Birth Weight, Adult Weight Gain Associated With Breast Cancer Risk

Weight gain in adulthood is associated with an increased risk of breast cancer, according to a study published in the International Journal of Cancer. In addition, lower birth weight is associated with a lower risk of postmenopausal breast cancer.

Researchers assessed 70,397 postmenopausal women aged 50 to 79 years who did not have breast cancer at enrollment (1993‐1998). This cohort was followed for up to 25 years. Weight and height were measured at baseline. Patients also self-reported birth weight and weights at 18, 35, and 50 years.

Birth weight, adult weight gain impact breast cancer risk

Compared with women who weighed 6 to 8 pounds at birth, those with a birth weight of less than 6 pounds had a lower risk of breast cancer (hazard ratio = 0.88; 95% CI, 0.79‐0.99). However, a birth weight of 8 or more pounds was not associated with a risk of postmenopausal breast cancer.

Forty-four percent and 21% of the relationship between birth weight and breast cancer risk was “significantly mediated” by adult height and weight at baseline, respectively. Weight gain in adulthood was associated with increased risk of breast cancer regardless of time periods. Obesity in late adulthood (defined as age 50 years or older) was associated with increased postmenopausal breast cancer risk.

“Our data suggest that reaching and maintaining a healthy weight during adulthood is key in the prevention of breast cancer,” the researchers concluded.