Study question: What is the association between late bedtime, night sleep duration, and lifetime cardiovascular disease (CVD) risk in women with polycystic ovary syndrome (PCOS)?
Summary answer: Both late bedtime (≥1:00) and short sleep duration (<7 h/night) were independently associated with a high-lifetime CVD risk among women with PCOS.
What is known already: Previous studies indicated that sleep disturbances, including altered sleep duration and staying up late (SUL), occurred more frequently among women with PCOS compared to women without PCOS. Studies have shown that both PCOS and sleep disturbances are associated with deterioration in cardiometabolic health in the longer term. However, there are limited data regarding the possible association between sleep disturbances and CVD risk among reproductive-aged women with PCOS.
Study design, size, duration: From the original 393 women identified at our center, a total of 213 women with PCOS aged 18-40 years were enrolled in a cross-sectional study between March 2020 and July 2022.
Participants/materials, setting, methods: Bedtime and night sleep duration were obtained from a standardized self-administered questionnaire. The prediction for atherosclerotic CVD risk in the China risk model was applied to estimate the lifetime CVD risk in the PCOS population. Restricted cubic spline regression was applied to explore the non-linear association between sleep duration and lifetime CVD risk in a series of models. Multivariable logistic regression analyses were performed to determine the association between bedtime, night sleep duration, and lifetime CVD risk.
Main results and the role of chance: In our study, we found that the proportion of SUL was 94.25% and the mean (±SD) of night sleep duration was 7.5 ± 1.1 h in women with PCOS. Restricted cubic spline regression analysis showed a U-shaped relation between sleep duration and lifetime CVD risk. After adjusting for occasional drinking, fasting insulin, triglyceride, low-density lipoprotein cholesterol, and testosterone in multivariable logistic analyses, compared with going to bed at 23-24 o'clock, those who went to bed after 1 o'clock were independently associated with high-lifetime CVD risk [odds ratio (OR) = 3.87, 95% CI: 1.56-9.62]; compared with optimal sleep duration (7-8 h/night), short sleep (<7 h/night) was also independently associated with high-lifetime CVD risk (OR = 2.46, 95% CI: 1.01-5.97).
Limitations, reasons for caution: Inferring causality is limited owing to the cross-sectional design. All sleep variables data were obtained from a standardized self-administered questionnaire rather than measurements using objective approaches. Even after adjusting for potential confounders, we still cannot completely rule out the possibility of residual confounding from unmeasured factors such as socioeconomic status. Future studies with larger sample sizes are needed to further explore the relation between long sleep duration and lifetime CVD risk. Although these findings are not generalizable to non-SUL PCOS populations, they could be used for guiding multidimensional treatment. Lastly, there is no non-PCOS group in the current cross-sectional study, which limits the interpretation of the findings from the PCOS group.
Wider implications of the findings: This is the first study to report that both late bedtime (≥1:00) and short sleep duration (<7 h/night) were independently associated with a high-lifetime CVD risk among reproductive-aged women with PCOS, in a sample of Chinese adults. Predicting cardiovascular risk and examining the association between sleep disturbances and predicted CVD risk among women with PCOS help to highlight the need for early interventions on sleep to improve their cardiovascular outcomes.
Study funding/competing interest(s): This study was funded by the Natural Science Foundation of Fujian Province (No. 2020J011242), the Fujian provincial health technology project (No. 2022CXB016), the Joint Research Projects of Health and Education Commission of Fujian Province (No. 2019-WJ-39), and the Medical and Health project of Xiamen Science & Technology Bureau (No. 3502Z20214ZD1001). The authors declare that they have no conflict of interest.
Trial registration number: N/A.
Keywords: PCOS; bedtime; cardiovascular diseases; night sleep duration; polycystic ovary syndrome; risk assessment.
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