Adulthood lifetime physical activity and breast cancer.
BACKGROUND
Epidemiologic studies have shown that breast cancer risk is reduced 30% to 40% in highly physically active compared with inactive women. However, the effects of moderate activities, timing of activities, and intervening effects of other risk factors remain less clear.


METHODS
We analyzed data on physical activity patterns in 2176 incident breast cancer cases and 2326 controls in a population-based breast cancer case-control study in Poland conducted in 2000-2003. Using unconditional logistic regression analyses, we calculated odds ratios (ORs) and 95% confidence intervals (CIs) associated with physical activity levels (measured by average metabolic equivalents of energy expenditure hours per week), controlling for potential confounders.


RESULTS
Total adult lifetime activity reduced risk of breast cancer, with individuals in the highest quartile having an OR of 0.80 (CI = 0.67-0.96) compared with the lowest quartile. Reduced risks were most consistent for the highest quartiles of moderate-to-vigorous activities: moderate/vigorous recreational activities (OR = 0.74; CI = 0.62-0.89), outdoor activities (0.81; 0.68-0.97), heavy physical work (0.60; 0.42-0.87), and combined high intensity (metabolic equivalent >6.0) activities (0.75; 0.63-0.90). These relations were not modified by body mass index, menopausal status, or family history of breast cancer. Reductions in risk with moderate/vigorous recreational activities were stronger for larger tumors and those with nodal involvement. Women who increased their recreational activity in their 50s had significantly reduced risk, with those in the highest tertile of change being at a 27% lower risk.


CONCLUSIONS
Leisure-time moderate-to-vigorous activities reduce breast cancer risk irrespective of underlying host characteristics.
Peplonska
Beata
B
Department of Occupational and Environmental Epidemiology, Nofer Institute of Occupational Medicine, Lodz, Poland. beatap@imp.lodz.pl
Lissowska
Jolanta
J
Hartman
Terryl J
TJ
Szeszenia-Dabrowska
Neonila
N
Blair
Aaron
A
Zatonski
Witold
W
Sherman
Mark E
ME
Garcia-Closas
Montserrat
M
Brinton
Louise A
LA
D000328:Adult; D000367:Age Factors; D000368:Aged; D001943:Breast Neoplasms / Q000453:epidemiology* / Q000517:prevention & control*; D016022:Case-Control Studies; D015987:Effect Modifier, Epidemiologic; D004734:Energy Metabolism; D015444:Exercise / Q000502:physiology; D005260:Female; D006801:Humans; D007407:Interviews as Topic; D016015:Logistic Models; D008875:Middle Aged; D011044:Poland / Q000453:epidemiology; D011998:Recreation; D012042:Registries; D012307:Risk Factors