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

Table 4 Relative risk (RR) and 95% confidence intervals (CI) for the association of light physical activity during four periods of life with breast cancer incidence: 118,899 postmenopausal women in the NIH-AARP Diet and Health Study

Light activity	No. cancers* n = 4287	RR^†	95% CI	RR^††	95% CI		RR^§	95% CI		RR^£	95% CI
Ages 15-18 years
Never/Rarely	358	1.00 (ref.)		1.00 (ref.)			1.00 (ref.)			1.00 (ref.)
<1 hour/week	344	1.09	0.94, 1.27	1.09	0.94	1.26	1.07	0.92	1.24	1.09	0.94	1.26
1-3 hours/week	974	1.06	0.94, 1.20	1.05	0.93	1.19	1.04	0.92	1.18	1.05	0.93	1.18
4-7 hours/week	982	1.08	0.96, 1.22	1.08	0.95	1.22	1.07	0.95	1.22	1.07	0.95	1.21
>7 hours/week	1553	1.03	0.92, 1.16	1.05	0.94	1.18	1.05	0.93	1.19	1.04	0.93	1.17
Ages 19-29 years
Never/Rarely	199	1.00 (ref.)		1.00 (ref.)			1.00 (ref.)			1.00 (ref.)
<1 hour/week	249	1.18	0.98, 1.42	1.16	0.97	1.40	1.15	0.95	1.38	1.16	0.96	1.40
1-3 hours/week	793	1.14	0.98, 1.34	1.11	0.95	1.30	1.10	0.94	1.29	1.11	0.95	1.30
4-7 hours/week	1036	1.13	0.97, 1.32	1.12	0.96	1.30	1.11	0.95	1.30	1.11	0.96	1.30
>7 hours/week	1940	1.05	0.91, 1.21	1.07	0.93	1.24	1.07	0.92	1.25	1.07	0.92	1.24
Ages 35-39 years
Never/Rarely	171	1.00 (ref.)		1.00 (ref.)			1.00 (ref.)			1.00 (ref.)
<1 hour/week	238	1.19	0.98, 1.44	1.17	0.96	1.42	1.14	0.94	1.40	1.16	0.95	1.41
1-3 hours/week	811	1.19	1.01, 1.41	1.15	0.98	1.36	1.15	0.97	1.36	1.15	0.98	1.36
4-7 hours/week	1036	1.08	0.92, 1.27	1.05	0.89	1.24	1.04	0.88	1.23	1.05	0.91	1.24
>7 hours/week	1952	1.05	0.90, 1.23	1.06	0.90	1.24	1.06	0.90	1.24	1.06	0.91	1.24
Past 10 years
Never/Rarely	183	1.00 (ref.)		1.00 (ref.)			1.00 (ref.)			1.00 (ref.)
<1 hour/week	266	1.23	1.02, 1.48	1.21	1.00	1.46	1.19	0.98	1.44	1.21	1.00	1.46
1-3 hours/week	890	1.13	0.96, 1.32	1.08	0.92	1.27	1.10	0.93	1.29	1.09	0.93	1.28
4-7 hours/week	1264	1.20	1.02, 1.40	1.14	0.98	1.34	1.19	1.01	1.39	1.16	0.99	1.36
>7 hours/week	1634	1.04	0.89, 1.21	1.01	0.87	1.18	1.09	0.92	1.28	1.04	0.89	1.21

* Number of cancer cases may not add up to total (n = 4287) due to missing physical activity values
† Relative risks adjusted for age (continuous)
†† Relative risks adjusted for: age (continuous); race/ethnicity (white, black, Hispanic, Asian/Pacific Islander/American Indian); education level (<12 years or high school equivalent, 12 years or high school equivalent, post-high school vocational or technical training, some college, college graduate, post-graduate); smoking status (non-smoker, former, current); alcohol intake (grams/day, quintiles adjusted for total energy intake); family history of breast cancer (no, yes); age at menarche (<13, 13-14, ≥ 15 years); age at first birth (nulliparous, <20, 20-24, 25-29, 30+ years); parity (number of children: 0, 1-2, 3 or more); age at menopause (<40, 40-44, 45-49, 50-54, ≥ 55 years); menopausal hormone use (never, ever)
§Relative risks additionally adjusted for frequency of other type of physical activity (either light or moderate-to-vigorous) during that same time period
£ Relative risks additionally adjusted for body mass index (BMI: <25.0, 25.0-29.9, 30.0-34.9, ≥ 35.0 kg/m²)

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