0688 IMPACT OF CIRCADIAN MISALIGNMENT AND BMI ON GLUCOSE DYSREGULATION IN NIGHT-SHIFT WORKERS

Abstract

Epidemiological studies suggests that night shift workers are at increased risk for obesity and diabetes, and simulated shift work studies in day workers have implicated circadian misalignment as a culprit for reduced glucose tolerance. However, this has not been tested in actual night shift workers. To better understand the role of circadian misalignment on glucose dysregulation, we examined glucose tolerance in a sample of fixed night shift workers. Thirty fixed night shift workers participated in this study. All subjects were given an eight-hour opportunity to sleep upon arrival at the lab, and remained under dim-light conditions for 24 hours. An oral glucose tolerance test was administered two hours after awakening. The change in glucose from fasting to one hour after glucose intake, and from fasting to two hours after glucose intake were measured. Melatonin was also assayed via hourly salivary samples, and circadian phase was indexed using the dim light melatonin onset (DLMO). Analyses included years of night shift work as a covariate. Partial correlations controlling for years of shift work indicated that DLMO was not significantly associated with change in glucose tolerance at one-hour, r(27) = .07, p>.05, or at two-hour, r(27) = -.24, p>.05. However, DLMO was significantly associated with glucose tolerance when accounting for weight. Specifically, overweight shift workers (BMI ≥ 26) with earlier DLMOs showed lower glucose tolerance at the two-hour time point, r (15) = -.46, p<.05, compared to subjects with healthy weight, r (9) = .06, p>.05. Results suggest that circadian misalignment alone may not be a significant predictor for glucose dysregulation, but instead may interact with other risk factors for diabetes, such as weight. Thus, increased risk for diabetes in night shift workers should not be generalized, but rather considered only when circadian disturbance is paired with pre-existing risk factors. Our project was funded by TEVA pharmaceuticals.