Sleep Characteristics and Long-Term Risk of Type 2 Diabetes Among Women With Gestational Diabetes.

Importance: Women with a history of gestational diabetes (GD) are at high risk for developing type 2 diabetes (T2D). Sleep is a crucial lifestyle factor associated with cardiometabolic health, yet studies on its role in the progression from GD to T2D are sparse. Objective: To investigate the associations of sleep duration and quality with T2D risk and levels of glucose metabolism biomarkers in women with a history of GD. Design, Setting, and Participants: This cohort study used data from the Nurses' Health Study II, an ongoing longitudinal cohort that began in 1989 and initially included 116 429 female nurses with health status and lifestyle factors updated every 2 to 4 years. A subset of participants with a history of GD was followed up through June 2021. Sleep characteristics were assessed in the 2001 questionnaire (administered from June 2001 to June 2003), which served as the baseline for follow-up. Data were analyzed from November 2023 to August 2024. Exposures: Snoring frequency, sleep duration, and daytime sleepiness. Main Outcomes and Measures: Physician-diagnosed incident T2D was ascertained biennially via questionnaires. Cox proportional hazards regression models were used to estimate the hazard ratios (HRs) and 95% CIs. Biomarkers (glycated hemoglobin [HbA1c], C-peptide, and insulin) were compared across sleep characteristic categories using multivariable-adjusted least-squares means (LSMs) and 95% CIs. Results: During a total of 42 155 person-years of follow-up among 2891 women with a history of GD (mean [SD] age, 45.3 [4.4] years), 563 women (19.5%) developed T2D. Compared with women who reported rarely snoring, those with occasional or regular snoring had significantly higher T2D risk, with adjusted HRs of 1.54 (95% CI, 1.18-2.02) and 1.61 (95% CI, 1.21-2.13), respectively. Compared with women who slept 7 to 8 hours per day, shorter sleep duration (≤6 hours per day) was significantly associated with a higher risk of T2D (HR, 1.32; 95% CI, 1.06-1.64). Women who slept 6 or fewer hours per day and snored regularly had the highest risk of developing T2D (HR, 2.06; 95% CI, 1.38-3.07). Additionally, more frequent snoring was associated with higher HbA1c (LSM, 5.89; 95% CI, 5.75-6.02), C-peptide (LSM, 4.30; 95% CI, 3.70-4.99), and insulin (LSM, 11.25; 95% CI, 8.75-14.40) levels in the full adjusted models (P = .01 for trend for all). Conclusions and Relevance: In this cohort study of women with a history of GD, shorter sleep duration and both occasional and regular snoring were significantly associated with an increased risk of T2D. These findings suggest that improving sleep health may be important to reduce T2D incidence in this high-risk population.