Leisure-time physical activity and breast cancer risk by hormone receptor status: effective life periods and exercise intensity.
OBJECTIVE
Physical activity may decrease breast cancer risk. However, it is unclear what intensity of exercise and during which life periods this effect on decreasing risk is efficiently expressed, and whether the associations differ by the estrogen-/progesterone- receptor (ER/PR) status of tumors. We investigated associations between age- and intensity-specific leisure-time physical activity and ER/PR-defined breast cancer risk.


METHODS
We conducted a hospital-based case-control study in Nagano, Japan. Subjects were 405 cases newly diagnosed (>99% known ER/PR) from 2001 to 2005, who were age-/area-matched with 405 controls. Activity was assessed with a self-reported questionnaire which considered intensity level (moderate and/or strenuous) at different ages (at 12 and 20 years, and in the previous 5 years). Odds ratios (ORs) and 95% confidence intervals were calculated using logistic regression.


RESULTS
Strenuous but not moderate physical activity at age 12 was inversely associated with pre- and postmenopausal breast cancer risk across ER/PR subtypes [overall OR(≥ 5 days/week vs. none) = 0.24 (0.14-0.43)]. Moderate physical activity in the previous 5 years was significantly associated with a decrease in risk for postmenopausal ER + PR + tumors only [OR(≥ 1 day/week vs. none) = 0.35 (0.18-0.67)].


CONCLUSIONS
Strenuous activity in teens and moderate activity after menopause may contribute to a reduction in breast cancer risk.
Suzuki
Reiko
R
Epidemiology and Prevention Division, Research Center for Cancer Prevention and Screening, National Cancer Center, Tsukiji 5-1-1, Chuo-ku, Tokyo 104-0045, Japan.
Iwasaki
Motoki
M
Kasuga
Yoshio
Y
Yokoyama
Shiro
S
Onuma
Hiroshi
H
Nishimura
Hideki
H
Kusama
Ritsu
R
Shimazu
Taichi
T
Tsugane
Shoichiro
S
D000328:Adult; D001943:Breast Neoplasms / Q000453:epidemiology / Q000209:etiology*; D016022:Case-Control Studies; D002648:Child; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D007899:Leisure Activities; D008593:Menopause; D008875:Middle Aged; D009043:Motor Activity; D017698:Postmenopause; D011960:Receptors, Estrogen / Q000032:analysis; D011980:Receptors, Progesterone / Q000032:analysis; D012306:Risk
D011960:Receptors, Estrogen; D011980:Receptors, Progesterone