7 hours/week of moderate-to-vigorous activity during the past 10 years was associated with 16% reduced risk of postmenopausal breast cancer (RR:0.84; 95%CI:0.76,0.93) compared with inactivity. The association remained statistically significant after adjustment for BMI (RR:0.87; 95%CI:0.78,0.96). Neither moderate-to-vigorous activity during other periods of life nor light intensity activity during any period of life was related to breast cancer risk, and associations did not vary by tumor characteristics. Conclusion A high level of recent, but not historical, physical activity of moderate-to-vigorous intensity is associated with reduced postmenopausal breast cancer risk. More precise recall of recent physical activity than activity in the distant past is one possible explanation for our findings."/>
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Table 2 Characteristics of the study population by light and moderate-to-vigorous intensity physical activity during two periods of life: 118,899 postmenopausal women in the NIH-AARP Diet and Health Study

From: Intensity and timing of physical activity in relation to postmenopausal breast cancer risk: the prospective NIH-AARP Diet and Health Study

Light activity Total Ages 35-39 years Past 10 years
   Never/Rarely <1 hr/wk 1-3 hrs/wk 4-7 hrs/wk >7 hrs/wk Never/Rarely <1 hr/wk 1-3 hrs/wk 4-7 hrs/wk >7 hrs/wk
Participants, No. (%) 118899 5189 (4) 6121 (5) 20710 (17) 29018 (24) 55602 (47) 5789 (5) 6811 (6) 24450 (21) 32432 (27) 47827 (40)
Age at baseline (yrs) 62.9 62.6 62.2 62.4 62.6 63.3 62.5 62.3 62.4 62.9 63.2
BMI, current* (kg/m2) 26.7 27.0 27.3 26.8 26.7 26.6 28.6 28.4 27.4 26.6 26.0
BMI at age 18* (kg/m2) 20.9 21.1 21.1 21.0 20.9 20.8 21.3 21.1 21.0 20.8 20.8
Caucasian (%) 91.2 85.3 85.8 89.5 91.8 93.1 84.9 85.0 90.0 92.3 93.1
College education (%) 31.5 31.8 33.6 35.0 34.3 28.9 27.5 29.8 34.0 33.8 29.6
Family history of breast cancer (%) 13.7 13.1 13.8 13.4 13.5 13.9 13.6 13.3 13.4 13.6 13.8
Current smoker (%) 13.4 12.6 12.8 13.3 13.1 13.7 16.7 15.1 13.7 12.9 12.9
Ever MHT use (%) 61.7 59.0 58.7 61.6 62.5 62.1 56.9 58.3 61.8 62.8 62.0
Age at menarche (yrs) 12.50 12.51 12.48 12.48 12.48 12.51 12.48 12.47 12.47 12.48 12.53
Age at first birth (yrs) 22.98 22.98 23.33 23.30 23.23 22.73 22.75 23.04 23.20 23.14 22.81
Parity (no. of children) 2.01 1.87 1.79 1.77 1.90 2.19 1.92 1.88 1.89 1.98 2.11
Age at menopause(yrs) 47.02 47.01 47.31 47.32 47.34 47.24 46.59 47.00 47.20 47.43 47.34
Alcohol intake (g/d) 6.2 6.0 6.1 6.3 6.4 6.1 6.1 5.5 6.1 6.3 6.2
Moderate-to-vigorous activity   Ages 35-39 years Past 10 years
   Never/Rarely <1 hr/wk 1-3 hrs/wk 4-7 hrs/wk >7 hrs/wk Never/Rarely <1 hr/wk 1-3 hrs/wk 4-7 hrs/wk >7 hrs/wk
Participants, No. (%) 118899 10868 (9) 10507 (9) 26715 (23) 31560 (27) 37477 (32) 17028 (14) 12498 (11) 29927 (25) 30231 (25) 28214 (24)
Age at baseline (yrs) 62.9 62.8 62.5 62.5 62.7 63.4 62.9 62.5 62.7 62.9 63.1
BMI, current* (kg/m2) 26.7 27.6 27.3 26.8 26.5 26.4 28.7 28.0 26.9 26.0 25.4
BMI at age 18* (kg/m2) 20.9 21.3 21.0 20.9 20.8 20.7 21.2 21.0 20.8 20.8 20.7
Caucasian (%) 91.2 88.0 89.1 90.9 92.6 92.6 88.7 89.7 91.4 92.7 92.4
College education (%) 31.5 33.2 35.8 35.7 33.0 26.4 30.3 31.8 33.7 33.7 27.9
Family history of breast cancer (%) 13.7 13.0 13.4 13.7 13.6 14.0 13.3 13.9 13.4 14.1 13.6
Current smoker (%) 13.4 12.0 12.3 12.5 13.3 14.8 15.5 14.3 13.6 12.6 12.5
Ever MHT use (%) 61.7 56.7 60.1 63.0 63.3 61.8 57.8 60.8 62.1 64.1 61.6
Age at menarche (yrs) 12.50 12.38 12.48 12.48 12.49 12.55 12.40 12.46 12.48 12.52 12.56
Age at first birth (yrs) 22.98 23.39 23.40 23.25 23.02 22.60 23.06 23.06 23.07 23.06 22.76
Parity (no. of children) 2.01 1.74 1.81 1.89 2.02 2.22 1.88 1.95 1.99 2.04 2.09
Age at menopause(yrs) 47.02 47.39 47.42 47.42 47.33 47.05 46.94 47.17 47.34 47.40 47.26
Alcohol intake (g/d) 6.2 5.7 5.9 6.3 6.5 6.2 5.8 5.8 6.1 6.4 6.5
  1. *BMI: body mass index.
  2. †Family history of breast cancer in a first-degree female relative.
  3. ‡MHT: menopausal hormone therapy.