[Relationship between bedtime and BMI, waist, blood pressure in college students: a one-year follow-up study]

To assess the relationship between bedtime and metabolic syndrome risk factors in college students.

Participants including 186 male and414 female college students from 2 junior colleges and 1 regular college in Chizhou city were selected using stratified cluster sampling. The data on bedtime and metabolic syndrome was collected in a one-year follow-up survey. The bedtime and sleep quality was evaluated using Pittsburgh sleep quality index. Indexes including body mass index, waist circumference and blood pressure were measured to evaluate metabolic syndrome risk factors.

Compared with the students with bedtime before 12 pm, students with bedtime after 12 pm in baseline survey had significant higher risk for any two metabolic syndrome risk factors in one-year follow-up survey( adjusted OR = 2. 08, 95% CI 1. 08-4. 02). The prevalence of any two metabolic syndrome risk factors significantly increased( Ptrend= 0. 004) across students with bedtime before 12 pm in baseline in baseline survey( 5. 8%), students with bedtime after 12 pm in baseline and bedtime before 12 pm in follow-up survey( 12. 5%), and students with bedtime after 12 pm both in baseline and follow-up survey( 15. 0%). Compared with students with bedtime before 12 pm in baseline, the risk for any two metabolic syndrome risk factors among students in other two groups increased, but did not reach statistical significant( Bedtime before 12 pm: adjusted OR = 1. 92, 95% CI 0. 94- 3. 92, P = 0. 072. Bedtime after 12 pm: adjusted OR = 2. 40, 95% CI 0. 86- 6. 73, P = 0. 096).

Later bedtime is significantly associated with increased risk for metabolic syndrome risk factors in college students, and the risk could not reduced through changing the bedtime during one year.