Table I.
Age-adjusted characteristics of early menopause cases and controls at the time of blood collection, Nurses’ Health Study 2, 1996–1999.
| Characteristic | Cases (n = 327) | Matched Controls (n = 327) | All Controls (n = 491) | ||
|---|---|---|---|---|---|
| mean (SE) | mean (SE) | P | mean (SE) | P | |
| Age at blood collection (yrs)a | 40.2 (2.8) | 40.2 (2.8) | 0.94 | 40.3 (2.7) | 0.54 |
| Body mass index (kg/m2) | 25.3 (0.3) | 25.0 (0.3) | 0.45 | 25.0 (0.2) | 0.38 |
| Age at menarche (yrs) | 12.4 (0.08) | 12.3 (0.07) | 0.58 | 12.4 (0.06) | 0.97 |
| Years until cycle became regular (yrs)b | 1.4 (0.08) | 1.7 (0.09) | 0.01 | 1.6 (0.07) | 0.05 |
| Pack years of cigarette smokingc | 13.0 (0.8) | 10.7 (0.8) | 0.07 | 10.7 (0.7) | 0.03 |
| Parity (number of pregnancies ≥6 mo)d | 2.3 (0.06) | 2.4 (0.06) | 0.33 | 2.4 (0.05) | 0.31 |
| Duration of exclusive breast feeding (mo)d | 5.1 (0.4) | 6.9 (0.4) | 0.002 | 6.7 (0.3) | 0.002 |
| Duration of oral contraceptive use (mo) | 49.8 (3.1) | 51.3 (3.0) | 0.72 | 52.5 (2.5) | 0.50 |
| n (%) | n (%) | P | n (%) | P | |
| White racee | 312 (95.4) | 323 (98.8) | 0.01 | 479 (97.5) | 0.09 |
| Non-Hispanic ethnicitye | 317 (96.9) | 325 (99.4) | 0.04 | 487 (99.2) | 0.02 |
| Current smoker | 46 (14.0) | 30 (9.2) | 0.05 | 47 (9.6) | 0.05 |
| Former smoker | 59 (18.0) | 80 (24.5) | 0.04 | 122 (24.9) | 0.02 |
| Nulliparous | 76 (23.2) | 64 (19.6) | 0.37 | 102 (20.8) | 0.37 |
| Physical activity >1 time/week | 133 (40.7) | 137 (41.9) | 0.75 | 217 (44.2) | 0.32 |
| Alcohol intake ≥1 drink/day | 18 (5.5) | 29 (8.9) | 0.10 | 45 (9.2) | 0.06 |
| History of infertility | 87 (26.6) | 59 (18.0) | 0.009 | 120 (24.4) | 0.48 |
| Current exogenous hormone use | 13 (4.0) | 3 (0.9) | 0.01 | 11 (2.2) | 0.12 |
aMatching factor; standard deviation shown for age rather than standard error.
bAmong women whose cycles ever became regular (n = 757).
cLimited to ever smokers.
dLimited to parous women.
eParticipants are asked to best describe their race, with response options of White; Black or African American; Asian; American Indian/Alaskan Native; Native Hawaiian or Pacific Islander; Other. Respondents can select multiple options. Participants are also asked if they consider themselves to be Spanish/Hispanic/Latina (yes/no).