Prospective study of physical activity and risk of postmenopausal breast cancer

Breast Cancer Research

Table 5 Relative risk of oestrogen receptor positive (ER+) breast cancer and oestrogen receptor negative (ER-) breast cancer in relation to vigorous physical activity among US women in the Breast Cancer Detection Demonstration Project (BCDDP; 1987 to 1998)*

Variable	No. of Cases	Category of vigorous physical activity					p
		1	2	3	4	5
ER/PR receptor status
ER+	706	1.0	0.94	0.93	0.93	0.91 (0.72 to 1.15)	0.42
PR+	588	1.0	1.13	0.97	1.03	0.93 (0.72 to 1.22)	0.54
ER+/PR+	555	1.0	1.08	0.97	1.02	0.93 (0.71 to 1.23)	0.61
ER+/PR-	115	1.0	2.40	0.89	0.97	0.49 (0.10 to 2.32)	0.22
ER-	161	1.0	1.36	0.79	1.02	0.74 (0.44 to 1.27)	0.22
PR-	248	1.0	0.77	0.74	0.80	0.77 (0.52 to 1.15)	0.23
ER-/PR+	29	1.0	0.55	0.60	0.56	0.81 (0.46 to 1.41)	0.43
ER-/PR-	126	1.0	1.02	0.80	1.06	0.76 (0.42 to 1.35)	0.43
Combination of ER receptor status and BMI
ER+, BMI < 25.0 kg/m²	417	1.0	0.79	0.87	0.95	0.75 (0.54 to 1.03)	0.15
ER+, BMI ≥ 25.0 kg/m²	289	1.0	1.20	1.01	0.86	1.19 (0.83 to 1.69)	0.60
Combination of ER/PR receptor status and BMI
ER+/PR+, BMI < 25.0 kg/m²	327	1.0	0.94	0.93	1.09	0.81 (0.56 to 1.17)	0.43
ER+/PR+, BMI ≥ 25.0 kg/m²	228	1.0	1.29	1.02	0.89	1.14 (0.76 to 1.71)	0.81

BMI = body mass index; CI = confidence interval; ER = oestrogen receptor; PR = progesterone receptor; RR = relative risk. The multivariate model included the following: age at baseline (continuous), family history of breast cancer (any first or second degree relative; yes, no or unknown), history of benign breast disease (any benign breast disease prior to study baseline, including during the screening stages; yes or no), breast cancer screening history (women who had undergone a breast biopsy as part of the BCDDP screening but lacked evidence of malignant disease, women who were recommended for surgical consultation as part of the BCDDP but for whom the procedure was not performed, or women who represented a random sample of BCDDP participants who had no surgery or recommendation for surgical consultation during BCDDP screening), height (continuous), age at menarche (≤ 11, 12, 13 or 14+ years of age), age at menopause (age at which menstrual period stopped for at least three continuous months; <47 or 47+ years of age), age at first live birth (continuous), history of oral contraceptive use (yes or no), menopausal hormone therapy (ever or never), education attainment (less than or equal to high school or greater than high school), cigarette smoking (ever or never), and intakes of energy-adjusted dietary fat (continuous) and alcohol (continuous). Within each stratum, the group with lowest vigorous physical activity served as the reference group.

ISSN: 1465-542X