A significantly decreased risk of endometrial cancer was reported among participants with a history of pregnancy compared to those nulliparous.
According to a recent study published in JAMA Network Open, late menarche, early menopause, and an increased number of deliveries are significantly associated with decreased risk of endometrial cancer.1
Endometrial cancer is the sixth most common cancer in women, at a rate of 21.1 per 100,000 in the United States. Differences in endometrial cancer incidence have been observed based on race and geographical location. However, there is limited data on how reproductive factors influence the risk of endometrial cancer.
The endometrium is influenced by the menstrual cycle, shifting based on estrogen and progesterone levels. Therefore, reproductive factors including parity, age at menarche, and menopause may impact endometrial cancer risk.
To evaluate the association between reproductive factors and risk of endometrial cancer in an Asian cohort, investigators pooled 13 prospective cohort studies from the Asia Cohort Consortium (ACC), a consortium of prospective cohort studies in Asia. Of the ACC studies chosen, 8 were conducted in Japan, 3 in Korea, 1 in China, and 1 in Singapore.
Data collected in the cohort studies included reproductive factor data, endometrial cancer incidence, follow-up duration, and potential cofounders. Exclusion criteria included male sex, missing sex and age data, endometrial cancer history at baseline, missing or no follow-up duration, hysterectomy history at baseline, missing parity data, and body mass index (BMI) under 14 or above 45.
Exposures included number of deliveries, age at first delivery, age at menarche, and menopause. Questions pertaining to these exposures were asked in a baseline questionnaire, along with breastfeeding status and hormone therapy status.
Endometrial cancer incidence was determined through linkage to local cancer registries. Cancer data included primary cancer and whether endometrial cancer was a primary cancer, secondary, or more. Cofounders included BMI, age, current alcohol consumption status, and current smoking status.
There were 332,625 women included in the final analysis, aged a mean 54.3 years. Pregnancy was reported by over 90% of participants, and a majority experienced menarche when aged 13 to 16 years and menopause when aged 45 to 54 years.
A significantly decreased risk of endometrial cancer was reported among participants with a history of pregnancy compared to those nulliparous. A negative correlation was found between the number of deliveries and endometrial cancer risk. Significant associations were also found between endometrial cancer risk and older age at menarche and younger age at menopause.
These results indicated impacts of late menarche, early menopause, and number of deliveries on endometrial cancer risk. Investigators recommended future studies with full adjustment to confirm these results.