Higher BMI in childhood may help protect women against breast cancer in later life, both before and after the menopause

A study of more than 173,000 women in Denmark, presented at the European Congress on Obesity (ECO) held online this year, suggests that girls with a higher body mass index (BMI) are less likely to suffer during childhood than their peers with a lower BMI. develop breast cancer as adults, both before and after menopause.

The findings contrast with those for BMI in adults, which indicate that women who gain weight after menopause have an increased risk of postmenopausal breast cancer. While the authors are unsure why children with a higher BMI appear to be protected against breast cancer, they warn that being overweight or obese can have many adverse effects on general health.

“Our results suggest that having a higher BMI in childhood can lower breast cancer risk both before and after menopause. But we really need to be clear that weight gain should not be seen as a way to prevent breast cancer,” says lead author . Dr Dorthe Pedersen from Bispebjerg and Frederiksberg Hospital, Copenhagen, Denmark. “There are so many health risks associated with being overweight or obese that it is vital for women to maintain a healthy weight throughout their lives.”

Breast cancer is the most common cancer in women, with around 55,000 women diagnosed each year in the UK alone, and nearly 1 in 5 cases develop under the age of 50. Previous research has shown a link between increased BMI in adult women and a lower risk of breast cancer before menopause, but an increased risk after menopause. While a high BMI in children may be protective against the risk of overall breast cancer, previous studies were not large enough to investigate the association by type of menopausal status.

To provide more evidence, Danish researchers analyzed data from 173,373 women from the Copenhagen School Health Records Register born between 1930 and 1996 (ages 25 to 91 now) who had information on height and weight measured during annual school health surveys in the age of 7 to 13 years. years. Breast cancer cases were identified by linking to the Danish Cancer Registry.

During an average of 33 years of follow-up, 4,051 women were diagnosed with breast cancer before menopause (55 years of age or younger) and 5,942 women after menopause (at 55 years).

The analyzes suggest “inverse associations” between BMI in children and breast cancer risk before and after menopause, meaning that breast cancer risk decreases as BMI increases. When comparing two 7-year-old girls with an average height and one z-score difference in BMI (equal to 2.4 kg), the girl with the highest BMI had a 7% lower risk of developing premenopausal breast cancer and a 10% lower risk of developing postmenopausal breast cancer than the girl with the lower BMI.

The authors say further studies are needed to uncover the mechanisms underlying these associations. They recognize that the findings are associations only, so no conclusions can be drawn about cause and effect, and point to several limitations, including that the study used BMI as a marker of fat mass, but children with the same BMI may have different body fat. distributions and overall levels of body fat.

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