Table 6.

Sedentary Time and Breast Cancer Incidence (1995–2013) by Body Composition Measurements

Total sitting time	Cases/Person-years	HR (95% CI)a	Cases/Person-years	HR (95% CI)a	Cases/Person-years	HR (95% CI)a	Pintb
	Current BMI <25 kg/m2		Current BMI 25–<30 kg/m2		Current BMI ≥30 kg/m2
<5 hours/day	113/42,852	Reference	137/48,103	Reference	115/47,658	Reference	0.22
5–<7 hours/day	192/84,180	0.99 (0.75, 1.29)	243/91,067	1.12 (0.88, 1.44)	308/101,911	1.31 (1.01, 1.70)
7–<10 hours/day	131/55,605	0.89 (0.66, 1.20)	217/70,327	1.38 (1.07, 1.78)	286/96,175	1.33 (1.02, 1.73)
≥10 hours/day	44/16,829	1.36 (0.93, 1.98)	75/22,831	1.49 (1.07, 2.08)	109/36,866	1.44 (1.06, 1.97)
		P-trend=0.03		P-trend=0.002		P-trend=0.54
	BMI at 18 years <20 kg/m2		BMI at 18 years 20–<25 kg/m2		BMI at 18 years ≥25 kg/m2
<5 hours/day	181/58,409	Reference	155/61,992	Reference	27/17,310	Reference	0.28
5–<7 hours/day	346/113,918	1.18 (0.95, 1.46)	324/125,478	1.09 (0.87, 1.37)	66/36,174	0.94 (0.56, 1.57)
7–<10 hours/day	278/87,307	1.13 (0.90, 1.41)	291/99,300	1.34 (1.06, 1.69)	63/34,031	0.96 (0.57, 1.63)
≥10 hours/day	93/29,302	1.18 (0.88, 1.58)	104/33,407	1.60 (1.20, 2.13)	27/12,294	1.30 (0.70, 2.39)
		P-trend=0.44		P-trend<0.001		P-trend=0.34
	Adult weight gain <10 kg		Adult weight gain 10–<20kg		Adult weight gain ≥20 kg
<5 hours/day	74/34,943	Reference	103/39,389	Reference	187/63,720	Reference	0.26
5–<7 hours/day	119/66,592	0.85 (0.61, 1.18)	213/78,132	1.35 (1.02, 1.79)	405/131,498	1.12 (0.91, 1.38)
7–<10 hours/day	79/44,267	0.89 (0.61, 1.28)	168/58,618	1.47 (1.10, 1.98)	385/118,239	1.19 (0.97, 1.47)
≥10 hours/day	30/14,072	1.21 (0.75, 1.96)	55/18,296	1.85 (1.27, 2.69)	139/43,766	1.27 (0.98, 1.64)
		P-trend=0.05		P-trend=0.001		P-trend=0.74
	Waist-Hip Ratio <0.75		Waist-Hip Ratio 0.75–<0.85		Waist-Hip Ratio ≥0.85
<5 hours/day	84/34,707	Reference	114/39,491	Reference	69/23,305	Reference	0.65
5–<7 hours/day	188/72,748	1.16 (0.86, 1.56)	299/78,679	1.20 (0.91, 1.58)	103/42,160	0.79 (0.55, 1.14)
7–<10 hours/day	127/51,122	1.01 (0.72, 1.40)	197/65,431	1.24 (0.94, 1.65)	101/37,556	1.00 (0.69, 1.44)
≥10 hours/day	43/15,686	1.42 (0.94, 2.16)	70/21,767	1.42 (0.99, 2.03)	45/14,829	1.19 (0.77, 1.85)
		P-trend=0.28		P-trend=0.06		P-trend=0.37
	Waist Circumference <80 cm		Waist Circumference 80–88 cm		Waist Circumference >88 cm
<5 hours/day	123/52,629	Reference	79/23,433	Reference	74/24,024	Reference	0.37
5–<7 hours/day	264/109,666	1.22 (0.94, 1.58)	133/41,285	0.97 (0.70, 1.35)	137/47,466	1.02 (0.72, 1.43)
7–<10 hours/day	199/78,057	1.30 (0.99, 1.71)	113/36,240	0.88 (0.63, 1.24)	126/44,218	1.01 (0.72, 1.44)
≥10 hours/day	68/23,988	1.56 (1.10, 2.23)	37/12,262	1.12 (0.72, 1.74)	60/17,638	1.41 (0.94, 2.10)
		P-trend=0.15		P-trend=0.96		P-trend=0.01

Abbreviations: BMI, body mass index; cm, centimeters; CI, confidence interval; HR, hazard ratio; kg, kilograms; m, meters; P_int, P-interaction.

^aCox proportional hazards regression, with values updated using Anderson-Gill method, adjusted for: age (continuous), geographic region of residence (Northeast, South, Midwest, West, other), education (≤12, 13–15, ≥ 16 years), recreational physical activity (low, moderate, high), caloric intake (continuous), parity (0, 1–2, ≥3), age at menarche (≤11, 12–13, ≥14), menopausal hormone use (premenopausal, postmenopausal-never, postmenopausal-<5 years, postmenopausal- ≥ 5 years), oral contraceptive use (never, 0.5–5, ≥5 years), family history of breast cancer (yes/no), mammogram (ever, never), smoking (never, former, current-<15 per day, current-≥15 per day).

^bLikelihood ratio chi-square test.