Long-term Exposure to Fine Particulate Matter and Breast Cancer Incidence in the Danish Nurse Cohort Study

Zorana Jovanovic Andersen; Line Ravnskjær; Klaus Kaae Andersen; Steffen Loft; Jørgen Brandt; Thomas Becker; Matthias Ketzel; Ole Hertel; Elsebeth Lynge; Elvira Vaclavik Bräuner

doi:10.1158/1055-9965.EPI-16-0578

DOI: 10.1158/1055-9965.EPI-16-0578 Published March 2017

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Tables

Table 1.

Characteristics of the nurses from the DNC at baseline in 1993 or 1999, by incident breast cancer status at follow-up

	Total	Breast cancer	No breast cancer
	n = 22,877	n = 1,145	n = 21,732
Age, mean (SD)	52.9 (7.8)	53.2 (7.3)	52.9 (7.8)
Premenopausal, n (%)	11,579 (51.0)	583 (51.5)	10,996 (51.0)
Postmenopausal, n (%)	11,120 (49.0)	548 (48.5)	10,572 (49.0)
Menarche ≤ 12, n (%)	5,477 (24.1)	290 (25.6)	5,187 (24.0)
Menarche > 12, n (%)	17,222 (75.9)	841 (74.4)	16,381 (76.0)
BMI, mean (SD)	23.7 (3.5)	23.8 (3.5)	23.7 (3.5)
Underweight (<18.5 kg/m²), n (%)	532 (2.3)	22 (1.9)	510 (2.4)
Normal (18.5–25 kg/m²), n (%)	15,698 (69.2)	801 (70.8)	14,987 (69.1)
Overweight (25–30 kg/m²), n (%)	5,167 (22.8)	239 (21.1)	4,928 (22.8)
Obese (≥30 kg/m²), n (%)	1,302 (5.7)	69 (6.1)	1,233 (5.7)
Never smoked, n (%)	7,956 (35.1)	359 (31.7)	7,597 (35.2)
Previously smoked, n (%)	6,922 (30.5)	330 (29.2)	6,592 (30.6)
Current smoker, n (%)	7,821 (34.5)	442 (39.1)	7,379 (34.2)
Smoking intensity (g/day), mean (SD)	7.8 (9.2)	8.4 (8.8)	7.8 (9.2)
Never consumed alcohol, n (%)	3,894 (17.2)	195 (17.2)	3,699 (17.2)
Alcohol use in drinkers (g/week), mean (SD)	112.5 (127.6)	120.7 (119.8)	112.1 (127.9)
Low physical activity, n (%)	1,496 (6.6)	71 (6.3)	1,425 (6.6)
Medium physical activity, n (%)	6,132 (27.0)	299 (26.4)	5,833 (27.0)
High physical activity, n (%)	15,071 (66.4)	761 (67.3)	14,310 (66.3)
Nulliparous, n (%)	3,163 (10.3)	180 (15.9)	2,983 (13.8)
Gave birth to 1 child, n (%)	2,680 (11.8)	140 (12.4)	2,540 (11.8)
Gave birth to 2 children, n (%)	9,648 (42.5)	467 (41.3)	9,181 (42.6)
Gave birth to 3 children, n (%)	5,499 (24.2)	271 (24.0)	5,228 (24.2)
Gave birth to 4 children or more, n (%)	1,709 (7.5)	73 (6.5)	1,636 (7.6)
Age at first birth 15–24 years, n (%)	8,123 (35.8)	383 (33.9)	7,740 (35.9)
Age at first birth 25–29 years, n (%)	8,350 (36.8)	384 (34.0)	7,966 (36.9)
Age at first birth 30 years, n (%)	3,065 (13.5)	184 (16.3)	2,881 (13.4)
Never used HT, n (%)	16,600 (73.1)	743 (65.7)	15,857 (73.5)
Previously used HT, n (%)	2,193 (9.7)	99 (8.8)	2,094 (9.7)
Current user of HT, n (%)	3,906 (17.2)	289 (25.6)	3,617 (16.8)
Never used OC, n (%)	9,202 (40.5)	475 (42.0)	8,727 (40.5)
Ever used OC, n (%)	13,497 (59.5)	656 (58.0)	12,841 (59.5)
Rural, n (%)	9,784 (43.1)	514 (45.4)	9,270 (43.0)
Provincial, n (%)	3,368 (14.8)	163 (14.4)	3,205 (14.9)
Urban, n (%)	9,547 (42.1)	454 (40.1)	9,093 (42.2)
Baseline annual PM_2.5 (μg/m³), mean (SD)	19.7 (3.5)	20.2 (3.5)	19.6 (3.6)
Baseline annual PM₁₀ (μg/m³), mean (SD)	23.5 (3.9)	24.1 (3.8)	23.5 (3.9)
Baseline annual NO₂ (μg/m³), mean (SD)	12.5 (8.1)	12.7 (8.0)	12.5 (8.1)

Abbreviation: OC, oral contraceptives.

Table 2.

Association between air pollution and breast cancer among the 22,877 nurses from DNC

		Model 1^a	Model 2^b	Model 3^c
	Unit	HR (95% CI)	HR (95% CI)	HR (95% CI)
3-year mean
PM_2.5	3.3 μg/m³	1.03 (0.94–1.13)	1.02 (0.93–1.12)	1.00 (0.91–1.09)
PM₁₀	2.9 μg/m³	1.04 (0.95–1.14)	1.03 (0.95–1.12)	1.02 (0.94–1.11)
NO₂	7.4 μg/m³	1.03 (0.97–1.10)	1.02 (0.96–1.08)	1.00 (0.94–1.07)

↵^aAdjusted for age.
↵^bModel 1 additionally adjusted for smoking (status and intensity), alcohol use, BMI, and physical activity.
↵^cModel 3 also adjusted for parity, age at first birth, age at menarche, hormone therapy use, oral contraceptive use, and menopausal status.