Table 4.

Multivariable adjusted¹ OR and 95% CI for invasive breast cancer defined by HER2 status with recreational physical activity in specific time periods or age periods

Average exercise activity (annual MET h/week)	No. of participants			OR (95% CI)
	Controls	HER2− cases	HER2+ cases	HER2− cases versus controls	HER2+ cases versus controls	HER2− versus HER2+
First 10 years after menarche
Inactive2	504	260	49	Referent	Referent	Referent
≤2.2	97	44	5	0.82 (0.55–1.22)	0.54 (0.21–1.42)	1.54 (0.57–4.19)
2.3–6.6	186	94	30	0.85 (0.63–1.15)	1.69 (1.02–2.80)	0.55 (0.32–0.94)
6.7–15.1	241	120	28	0.84 (0.64–1.11)	1.25 (0.75–2.08)	0.67 (0.39–1.16)
≥15.2	412	187	43	0.77 (0.60–0.98)	1.10 (0.70–1.74)	0.67 (0.41–1.08)
Trend P-value				0.05	0.25	0.02
Homogeneity of trends for case–control comparison				P = 0.03
Exercise only in other time period(s)	572	274	61	0.87 (0.70–1.08)	1.17 (0.78–1.75)	0.74 (0.48–1.14)
Ages 10–19 years
Inactive3	500	258	49	Referent	Referent	Referent
≤2.2	76	49	9	1.13 (0.75–1.68)	1.22 (0.57–2.64)	0.95 (0.42–2.12)
2.3–6.6	195	83	22	0.71 (0.52–0.97)	1.19 (0.68–2.07)	0.57 (0.31–1.02)
6.7–15.1	221	109	19	0.80 (0.60–1.07)	0.87 (0.49–1.55)	0.91 (0.50–1.66)
≥15.2	409	187	45	0.78 (0.61–1.00)	1.14 (0.73–1.80)	0.67 (0.41–1.08)
Trend P-value				0.02	0.53	0.05
Homogeneity of trends for case–control comparison				P = 0.06
Exercise only in other age group(s)	611	293	72	0.87 (0.71–1.08)	1.27 (0.85–1.87)	0.70 (0.46–1.06)
Ages 20–34 years
Inactive3	500	258	49	Referent	Referent	Referent
≤2.2	164	76	10	0.82 (0.59–1.13)	0.63 (0.31–1.29)	1.43 (0.67–3.04)
2.3–6.6	225	131	33	1.03 (0.78–1.36)	1.54 (0.95–2.52)	0.66 (0.39–1.11)
6.7–15.1	286	148	29	0.89 (0.68–1.16)	1.02 (0.61–1.69)	0.83 (0.49–1.42)
≥15.2	365	151	33	0.72 (0.56–0.93)	0.92 (0.57–1.50)	0.76 (0.45–1.27)
Trend P-value				0.03	0.85	0.11
Homogeneity of trends for case–control comparison				P = 0.20
Exercise only in other age group(s)	472	215	62	0.81 (0.64-1.02)	1.44 (0.95-2.17)	0.56 (0.36-0.87)
10 years before reference date
Inactive3	500	258	49	Referent	Referent	Referent
≤2.2	188	90	19	0.89 (0.66–1.21)	1.06 (0.60–1.86)	0.89 (0.48–1.62)
2.3–6.6	277	140	32	0.88 (0.67–1.14)	1.26 (0.78–2.05)	0.70 (0.42–1.17)
6.7–15.1	333	172	42	0.90 (0.70–1.16)	1.31 (0.84–2.06)	0.69 (0.43–1.12)
≥15.2	441	200	45	0.78 (0.62–0.99)	1.09 (0.70–1.71)	0.67 (0.42–1.09)
Trend P-value				0.06	0.55	0.07
Homogeneity of trends for case–control comparison				P = 0.12
Exercise only in other time period(s)	273	119	29	0.74 (0.56–0.98)	1.11 (0.67–1.83)	0.69 (0.40–1.17)

OR, odds ratio; CI, confidence interval. HER2, human epidermal growth factor receptor 2.

¹Adjusted for study site, race, education, age, family history of breast cancer, age at menarche, parity, a four-category variable combining menopausal status and hormone therapy use, body mass index, and the duration of oral contraceptive use.

²Inactive between age at menarche and reference date.

³Inactive between age 10 years and reference date.