Association between phthalate exposure and sleep quality in pregnant women: Results from the Korean Children’s Environmental Health Study with repeated assessment of exposure

Background: Evidence linking environmental toxicants to sleep quality is growing; however, these associations during pregnancy remain unclear. We examined the associations of repeated measures of urinary phthalates in early and late pregnancy with multiple markers of sleep quality among pregnant women. Methods: The study population included 2324 pregnant women from the Korean Children’s Environmental Health Study. We analyzed spot urine samples collected at two time points during pregnancy for exposure biomarkers of eight phthalate metabolites. We investigated associations between four summary phthalates (all phthalates: ∑Phthalates; di-(2-ethylhexyl) phthalate: ∑DEHP; phthalates from plastic sources: ∑Plastic; and antiandrogenic phthalates: ∑AA) and eight individual phthalates and self-reported sleep measures using generalized ordinal logistic regression and generalized estimating equations models that accounted for repeated exposure measurements. The models were adjusted for age, body mass index, education, gestational age, income, physical activity, smoking, occupation, chronic diseases, depression, and urinary cotinine levels. Results: Multiple individual phthalates and summary measures of phthalate mixtures, including ∑Plastic, ∑DEHP, ∑AA, and ∑Phthalates, were associated with lower sleep efficiency. To illustrate, every 1-unit log increase in ∑AA was associated with a reduction of sleep efficiency by 1.37 % (95% confidence interval [CI] = –2.41, –0.32). ∑AA and ∑Phthalates were also associated with shorter sleep duration and longer sleep latency. Associations between summary phthalate measures and sleep efficiency differed by urinary cotinine levels ( P for subgroup difference < 0.05). Conclusions: Findings suggest that higher phthalate exposure may be related to lower sleep efficiency, shorter sleep duration, and prolonged sleep latency during pregnancy.