Higher childhood BMI may lower later breast cancer risks
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Having a higher childhood BMI may be protective against both premenopausal and postmenopausal breast cancer, according to data presented at the European Congress on Obesity annual meeting.
“We knew from the literature that a larger body size in childhood may protect against premenopausal breast cancer, but less was known about whether childhood BMI related to risks of postmenopausal breast cancer,” Dorthe C. Pedersen, PhD, of the department of public health and epidemiology at Bispebjerg and Frederiksberg Hospital in Copenhagen, Denmark, told Healio. “Therefore, it was surprising to see that a higher childhood BMI may also protect against postmenopausal breast cancer because this contrasts with how a higher BMI at adult ages is associated with increased risks of postmenopausal breast cancer.”
Pedersen and colleagues analyzed data from 173,373 women in the Copenhagen School Health Records Register who were born from 1930 to 1996 and had height and weight measurements available from age 7 to 13 years. The data were linked to the Danish Cancer Registry to identify women who had breast cancer. Women who were aged 55 years or younger at diagnosis were identified as having a premenopausal breast cancer, and those older than 55 years were considered to have a postmenopausal breast cancer.
During 50 years of follow-up from 1968 to 2017, 4,051 women were diagnosed with premenopausal breast cancer and 5,942 with postmenopausal breast cancer. An increase in BMI z score at all childhood ages was associated with a lower risk for premenopausal breast cancer. The risk was consistent and similar at all age groups, including at age 7 years (HR = 0.93; 95% CI, 0.9-0.96) and 13 years (HR = 0.94; 95% CI, 0.9-0.97).
An increased childhood BMI z score was also associated with a lower risk for postmenopausal breast cancer. As with premenopausal breast cancer, the association between childhood BMI and postmenopausal breast cancer was consistent from age 7 years (HR = 0.9; 95% CI, 0.88-0.93) to 13 years (HR = 0.89; 95% CI, 0.87-0.92).
Pedersen noted that a higher childhood BMI may be protective against breast cancer, but it is not recommended that girls gain excess weight because of the numerous adverse health effects associated with a higher BMI.
It is unknown why a higher BMI during childhood may be protective against premenopausal and postmenopausal breast cancer, but Pedersen said girls with a higher BMI may be more likely to also have a higher BMI in young adulthood, which may lower their level of progesterone. Future studies are needed to examine the associations in greater detail.
“We will expand our research by looking into how childhood BMI relates to risks of hormone receptor subtypes of breast cancer,” Pedersen said. “Further, and importantly, studies are needed to understand the biological mechanisms driving the associations that we found.”
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Pedersen DC, et al. Body mass index in childhood and its associations with risks of pre- and postmenopausal breast cancer. Presented at: European Congress on Obesity Annual Meeting; May 10-13, 2021; (virtual meeting).
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