Differential Impact of Sleep Duration on Fasting Plasma Glucose Level According to Work Timing

Background and aim: To quantify the differential contribution of sleep duration on fasting plasma glucose level by traditional regular daytime work and shift work in subjects without diabetes.

Methods: Self-reported sleep duration and work type and timing were determined in a cross-sectional sample of 9123 participants aged 20-65 years from the Korea National Health and Nutrition Examination Survey (KNHANES) 2010-2015. Those who responded that they worked between 6 am and 6 pm were classified as "traditional regular daytime workers; "those who worked in the afternoon, at night, or in several types of shift work were classified as "shift workers." FBG was compared between short (<6 h), "normal" (6-8), and long (>8 h) sleep duration groups according to work time.

Results: In the traditional daytime workers group, mean FBG level showed a U-shaped trend according to sleep duration (p = 0.027), whereas in shift workers group, FBG level was significantly decreased across sleep duration (p = 0.001). In the regular daytime workers group, short sleep duration was associated with higher FBG (B, 95% [CI]: 1.33 [0.26-2.4]), whereas after adjustment for potential confounding variables, long sleep duration significantly increased the risk of higher FBG (2.01 [0.35-3.68]). On the other hand, the reverse was true in the shift workers. Long sleep duration was significantly associated with lower FBG by both unadjusted analysis and after multivariable adjustment (-3.79 [-5.97 to -1.62], -2.19 [-4.35 to -0.03], respectively).

Conclusion: Our results suggest that the impact of sleep duration on FBG level differs according to work shift.