Table 1.
Selected characteristics of the population (N = 573)
| Characteristics | Missing values (N) | Mean (SD) or N (%) |
|---|---|---|
| State of recruitment | 0 | |
| Jalisco | 318 (55.5) | |
| Veracruz | 255 (44.5) | |
| Breast density (%) | 0 | 36.5 (17.0) |
| Dense tissue area (cm2) | 0 | 48.4 (33.3) |
| Non-dense area (cm2) | 0 | 82.3 (38.5) |
| Age at mammography (years) | 0 | 43.1 (3.7) |
| Age at menarche (years) | 4 | 12.6 (1.5) |
| Family history of breast cancer (yes) | 0 | 27 (4.7) |
| History of benign breast disease (yes) | 0 | 79 (13.8) |
| Oral contraceptive use (ever) | 19 | 288 (52.0) |
| Number of full-term pregnancies | 30 | 2.1 (1.2) |
| Age at first birtha (years) | 43 | 24.8 (4.4) |
| Duration of breastfeedinga | 41 | |
| No breastfeeding | 49 (10.4) | |
| < 6 months | 96 (20.4) | |
| 6 to 12 months | 100 (21.3) | |
| 12 to 24 months | 133 (28.3) | |
| ≥ 24 months | 92 (19.6) | |
| Physical activity (MET hours/week) | 1 | 26.5 (21.1) |
| Alcohol intake (drinks/day) | 45 | |
| 0 | 160 (30.3) | |
| < 0.1 | 259 (49.1) | |
| 0.1-0.2 | 76 (14.4) | |
| ≥ 0.2 | 33 (6.3) | |
| Smoking status | 62 | |
| Never | 366 (71.6) | |
| Past | 87 (17.0) | |
| Current | 58 (11.4) | |
| BMI (kg/m2) | 0 | 28.4 (5.4) |
| < 25 | 168 (29.3) | |
| 25-30 | 214 (37.4) | |
| ≥30 | 191 (33.3) | |
| Socioeconomic status | 79 | |
| Low | 84 (17.0) | |
| Medium | 216 (43.7) | |
| High | 194 (39.3) |
aAmong parous women (n = 511)
Abbreviations: BMI body mass index; SD standard deviation