Table 3.

Baseline characteristics associated with physical activity in the JACC study

CharacteristicsTime spent exercising <1 h/wk
Time spent exercising ≥1 h/wk
Time spent walking per day
Time spent walking per day
<1 h≥1 h<1 h≥1 h
Number, n (row %)11,864 (39.3)10,824 (35.9)3,414 (11.3)4,055 (13.4)
BMI, mean ± SD (kg/m2)22.8 ± 3.222.7 ± 3.022.8 ± 3.022.7 ± 2.9
Age at baseline, mean ± SD, y57.5 ± 10.356.8 ± 9.658.5 ± 10.359.2 ± 10.4
Age at menarche, mean ± SD, y14.8 ± 1.814.9 ± 1.814.8 ± 1.814.9 ± 1.8
Age at birth of first child, mean ± SD, y25.2 ± 3.325.0 ± 3.325.1 ± 3.224.9 ± 3.1
Age at menopause, mean ± SD, y48.7 ± 4.848.6 ± 4.648.8 ± 4.748.9 ± 4.5
Age of the end of education, mean ± SD, y16.6 ± 2.116.5 ± 2.116.9 ± 2.216.7 ± 2.1
Postmenopausal, n (%)8,946 (75.4)8,176 (75.5)2,657 (77.8)3,225 (79.5)
Nulliparous, n (%)612 (5.2)387 (3.6)142 (4.2)163 (4.0)
Not married, n (%)223 (2.0)120 (1.2)65 (2.1)42 (1.1)
Exogenous female hormone use, n (%)580 (5.4)474 (4.8)191 (6.2)207 (5.7)
Family history of breast cancer,* n (%)191 (1.6)159 (1.5)63 (1.9)65 (1.6)
Current smoker, n (%)606 (5.6)556 (5.7)133 (4.3)183 (5.0)
Current drinker, n (%)2,594 (23.1)2,447 (24.0)906 (27.9)1,122 (29.4)
  • NOTE: Mean (SD) or %, calculated for participants with complete physical activity data.

  • * In a first-degree relative.