Swedish researchers studied childhood body size and tumour characteristics in a group of 2,818 Swedish breast cancer patients and 3,111 controls. Researchers asked women to assess their body type at present and how they remembered themselves at seven years old.
These selections were then used to group participants as lean, medium or large. Overall researchers found that a large body type at age seven years was associated with a decreased risk of postmenopausal breast cancer.
Researchers report that although strongly associated with other known risk factors such as age of menarche, adult BMI and breast density, size at age seven years remained a significant protective factor after adjustment for these other issues.
Size at age seven was also found to determine tumour characteristics, in particular, estrogen receptor status. A large body size at age seven was especially protective against estrogen receptor negative tumours, which generally fare worse in terms of prognosis.
Researchers conclude that it appears counterintuitive that a large body size during childhood can reduce breast cancer risk, because a large birth weight and a high adult BMI have been shown to otherwise elevate breast cancer risk. Further research is needed to examined this relationship and determine the protective mechanism.
The study was published in the journal Breast Cancer Research.