Maternal early pregnancy body mass index and risk of insomnia in the offspring.

Study objectives: To investigate the association between maternal early pregnancy body mass index (BMI) and risk of offspring insomnia.

Methods: We conducted a nationwide cohort study among 3,281,803 singleton live births in Sweden born 1983-2015. Using national registries with prospectively recorded information, we followed participants for an insomnia diagnosis from 2 to up to 35 years of age. We compared insomnia risks by early pregnancy BMI categories using hazard ratios (HR) with 95% confidence intervals (CI) from adjusted Cox models. To assess unmeasured shared familial confounding, we conducted sibling-controlled analyses among 1,724,473 full siblings and studied the relation of maternal full sisters' BMI and insomnia risk in 1,185,998 offspring.

Results: There were 7,154 insomnia diagnoses over a median follow-up age of 17.9 years. Compared with women with normal BMI, adjusted HR (95% CI) of offspring insomnia for early pregnancy BMI categories overweight, obesity class I, and obesity classes II or III were, respectively, 1.22 (1.14, 1.30), 1.60 (1.45, 1.77), and 2.11 (1.83, 2.45). Corresponding adjusted HR (95% CI) in sibling comparisons were, respectively, 1.32 (1.05, 1.65), 1.48 (1.03, 2.14), and 1.56 (0.91, 2.65). Associations with maternal sisters' BMI were attenuated, suggesting a weak role for unmeasured shared factors. Other pregnancy, birth, and neonatal complications were associated with risk of insomnia in offspring but did not substantially mediate the association.

Conclusions: The dose-response relation between maternal overweight and obesity severity with offspring insomnia risk is not fully explained by shared familial factors.