While late chronotype and greater social jetlag have been associated with poor dietary behavior among the general population, these associations have not been investigated among workers, who struggle to align their sleep timings with work schedules. We aimed to explore the cross-sectional association of social jetlag and a late chronotype with adherence to a healthy diet among Japanese workers. Participants were 1,435 non-shift workers (18-78 years) who attended a nutritional survey. Social jetlag was defined as the difference in the midpoint of sleep times between weekdays and weekends, while chronotype was estimated using the mid-sleep time on weekends that was corrected with sleep debt on weekdays. We calculated the adherence score of the Japanese Food Guide Spinning Top (JFGST) - healthy diet guidelines for Japanese. Multivariable linear regression analyses were used to calculate the adjusted means and 95% confidence intervals (CI) for adherence scores of social jetlag and chronotype. We found that greater social jetlag was associated with a lower JFGST score. The multivariable-adjusted mean (95% CI) of JFGST scores were 39.7 (39.1-40.2), 38.7 (37.9-39.6), and 38.1 (36.6-39.7) for <1 hour, 1 to <2 hours, and ≥2 hours of social jetlag, respectively (P-trend = 0.02). Workers with late chronotypes had significantly lower adherence scores on JFGST [36.3 (34.7-37.8); P-trend = 0.002]. Results suggest that a late chronotype and social jetlag are inversely associated with adherence to a healthy diet among Japanese workers.
Keywords: Japanese diet; Social jetlag; chronotype; restricted cubic spline regression; workers.