Maximal weight change during adulthood and breast cancer risk: A 14-year follow-up of the Guangzhou Biobank Cohort Study

Background

Obesity is a risk factor for breast cancer (BC) after menopause, but the association of weight fluctuation during adulthood with BC risk remains unknown.

Methods

A total of 20,056 female participants aged 50 years or older from the Guangzhou Biobank Cohort Study (2003–2008) were followed up until 2020 through linkage with the cancer registry. At baseline, maximal weight change was defined as the difference between the highest and lowest weight since age 18. Cox proportional hazards regression was used, adjusting for potential confounders.

Results

During an average follow-up of 14.2 years, 326 BC cases were identified. A maximal weight gain of 5 kg or more since age 18 was associated with a higher BC risk, compared to a weight change of less than 5 kg (adjusted hazard ratio [adHR] 1.36, 95 % confidence interval [CI] 1.02–1.81; P = 0.03). Among participants who gained 5 kg or more, each additional kilogram was associated with a 2 % higher BC risk (adHR 1.02 per 1 kg, 95 % CI 1.00–1.04; P = 0.02). Similar patterns were found in women who reached the highest weight before the age of 50 (adHR 1.06 per 1 kg, 95 % CI 1.03–1.08; P < 0.001). Additionally, a 1-kg increase in weight was associated with a 10 % (95 % CI 1.05–1.16; P < 0.001) higher risk of BC in women who weighed more than peers at age 20.

Conclusions

These findings suggest that preventing excessive weight gain in adulthood, particularly among women who reached their highest weight before 50 years of age and who were heavier than peers at age 20, may reduce BC risk. Weight management should be emphasized, both at the highest and earliest adult years, in mitigating BC risk.