Overnight wakefulness impairs next-day postprandial glucose in young women independent of sex hormones

Abstract Context Estradiol and progesterone may influence glucose regulation, but it remains unclear whether ovarian hormone levels modulate night shift–induced impairments in glucose metabolism. Objective To investigate the effects of a night shift–like schedule on next-morning fasting and postprandial glucose metabolism in reproductive-aged women. Methods Fifty-two women with an HbA1c 5.7% completed a protocol consisting of one night of sleep and one night of wakefulness in a laboratory environment. After each night, fasting blood samples were collected to measure estradiol, progesterone, insulin, leptin, and adiponectin. Insulin resistance was estimated using HOMA-IR, and the leptin-to-adiponectin ratio (LAR)—a marker of fasting and postprandial insulin sensitivity—was calculated. Morning postprandial glucose responses were assessed using an oral glucose tolerance test (OGTT), and substrate utilization was measured via respiratory quotient (RQ) using indirect calorimetry. Linear mixed-effects models were used to test the effects of condition and the progesterone-to-estradiol (P/E) ratio on all outcomes. Results Fasting glucose, HOMA-IR, and LAR did not differ between conditions. Post-OGTT blood glucose at 60 minutes (mean estimated difference: 0.58 mmol/L, p = 0.016) and peak glucose (0.42 mmol/L, p = 0.037) were higher following the night shift compared with sleep. The P/E ratio was not significantly associated with fasting or postprandial glucose. Pre-OGTT RQ was lower after the night shift (-0.029, p 0.001), and adjusting for pre-OGTT RQ attenuated the post-OGTT glucose differences between conditions (p ≥ 0.097). Conclusion One night of wakefulness—as occurs in night shift work—impaired next-morning glucose tolerance in women, independent of ovarian hormone variation. Accordingly, choosing low–glycemic index foods for the first meal after a night shift may help reduce postprandial glucose excursions.