0081 FOOD INTAKE DURING EARLY MORNING SHIFTWORK AS A NOVEL RISK FACTOR FOR METABOLIC DYSREGULATION

Abstract

Introduction: Increased risk of obesity and metabolic diseases in night and shift workers is thought to be related to caloric intake at adverse circadian times. Over 20% of adults in the US work non‐traditional hours and thus eat some of their meals during the biological night. Little is known, however, about metabolic disease risk in the largest population of shift workers in the US, i.e., early morning shift workers who start work between 0400‐0700h. We therefore tested the impact of simulated early morning shiftwork on glucose metabolism. Methods: 18 subjects (9 female) aged 23.2 ± 3.8y (±SD) completed the 16‐day randomized, counterbalanced, within‐subject protocol. Subjects were healthy based on Clinical and Translational Research Center and PSG sleep disorders screens. Subjects maintained habitual, self‐selected 8h sleep schedules for one‐week prior to each of two study visits: the control condition where subjects slept 8h at their habitual time and the simulated early morning shiftwork condition where subjects went to bed ∼1h prior to habitual bedtime and woke up ∼2.5h prior to habitual waketime (based on unpublished data from early morning shiftworkers collected by our laboratory). After waking, baseline blood glucose, insulin and melatonin levels were sampled then subjects were served the same breakfast 45min after awakening consisting of 25% of daily caloric needs (30% fat, 55% carbohydrate, 15% protein). Blood was then sampled every ∼40min for the next 2h. Results: The early morning shiftwork condition induced morning circadian misalignment and thus melatonin levels were significantly higher on the day of the early shift compared to the habitual wake time condition (p<0.05). Morning circadian misalignment increased glucose levels by ∼5% in response to breakfast (p<0.05) in the early shiftwork compared to habitual wake time condition. This percent change is similar in magnitude to that found in prior forced desynchrony protocols. No significant differences in insulin were observed for condition. Conclusion: Early morning shiftwork may contribute to risk of diabetes by inducing circadian misalignment and higher morning glucose levels associated food intake during the biological night.