Observational studies have shown that high body mass index (BMI) is associated with a reduced risk of breast cancer in premenopausal women but an increased risk in postmenopausal women. However, it is unclear whether this association is mediated through shared genetic or environmental factors.
In a recent study published in PLOS Medicine, researchers find that genetically predicted high BMI was associated with decreased breast cancer risk both before menopause and after menopause.
Vanderbilt University, University of Cambridge, and University of Melbourne led the study. Researchers examined the association between body mass index and risk of breast cancer using data from two large breast cancer studies.
First, they created a BMI genetic score comprising 84 BMI-associated genetic variants to predicted BMI.
Then they evaluated genetically predicted BMI in association with breast cancer risk using individual-level data from the Breast Cancer Association Consortium (BCAC) (46,325 breast cancer patients and 42,482 healthy people).
After that, they evaluated the association between genetically predicted BMI and breast cancer risk using summary statistics from 16,003 breast cancer patients and 41,335 healthy people from the Discovery, Biology, and Risk of Inherited Variants in Breast Cancer (DRIVE) Project.
The result showed that in the BCAC data, genetically predicted BMI was inversely associated with breast cancer risk. The associations were similar for both premenopausal and postmenopausal breast cancer.
A further analysis showed that 17 of the 84 BMI-associated genetic variants were significantly associated with breast cancer risk. For 16 of them, higher BMI was associated with reduced breast cancer risk.
Researchers suggest that genetically predicted high BMI was associated with decreased breast cancer risk, in pre- and postmenopausal women.
In the future, more research is needed on the interrelationship of genetic factors, environment, and BMI in the risk of breast cancer.
Citation: Guo Y, et al. (2016) Genetically Predicted Body Mass Index and Breast Cancer Risk: Mendelian Randomization Analyses of Data from 145,000 Women of European Descent. PLoS Medicine 13: e1002105. DOI:10.1371/journal.pmed.1002105.
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