Table 5.

ORs and 95% CIs for an association between low-, moderate-, and high-intensity outdoor activity episodes at ages 10 to 19, 20 to 29, and 45 to 54, and breast cancer in cases and controls

Cases (%)Controls (%)OR* (95% CI)OR (95% CI)
Low-intensity outdoor activity
    Ages 10-19
        <1285 (31)250 (23)1.001.00
        1-98215 (23)259 (24)0.76 (0.59-0.97)0.80 (0.61-1.04)
        99-313216 (23)287 (26)0.69 (0.54-0.88)0.76 (0.58-0.99)
        314+209 (23)295 (27)0.65 (0.51-0.83)0.69 (0.53-0.91)
    Ages 20-29
        <1295 (32)302 (27)1.001.00
        1-80188 (20)237 (21)0.83 (0.65-1.07)0.88 (0.68-1.15)
        81-240268 (29)337 (31)0.83 (0.66-1.04)0.90 (0.70-1.14)
        241+179 (19)229 (21)0.81 (0.63-1.05)0.85 (0.65-1.11)
    Ages 45-54
        <6493 (23)108 (23)1.001.00
        64-143100 (25)115 (25)1.01 (0.69-1.49)1.04 (0.70-1.56)
        144-28797 (24)116 (25)0.97 (0.66-1.43)0.90 (0.60-1.36)
        288+114 (28)124 (27)1.07 (0.73-1.56)1.01 (0.68-1.50)
Moderate-intensity outdoor activity
    Ages 10-19
        <295263 (28)246 (22)1.001.00
        295-672226 (24)297 (27)0.72 (0.56-0.92)0.70 (0.54-0.90)
        673-840253 (27)272 (25)0.87 (0.68-1.12)0.87 (0.67-1.12)
        841+187 (20)287 (26)0.60 (0.47-0.78)0.58 (0.44-0.76)
    Ages 20-29
        <225275 (29)236 (21)1.001.00
        225-540234 (25)292 (26)0.69 (0.54-0.88)0.74 (0.57-0.95)
        541-840237 (25)304 (27)0.66 (0.52-0.85)0.68 (0.53-0.88)
        841+191 (20)280 (25)0.57 (0.44-0.73)0.59 (0.45-0.77)
    Ages 45-54
        <24094 (14)116 (15)1.001.00
        240-504182 (27)195 (25)1.14 (0.81-1.60)1.10 (0.77-1.56)
        504-839144 (21)170 (22)1.03 (0.73-1.47)0.98 (0.68-1.41)
        840+260 (38)302 (39)1.04 (0.75-1.44)0.99 (0.70-1.38)
High-intensity outdoor activity
    Ages 10-19
        <141290 (31)222 (20)1.001.00
        141-416223 (24)285 (26)0.61 (0.48-0.79)0.62 (0.47-0.80)
        417-840216 (23)300 (27)0.56 (0.44-0.72)0.57 (0.44-0.74)
        841+205 (22)295 (27)0.55 (0.43-0.7100.59 (0.45-0.77)
    Ages 20-29
        <1295 (32)257 (23)1.001.00
        1-120229 (24)291 (26)0.71 (0.56-0.90)0.75 (0.59-0.97)
        121-324200 (21)261 (24)0.68 (0.53-0.88)0.75 (0.57-0.97)
        325+211 (23)297 (27)0.65 (0.51-0.83)0.70 (0.54-0.90)
    Ages 45-54
        <4867 (15)72 (13)1.001.00
        48-11980 (18)87 (16)0.99 (0.63-1.56)0.96 (0.60-1.53)
        120-269129 (29)163 (30)0.84 (0.56-1.27)0.77 (0.51-1.18)
        270+174 (39)224 (41)0.83 (0.56-1.22)0.79 (0.53-1.18)
  • * ORs with 95% CIs adjusted for reference age.

  • ORs with 95% CIs adjusted for reference age, ethnicity, family history in first-degree relatives, ever breast-fed, education, age menarche, and age at first birth.

  • Number of outdoor activity episodes derived from reported outdoor activities done for at least 30 min between 9 a.m. and 5 p.m. at least once per month during June, July, and August along with frequency (days per week or month) and duration (number of years) and classified as low, moderate, or high intensity.