Table 1.
Age and age-standardizeda characteristics of participants in the Nurses’ Health Study (NHS) in 1994 and the Nurses’ Health Study II (NHSII) in 1995 by study population and by the highest and lowest quintile of choline intake.
| NHS | NHSII | |||
|---|---|---|---|---|
| Choline (n = 49,108) | Choline (n =74,453) | |||
| Quintile | 1 | 5 | 1 | 5 |
| Sample size | 8794 | 9838 | 14,251 | 14,966 |
| Means | ||||
| Age (years) | 59.1 | 61.5 | 39.5 | 40.9 |
| Age at menarche (years) | 12.6 | 12.3 | 12.5 | 12.3 |
| Parity (among parous women) | 3.2 | 3.1 | 2.2 | 2.2 |
| Duration of oral contraceptive use (among users, months) | 24.1 | 25.4 | 50.3 | 51.2 |
| Current body mass index (kg/m2) | 25.4 | 27.7 | 25.0 | 26.6 |
| Height (meters) | 1.6 | 1.6 | 1.7 | 1.7 |
| Caloric intake (kcal/day) | 1685 | 1693 | 1771 | 1778 |
| Caffeine intake (mg/day) | 264 | 329 | 195 | 287 |
| Alcohol consumption (g/day) | 6.0 | 5.5 | 2.7 | 3.6 |
| Percentages | ||||
| Parous | 94% | 93% | 75% | 79% |
| Oral contraceptive use | 48% | 51% | 85% | 85% |
| Premenopausalb | 13% | 12% | 95% | 95% |
| Postmenopausalb | 87% | 88% | 2% | 3% |
| Family history of ovarian cancerc | 3% | 3% | 2% | 2% |
| History of tubal ligation | 21% | 21% | 22% | 24% |
| Hysterectomy | 20% | 24% | 6% | 7% |
| Current postmenopausal hormone user (among postmenopausal women) | 35% | 39% | 65% | 61% |
a
All factors except age were age-standardized in five-year intervals for each cohort. Results for quintiles of betaine are comparable (data not shown).
b
The percentages for premenopausal and postmenopausal do not add to 100% due to women with unknown menopausal status.
c
Mother or sister had ovarian cancer according to participant’s response on questionnaire; family history was evaluated using data from 1992 for NHS because it was not available in previous cycles.