Table 1. Selected baseline characteristics by category of first-degree relative network size, in the WHI (N = 4,530).
| Size of relative networks | |||||
|---|---|---|---|---|---|
|
|
|||||
| 0–3 | 4–5 | 6–9 | 10 or more | P-trend | |
| N | 1,218 | 1,513 | 1,412 | 387 | |
| Person-years | 8,519 | 10,450 | 9,632 | 2,583 | |
| Family history of breast cancer (%) | 16.1 | 17.2 | 21.8 | 24.5 | <0.001 |
| Medical visit within last year (%) | 83.2 | 82.4 | 82.7 | 81.6 | 0.54 |
| Mammogram within last 2 years (%) | 11.6 | 12.5 | 14.1 | 16.6 | 0.005 |
| Demographic variables | |||||
| Age (mean years) | 63.8 | 63.7 | 63.7 | 63.9 | 0.85 |
| Ethnicity (%) | |||||
| Caucasian | 90.5 | 91.9 | 85.9 | 70.2 | <0.001** |
| African–American | 6.3 | 6.1 | 4.3 | 16.6 | |
| Asian | 1.1 | 1.3 | 3.8 | 4.4 | |
| Hispanic/Latino | 1.2 | 1.7 | 2.8 | 6.5 | |
| Other | 0.7 | 0.8 | 1.1 | 1.0 | |
| Education ≥ college (%) | 81.1 | 73.7 | 66.5 | 51.3 | <0.001 |
| Income ($, mean) | 55,983 | 56,051 | 50,806 | 41,629 | <0.001 |
| Severity of disease | |||||
| Stage | |||||
| Localized (%) | 73.3 | 72.5 | 73.8 | 69.4 | 0.41** |
| Regional (%) | 22.8 | 24.9 | 22.9 | 27.0 | |
| Distant (%) | 1.1 | 0.9 | 1.1 | 1.5 | |
| No nodal involvement (%) | 72.8 | 72.5 | 74.0 | 69.4 | 0.35 |
| Tumor >3 mm (%) | 94.6 | 92.2 | 93.8 | 92.5 | 0.45 |
| ER positive tumor (%) | 77.9 | 76.7 | 74.7 | 71.5 | 0.004 |
| HER-2-neu receptor + (%) | 19.5 | 18.7 | 19.1 | 24.0 | 0.24 |
| Behavioral factors | |||||
| Body mass index (kg/m2) | 27.6 | 28.0 | 28.5 | 29.9 | <0.001 |
| Physical activity (METS/wk) | 12.3 | 12.2 | 11.9 | 11.1 | 0.08 |
| Never smokers (%) | 86.1 | 89.1 | 88.1 | 88.6 | 0.37 |
| Fat intake >30% (%) | 61.4 | 62.8 | 64.8 | 72.9 | <0.001 |
| Alcohol intake (servings/wk) | 3.4 | 2.8 | 2.3 | 1.4 | <0.001 |
| Reproductive factors | |||||
| Age at menopause (mean years) | 48.9 | 48.9 | 48.6 | 48.6 | 0.12 |
| Ever live birth (%) | 65.0 | 92.0 | 95.8 | 97.2 | <0.001 |
| Age at menarche <12 years (%) | 25.6 | 24.6 | 21.5 | 23.0 | 0.02 |
| Age at first birth >30 years (%) | 21.0 | 11.4 | 7.2 | 8.2 | <0.001 |
| Ever breast feeding (%) | 34.6 | 52.1 | 58.5 | 61.3 | <0.001 |
| Social variables | |||||
| Social support score (mean) | 35.4 | 36.5 | 36.5 | 35.4 | 0.23 |
| Social strain score (mean) | 1.6 | 1.6 | 1.6 | 1.8 | <0.001 |
| Provide caregiving (%) | 37.0 | 37.9 | 42.3 | 39.3 | 0.03 |
| Number of children (mean) | 1.1 | 2.4 | 3.3 | 4.3 | <0.001 |
| First-degree relatives (mean) | 2.2 | 4.5 | 7.0 | 11.7 | <0.001 |
| Married (%) | 53.8 | 66.6 | 66.4 | 66.3 | <0.001 |
| Religious participation (%) | 35.0 | 40.5 | 47.8 | 57.8 | <0.001 |
| Club participation (%) | 59.4 | 58.7 | 55.8 | 52.0 | <0.001 |
Except for age, all variables age-adjusted
**
P value, Mantel–Haenszel χ2 test, not for trend, age-adjusted