[Distributions and associations between duration of sleep, daytime naps and insomnia symptoms among Chinese adults].

Objective: To investigate the distribution of sleep duration, daytime naps habits, and insomnia-related symptoms among participants from the China Kadoorie Biobank (CKB) study, and to examine the associations between the sleep-associated factors. Methods: A self-designed computer-based questionnaire was adopted to collect social-demographic information and lifestyle-related factors of the participants. A total of 452 829 Chinese adults aged 30-79 years, without self-reported histories of coronary heart disease, stroke, chronic obstructive pulmonary diseases or cancer, were included in this study. General linear regression and multinomial logistic regression models were used to estimate the distributions on duration of sleep, daytime naps habits, and insomnia-related symptoms in different populations, after adjusted for gender, age, and residential regions. Gender-specific logistic regression model was adopted to examine the associations between the above mentioned sleep-related factors. Results: The average sleep duration of the participants was 7.41 hours per day, with 20.3 % of them having daytime naps all year round, but 40.1 % only had daytime naps in summer, and 39.6 % had no habits of daytime naps. 11.0 % , 10.0 % , and 2.1 % of the participants reported having had symptoms as difficulty in falling asleep, waking up too early or with daytime dysfunction, respectively. There were significant differences on the distributions in sleep-related factors between participants with different gender, age, residential areas, education levels,household income, and marital status ( P <0.05). Results from the logistic regression showed that longer sleep duration was associated with lower risks of insomnia-related symptoms trend ( P <0.001). Factor as without habits of daytime naps seemed to be associated with higher risks of insomnia-related symptoms ( P <0.05). Participants with longer sleep duration were more likely to have the habit of taking daytime naps ( P <0.05). Conclusions: The distributions of sleep duration, habits on daytime naps and insomnia-related symptoms varied according to the differences on social-demographic factors. There were associations existed between the sleeping-related factors, which would influence the promotion on optimal sleep duration and better quality of sleep.