Moderate-to-vigorous exercise in a woman's 40's reduces her risk of post-menopausal breast cancer, a recent study found.

The critical factors for risk reduction were:
•" " "  More than 7 hours per week of higher intensity acitivity reduced risk by 16%. Light activity during that decade, or intense activity earlier in life did not reduce risk.
•" " "  Higher intensity activity includes running, swimming, cycling at a high speed or in a spin class, and singles tennis, but not golf, gardening or regular walking.

Potential reasons for protective effects of exercise:
•" " "  Enhanced immunity
•" " "  Reduced or altered levels of sex hormones
•" " "  Reduced inflammation
•" " "  Changes in insulin and insulin-like growth factors
Study facts:
•" " "  Sponsor: NIH-AARP
•" " "  Number of subjects: 118,899 postmenopausal women
•" " "  Age of subjects: 50 to 71 years
•" " "  Location: six states or the Atlanta or Detroit metropolitan areas
•" " "  Information sources: answers to questionnaires at the time of entering the study; follow-up questionnaires.

Moderate-to-vigorous activities such as swimming, tennis, and jogging played a bigger role in women's lives before age 40, but these activities earlier in live did not show protective benefits.

Read the Medical News article
http://www.medpagetoday.com/HematologyOncology/BreastCancer/16240?impressionId=1255570384912
Primary source: BMC Cancer
Source reference:
Peters TM, et al "Intensity and timing of physical activity in relation to postmenopausal breast cancer risk: the prospective NIH-AARP Diet and Health Study" BMC Cancer 2009; DOI: 10.1186/1471-2407-9-349.