Table 2. Age-standardiseda characteristics in 1988 (Nurses' Health Study) and 1989 (Nurses' Health Study II) by body size measures and study population.
|
Average childhood body fatnessb
|
BMI at the age of 18 years, kg m−2
|
Height, m
|
Birthweight, lbs
|
|||||
|---|---|---|---|---|---|---|---|---|
| 1 | ⩾5 | <20 | ⩾25 | <1.6 | ⩾1.75 | <5.5 | ⩾8.5 | |
| Nurses' Health Study (NHS) | ||||||||
| Sample size at baselinec | 19 371 | 4633 | 29 077 | 8212 | 24 877 | 5165 | 3312 | 6868 |
| Means | ||||||||
| Age (years) | 55.4 | 53.9 | 54.4 | 54.6 | 55.0 | 53.8 | 53.6 | 54.9 |
| Age at menarche (years) | 12.8 | 12.2 | 12.8 | 12.2 | 12.3 | 12.9 | 12.4 | 12.6 |
| Parity (among parous women) | 3.2 | 3.0 | 3.1 | 3.1 | 3.2 | 3.0 | 3.1 | 3.1 |
| Duration of oral contraceptive use (months) | 24.6 | 24.0 | 25.2 | 23.2 | 22.9 | 23.2 | 25.9 | 24.7 |
| Current body mass index (kg m−2) | 24.4 | 28.1 | 23.4 | 30.8 | 25.7 | 25.1 | 25.5 | 26.1 |
| Percentages | ||||||||
| Parous | 93.0 | 92.3 | 92.5 | 90.8 | 92.4 | 90.5 | 92.6 | 92.5 |
| Premenopausal | 31.6 | 31.7 | 27.8 | 27.1 | 25.2 | 25.5 | 34.2 | 33.3 |
| Postmenopausal | 68.2 | 68.2 | 70.1 | 70.6 | 69.3 | 69.7 | 65.0 | 65.8 |
| Family history of ovarian cancerd | 2.6 | 2.8 | 2.5 | 2.9 | 2.2 | 2.7 | 3.0 | 2.6 |
| History of tubal ligation | 17.4 | 17.9 | 17.0 | 18.3 | 17.0 | 15.5 | 19.3 | 18.2 |
| Current postmenopausal hormone user (among postmenopausal women) | 25.3 | 22.3 | 27.8 | 20.9 | 25.2 | 26.8 | 23.4 | 24.8 |
|
Nurses' Health Study II (NHSII)
| ||||||||
| Sample size at baselinec | 19 220 | 6984 | 44 078 | 11 745 | 21 440 | 8922 | 2834 | 11 467 |
| Means | ||||||||
| Age (years) | 34.6 | 34.8 | 34.3 | 34.3 | 34.5 | 34.0 | 35.0 | 33.7 |
| Age at menarche (years) | 12.8 | 12.0 | 12.7 | 12.0 | 12.2 | 12.7 | 12.3 | 12.5 |
| Parity (among parous women) | 2.1 | 2.0 | 2.1 | 2.0 | 2.0 | 2.0 | 2.1 | 2.1 |
| Duration of oral contraceptive use (months) | 46.9 | 43.0 | 45.6 | 39.3 | 42.7 | 44.1 | 45.7 | 43.3 |
| Current body mass index (kg m−2) | 22.1 | 27.6 | 21.4 | 31.3 | 24.3 | 23.9 | 24.1 | 24.5 |
| Percentages | ||||||||
| Parous | 69.9 | 62.5 | 70.8 | 56.7 | 70.2 | 64.8 | 68.0 | 67.3 |
| Premenopausal | 99.0 | 98.6 | 99.0 | 98.3 | 98.7 | 99.1 | 98.7 | 98.8 |
| Family history of ovarian cancerd | 1.5 | 1.9 | 1.5 | 1.8 | 1.5 | 1.6 | 1.8 | 1.5 |
| History of tubal ligation | 16.5 | 16.1 | 15.1 | 14.9 | 17.3 | 13.6 | 17.1 | 14.5 |
a
All factors except age were age-standardised in 5-year intervals for each cohort.
b
Average childhood body fatness was calculated by taking the average of each participant's body fatness at ages 5 and 10 years, using a nine-level figure drawing.
c
Baseline for each analysis was the year when the body size measure was assessed (see Table 1).
d
Mother or sister had ovarian cancer according to the participant's response on the questionnaire; family history was evaluated using data from 1992 for NHS and 1993 for NHSII because it was not available in previous cycles.