Birth Size Linked to Breast Cancer Risk

October 2, 2008

Birth size, particularly birth length, is associated with the risk of breast cancer, according to a report published online Sept. 30 in PLoS Medicine.

THURSDAY, Oct. 2 (HealthDay News) -- Birth size, particularly birth length, is associated with the risk of breast cancer, according to a report published online Sept. 30 in PLoS Medicine.

Isabel dos Santos Silva, M.D., Ph.D., from the London School of Hygiene and Tropical Medicine in the United Kingdom, and colleagues reviewed data from 32 studies involving 22,058 breast cancer cases to examine whether birth size affects breast cancer risk.

The researchers found that increased birth weight increased breast cancer risk in studies where weight was available from birth records (pooled relative risk for each 0.5 kg increase in birth weight, 1.06). Birth length and head circumference, when obtained from birth records, was also associated with breast cancer risk (pooled relative risk 1.06 and 1.09, respectively, per standard deviation). Of the three birth size measures, birth length was the strongest independent predictor of risk, the report indicates. Accounting for known breast cancer risk factors had little effect. The cumulative incidence of breast cancer per 100 women by 80 years of age increased from 10.0 for the bottom fourth to 11.5 for the top fourth of birth length.

The study "has provided the strongest evidence yet that birth size is a critical determinant of breast cancer risk in adult life," Pagona Lagiou, M.D., Ph.D., and Dimitrios Trichopoulos, M.D., Ph.D., from the Harvard School of Public Health in Boston, write in an accompanying editorial.

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