Sex Hormones, Risk Factors, and Risk of Estrogen Receptor–Positive Breast Cancer in Older Women: A Long-term Prospective Study

DOI: 10.1158/1055-9965.EPI-04-0375 Published May 2005

Article Figures & Data

Table 1.

Baseline characteristics of the 7,676 subjects

Characteristic	Mean (SD)			P
Characteristic		Invasive ER+ breast cancer (n = 208)	No breast cancer (n = 7,468)	P
Age (y)	70.3 (4.3)	71.9 (5.4)	<0.001*
Education (y)	12.9 (2.7)	12.4 (2.8)	0.01*
Weight (kg)	70.9 (12.8)	67.3 (12.6)	<0.001*
Age at menarche (y)	12.9 (1.5)	13.1 (1.5)	0.22
Age at last natural menses (y)	47.7 (5.8)	47.0 (6.3)	0.13
Years of reproductive life (y)	34.7 (6.1)	34.0 (6.5)	0.16
Age at first childbirth (y)	25.4 (5.2)	25.3 (4.9)	0.74
No. live births	2.8 (1.7)	2.7 (1.6)	0.61
No. children breast-fed	1.6 (1.6)	1.6 (1.6)	0.60
Underwent surgical menopause (%)	11.4	9.8	0.46
Past use of estrogen therapy (%)	35.0	31.8	0.33
Family history of breast cancer^† (%)	16.2	14.5	0.51
Current smoker (%)	11.1	10.0	0.62
Alcoholic drinks per week	2.4 (4.8)	1.9 (4.1)	0.07
Physical activity (total weekly kcal in past year)	1,711 (1,792)	1,552 (1,627)	0.17
Takes walks for exercise (%)	47.6	49.1	0.66
Distal radius BMD (g/cm²)	0.38 (0.08)	0.35 (0.08)	<0.001*
Lumbar spine BMD (g/cm²)	0.88 (0.15)	0.84 (0.16)	0.01*
Total hip BMD (g/cm²)	0.79 (0.12)	0.75 (0.13)	<0.001*

Table 2.

Age-adjusted associations of risk factors with ER+ invasive breast cancer in the whole cohort

Variable (comparison)	Relative risk (95 % CI)
No. cases*	196
Education > 16 y (≤16 y)	1.7 (1.1-2.5)
Weight (per 10 kg)	1.2 (1.1-1.3)
Distal radius BMD^†	1.3 (1.1-1.5)
Family history of breast cancer^‡	1.2 (0.8-1.8)
Current smoker (noncurrent)	1.1 (0.7-1.7)
Surgical menopause (natural)	1.2 (0.8-1.9)
Takes walks for exercise (none)	0.8 (0.6-1.1)
Alcoholic drinks/wk (per four drinks)	1.1 (1.0-1.3)
Exercise (kcal/wk; per 1,631 kcal)	1.0 (0.9-1.2)
Age at last natural menses (per 6.3 y)	1.1 (0.9-1.3)
Age at menarche (per 1.5 y)	0.9 (0.8-1.1)
Years of reproductive life (per 6.5 y)	1.1 (0.9-1.3)
Age at first child born (per 5 y)	1.0 (0.9-1.2)
Births (per 1.6 live births)	1.0 (0.8-1.1)
Children breast-fed (per 1.6 children)	1.0 (0.9-1.2)

Abbreviation: BMD, bone mineral density.
↵* The number of cases in the whole cohort (208) is greater than in the case-cohort analyses because 12 participants did not have sufficient blood for analyses of sex hormone levels in the case-cohort study.
↵† Per SD increase in BMD.
↵‡ At least one sister or mother with breast cancer.

Table 3.

Serum sex hormone concentrations and other risk factors for ER+ breast cancer in the nested case-cohort study

Abbreviation: BMD, bone mineral density.
↵* Adjusted for weight, education, radius BMD, testosterone, and estradiol. P_trend for estradiol = 0.06 and P_trend for testosterone < 0.001.
↵† Per SD increase.
↵‡ Quintiles for testosterone (pmol/L): 1st, <381; 2nd, 381-553; 3rd, 554-727; 4th, 728-1074; 5th, >1,074.
↵§ Quintiles for estradiol (pmol/L): 1st, <14; 2nd, 14-17; 3rd, 18-24; 4th, 25-32; 5th, >32.