Early-life exposure to ambient temperature and polycystic ovary syndrome: a nationwide cohort study

Early-life temperature exposure, especially during oogenesis, may impact ovarian function later in life. However, the effect of ambient temperature during sensitive developmental windows on ovulation disorders remains unknown.

We investigate the associations of early-life ambient temperature exposure with incident polycystic ovary syndrome (PCOS) in the Growing Up Today Study II, a United States (US) nationwide prospective cohort. We included females born after 1989 with available outcome and exposure data during the preconception (N = 3265), gestation (N = 3265), and childhood period (N = 3521). Monthly average residential mean temperatures were estimated using the PRISM Climate Group data. We considered exposure windows included preconception (3 months prior to conception), gestational (from conception month to birth), individual trimesters, and childhood (from birth to 1 year before age at menarche). PCOS was identified by self-reported clinical diagnosis. We estimated adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) for PCOS per interquartile range (IQR) increase of mean temperature using Cox models.

We identified 234 (7.2%) PCOS cases over the 14.3 ± 4.2 years from age at menarche to 2021. Higher ambient temperatures during the preconception (HR 1.38 per 13.4°C, 95% CI, 0.84-2.27), gestation (HR 1.08 per 6.4°C, 95% CI, 0.74-1.60), and childhood (HR 1.20 per 4.1°C, 95% CI, 0.91-1.59) periods were suggestively associated with higher risk of PCOS. In gestation period, only the first-trimester temperature was associated with higher risks of PCOS (HR 1.75 per 14.4°C, 95% CI, 1.06-2.87).

Intervention to mitigate heat exposure during pregnancy, especially in the first trimester, may help reduce the risk of PCOS in offspring. Further research is needed to confirm these associations.