Sleep behaviors and time-to-pregnancy: results from a Guangzhou City cohort

Abstract

Introduction: Fertility outcomes are increasingly influenced by modern lifestyle factors, including sleep behaviors. However, the relationship between sleep and time to pregnancy (TTP) is underexplored.

Methods: We conducted a prospective cohort study of 1,684 couples in Guangzhou, China. Sleep behaviors were assessed via structured interviews. Cox proportional hazards models were used to estimate fecundability ratios (FRs), adjusting for potential confounders. Sleep-wake regularity was assessed for all women. Among those with regular patterns (n = 1506), we further analyzed sleep duration, bedtime, perceived sleep sufficiency, and insomnia.

Results: Among all participants, 178 (10.6%) had irregular sleep. Time-varying models revealed that compared to regular sleepers, irregular sleepers exhibited a decreasing fecundability ratio (FR < 1) after approximately 2.6 months of attempting pregnancy, with the association becoming statistically significant after 4.1 months. In women with regular sleep, longer sleep duration was associated with higher fecundability (adjusted FR = 1.18, 95% CI: 1.09-1.27; p < 0.001). Spline analysis indicated a linear increase in fecundability with sleep durations exceeding 7.5 h. Perceived insufficient sleep was linked to reduced fecundability (adjusted FR = 0.62, 95% CI: 0.48-0.81; p < 0.001), while later bedtime was associated with lower fecundability (adjusted FR = 0.91, 95% CI: 0.84-0.98; p = 0.045). Insomnia showed no significant effect (adjusted FR = 0.86, 95% CI: 0.67-1.11, p = 0.241).

Conclusions: Irregular sleep patterns may reduce fecundability over time. Among women with regular sleep, longer duration, earlier bedtime, and sufficient perceived sleep were associated with improved reproductive potential. Sleep optimization could be a modifiable behavioral target to enhance fertility.

Trial registration: ChiCTR2300068809 registered 1/3/2023.

Keywords: Cohort study; Insomnia; Irregular sleep patterns; Sleep duration; Sleep onset time; Time to pregnancy.

Fig. 1

Study population creation

Fig. 2

Time-dependent effect of irregular versus regular sleep patterns on TTP. Note: The red line represents the estimated fecundability ratio (FR) across different TTP months, while the shaded blue region indicates the corresponding 95% CIs. The black dashed line at FR = 1 serves as a reference, representing no effect. A No covariates were adjusted for in the time-dependent Cox regression model. The baseline effect of irregular routines was statistically significant (FR = 2.05; 95% CI: 1.10–3.84; p = 0.025), while the interaction with time was also significant and negative (FR = 0.56; 95% CI: 0.39–0.81; p = 0.002). B The covariates included in the time-dependent Cox regression model were BMI, age, occupation, and education level for both partners, as well as tobacco exposure, frequent consumption of takeaway food, duration of electronic device use, regular menstruation, exercise frequency for women. The baseline effect of irregular routines was statistically significant (FR = 2.05; 95% CI: 1.09–3.85; p = 0.025), while the interaction with time was also significant and negative (FR = 0.56; 95% CI: 0.39–0.81; p = 0.002)

Fig. 3

Restricted cubic spline model of the association between sleep duration and TTP. Note: A Restricted Cubic Spline Model for sleep duration with Adjusting for key sleep-related variables, including sleep onset time, insomnia, and perceived insufficient sleep for women. B Restricted Cubic Spline Model for sleep duration with Adjusting for all covariates, including BMI, age, occupation, and education level for both members of the couple, as well as tobacco exposure, frequent consumption of takeaway food, duration of electronic device use, regularity of menstruation, exercise frequency, sleep onset time, insomnia, and perceived insufficient sleep for women. In both panels, the x-axis denotes sleep duration, and the y-axis indicates the estimated fecundability ratio (FR) with 95% confidence intervals (CI). The gray histogram in the background represents the distribution of sleep duration in the study population, and the black vertical dashed line indicates the reference sleep duration. The black horizontal dashed line indicates the fecundability ratio (FR) = 1

Fig. 4

Restricted cubic spline model of the association between sleep onset time and TTP. Note: A Restricted Cubic Spline Model for sleep onset time with Adjusting for key sleep-related variables, including sleep duration, insomnia, and perceived insufficient sleep for women. B Restricted Cubic Spline Model for sleep onset time with Adjusting for all covariates, including BMI, age, occupation, and education level for both members of the couple, as well as tobacco exposure, frequent consumption of takeaway food, duration of electronic device use, regularity of menstruation, exercise frequency, sleep duration, insomnia, and perceived insufficient sleep for women. In both panels, the x-axis denotes sleep onset time, and the y-axis indicates the estimated fecundability ratio (FR) with 95% confidence intervals (CI). The gray histogram in the background represents the distribution of sleep onset time in the study population, and the black vertical dashed line indicates the reference sleep time. The black horizontal dashed line indicates the fecundability ratio (FR) = 1