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Table 2 Relative risk of postmenopausal breast cancer in relation to total physical activity among US women in the Breast Cancer Detection Demonstration Project (BCDDP; 1987 to 1998)*

From: Prospective study of physical activity and risk of postmenopausal breast cancer

Variable Quintile of total physical activity p
  1 2 3 4 5  
Physical activity       
   MET-hours/week (range) 105 to 244 245 to 297 298 to 339 340 to 394 395 to 721  
   Cases 320 300 308 312 266  
   Person-years 52,858 53,967 54,019 54,487 54,461  
   Age-adjusted RR (95% CI) 1.0 0.92 (0.79 to 1.08) 0.94 (0.81 to 1.10) 0.95 (0.82 to 1.12) 0.81 (0.69 to 0.95) 0.03
   Multivariate RR † (95% CI) 1.0 0.92 (0.79 to 1.08) 0.97 (0.83 to 1.14) 0.98 (0.84 to 1.15) 0.86 (0.73 to 1.01) 0.15
   Multivariate RR ‡ (95% CI) 1.0 0.93 (0.80 to 1.09) 0.98 (0.84 to 1.14) 1.00 (0.85 to 1.16) 0.87 (0.74 to 1.02) 0.21
  1. * CI = confidence interval; MET = metabolic equivalent task; RR = relative risk.
  2. † The multivariate model included the following: age at baseline (continuous), family history of breast cancer (any first- or second-degree relative; yes, no or unknown), history of benign breast disease (any benign breast disease prior to study baseline, including during the screening stages; yes or, no), breast cancer screening history (women who had undergone a breast biopsy as part of the BCDDP screening but lacked evidence of malignant disease, women who were recommended for surgical consultation as part of the BCDDP but for whom the procedure was not performed, or women who represented a random sample of BCDDP participants who had no surgery or recommendation for surgical consultation during BCDDP screening), height (continuous), age at menarche (≤ 11, 12, 13 or 14+ years of age), age at menopause (age at which menstrual period stopped for at least three continuous months; <47 or 47+ years of age), age at first live birth (continuous), history of oral contraceptive use (yes or no), menopausal hormone therapy (ever or never), education attainment (less than or equal to high school, or greater than high school), cigarette smoking (ever or never), and intakes of energy-adjusted dietary fat (continuous) and alcohol (continuous).
  3. ‡ Also controlled for body mass index (continuous).