Table 2.

Relative risk of breast cancer according to measures of recreational physical activity and leisure-time sitting among women of the CPS-II Nutrition Cohort, 1992–2007

RR according to exposure updated in 1999, 2001, and 2005
Cases/person-yearsRateaRR (95% CI)bRR (95% CI)c
MET-h/wk total recreational physical activity
 None370/77,3164780.91 (0.81–1.02)0.91 (0.81–1.02)
 >0–7.01,706/317,6975331.001.00
 >7–17.51,428/274,5645190.97 (0.90–1.04)0.97 (0.90–1.04)
 >17.5–31.5875/164,8085220.99 (0.91–1.07)0.99 (0.92–1.08)
 >31.5–42.0238/46,9554990.93 (0.81–1.07)0.94 (0.82–1.08)
 >42.0143/35,5663930.74 (0.62–0.88)0.75 (0.63–0.89)
Ptrend = 0.05 (active women only; Ptrend = 0.01)c,f
Walking h/wk
 None370/77,3164780.89 (0.79–0.99)0.89 (0.79–1.00)
 ≤3 h/wk walking only1,474/267,8265461.001.00
 4–6 h/wk walking only521/106,0284900.89 (0.80–0.98)0.91 (0.82–1.01)
 ≥7 h/wk walking only260/56,5304400.82 (0.72–0.94)0.86 (0.75–0.98)
 ≤3 h/wk walking plusd1,147/215,2295300.97 (0.90–1.05)0.95 (0.88–1.03)
 4–6 h/wk walking plusd513/93,7705410.99 (0.90–1.10)1.00 (0.90–1.10)
 ≥7 h/wk walking plusd240/52,6644470.82 (0.71–0.94)0.83 (0.73–0.96)
 Active nonwalkersg111/20,4465451.01 (0.83–1.22)0.97 (0.80–1.18)
Sitting h/de
 <32,388/474,9365021.001.00
 3–51,721/321,1325311.06 (1.00–1.13)1.03 (0.97–1.10)
 ≥6572/101,2025461.10 (1.01–1.21)1.05 (0.96–1.16)
Ptrend = 0.20 (active women only; Ptrend = 0.26)c,e,f
  • aStandardized to the age-distribution of the Nutrition Cohort women.

  • bAge-adjusted.

  • cAdjusted for age, race, education, BMI (kg/m2), weight change, alcohol use, smoking status, PMH use, number of live births, age at first live birth, age at menopause, family history of breast cancer, breast cysts, hysterectomy, oophorectomy, and mammogram within last year.

  • dWalking in addition to other recreational activities.

  • eAlso adjusted for MET expenditure from total recreational activities.

  • fWomen reporting no physical activity (“None”) excluded from Ptrend calculations.

  • gWomen who engage in recreational activities other than walking.