Association of sleep variability and irregularity with gestational metabolic syndrome: a birth cohort study.

Background: Pregnant women exhibit a high prevalence of sleep disturbances; however, the relationships between sleep variability, sleep irregularity, and gestational metabolic syndrome (GMS) remain poorly understood. This study aimed to investigate prospective associations of sleep variability and irregularity with the odds of GMS and its individual components. Methods: Four sub-cohorts of pregnant women were established based on data from the Fujian Birth Cohort Study (FJBCS) collected from 2019 to 2021. Logistic regression models were adopted to assess the associations between sleep variability and irregularity during pregnancy and the occurrence of GMS and its components. Stratified analyses examined potential modification of effects by demographic factors. Restricted cubic spline (RCS) models were used to evaluate potential non-linear relationships. Results: Greater sleep variability was significantly associated with increased odds of GMS (aOR 1.348; 95% CI: 1.136-1.559) and dyslipidemia (aOR 1.086; 95% CI: 1.019-1.159), although no significant associations were found for hyperglycemia or hypertension. Sleep irregularity exhibited no significant association with GMS or its components. Subgroup analyses revealed increased vulnerability in women of advanced maternal age compared to younger age groups (aOR: 1.536 vs. 1.279). Those with a history of two or more prior pregnancies and natural pregnancies were more susceptible. RCS modeling confirmed the absence of nonlinear associations. Conclusions: Higher sleep variability is prospectively associated with an increased odds of GMS and dyslipidemia, with potential modulation by maternal age, conception method, and gravidity. No significant association was found between sleep irregularity and GMS or its components.