments in all five domains of the HRQoL. Conclusions: Sleep quality is an important factor indepen dently related to the HRQoL. Among chronotype variables, only distinctiveness has an independent rela tion with the HRQoL.ope