(HealthDay News) — Greater overall physical activity, greater vigorous activity, and lower sedentary time may reduce the risk of breast cancer, according to a study published online Sept. 6 in the British Journal of Sports Medicine.

Suzanne C. Dixon-Suen, from the Cancer Council Victoria in Melbourne, Australia, and colleagues performed two-sample inverse-variance-weighted Mendelian randomization using data from 130,957 women of European ancestry (69,838 with invasive breast cancer, 6,667 with in situ breast cancer, and 54,452 control individuals) from 76 Breast Cancer Association Consortium studies.

The researchers used genetic estimates for movement-related exposures from published genome-wide association studies using data from the UK Biobank (n=91,105–377,234). They looked at single-nucleotide polymorphisms associated with overall physical activity, vigorous physical activity, or sedentary time.

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The researchers found that greater genetically-predicted overall activity was associated with a lower risk for breast cancer overall (odds ratio, 0.59 per standard deviation) and for most case groups defined by tumor characteristics.

Genetically-predicted vigorous activity was associated with a lower risk for pre/perimenopausal breast cancer (odds ratio, 0.62 for 3 or more days of vigorous activity per week vs 0 days). For most case groups, estimates were consistent.

In addition, greater genetically-predicted sedentary time was associated with a higher risk for hormone-receptor-negative cancer (odds ratio, 1.77 per standard deviation [~7 percent time spent sedentary]). In most case groups, estimates were elevated.

“A stronger cancer-control focus on physical activity and sedentary time as modifiable cancer risk factors is warranted, given the heavy burden of disease attributed to the most common cancer in women,” the authors write.

Several authors disclosed financial ties to the biopharmaceutical industry.

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