Table 1.
Baseline Characteristics of Women in the Study Sample (n = 106,256), by Smoking Statusa, Nurses’ Health Study II, 1989–2011b
| Characteristic | Smoking Status at Baseline | P Valuec | |||||
|---|---|---|---|---|---|---|---|
| Never (n = 69,881; 65.8%) |
Past (n = 22,619; 21.3%) |
Current (n = 13,756; 12.9%) |
|||||
| Mean (SE) | % | Mean (SE) | % | Mean (SE) | % | ||
| Age, years | 33.7 (0.02) | 35.0 (0.03) | 34.4 (0.04) | <0.0001 | |||
| BMId | 24.0 (0.02) | 24.0 (0.03) | 24.0 (0.04) | 0.9 | |||
| Physical activity, MET-hours/week | 28.4 (0.26) | 29.6 (0.46) | 26.6 (0.59) | <0.0001 | |||
| Alcohol consumption, g/day | 2.2 (0.02) | 4.0 (0.04) | 5.0 (0.05) | <0.0001 | |||
| Duration of OC use, months | 40.2 (0.17) | 50.2 (0.30) | 53.8 (0.38) | <0.0001 | |||
| Age at menarche, years | 12.4 (0.01) | 12.4 (0.01) | 12.4 (0.01) | <0.01 | |||
| Parity | 1.4 (0.01) | 1.4 (0.01) | 1.3 (0.01) | <0.0001 | |||
| Breastfeeding duration, months | 13.9 (0.06) | 12.8 (0.11) | 8.8 (0.15) | <0.0001 | |||
| Vegetable protein (% of diet) | 5.0 (0.01) | 5.1 (0.01) | 4.7 (0.01) | <0.0001 | |||
| Vitamin D (IU/day) | |||||||
| Total (energy adjusted) | 393 (1.1) | 400 (1.9) | 354 (2.5) | <0.0001 | |||
| Dietary (energy adjusted) | 255 (0.5) | 259 (0.9) | 230 (1.2) | <0.0001 | |||
| Dairy (energy adjusted) | 133 (0.4) | 129 (0.8) | 118 (1.0) | <0.0001 | |||
| Supplemental | 137 (0.9) | 141 (1.6) | 124 (2.1) | <0.0001 | |||
| Calcium, mg/day | |||||||
| Total (energy adjusted) | 1,025 (1.8) | 1,036 (3.1) | 940 (4.1) | <0.0001 | |||
| Dietary (energy adjusted) | 892 (1.3) | 903 (2.2) | 831 (2.9) | <0.0001 | |||
| Dairy (energy adjusted) | 584 (1.3) | 583 (2.3) | 528 (2.9) | <0.0001 | |||
| Supplemental | 133 (1.3) | 133 (2.2) | 108 (2.9) | <0.0001 | |||
| Racee | <0.0001 | ||||||
| Non-Hispanic white | 92.9 | 96.4 | 95.4 | ||||
| Asian | 2.6 | 0.7 | 0.8 | ||||
| Other | 4.5 | 2.9 | 3.7 | ||||
Abbreviations: BMI, body mass index; IU, international unit; MET, metabolic equivalent of task; OC, oral contraceptive; SE, standard error.
a All comparisons other than age at baseline were adjusted for age.
b The study sample included women in the Nurses’ Health Study II who were premenopausal, at risk of early natural menopause, and free of cancer and for whom data on smoking status at baseline were available.
c P values from χ2 test or general linear models as appropriate.
d Weight (kg)/height (m)2.
e Age-adjusted estimates from general linear models of percent of each race category.