Table 1.
Distribution of Potential Risk Factors for Endometriosis According to Total Dairy Food Intake Among Women in Nurses’ Health Study II (n = 70,556), 1991–2005a
| No. of Servings of Total Dairy Foods |
||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| ≤4/Week (n = 3,332) |
5–6/Week (n = 5,482) |
1/Day (n = 3,771) |
2/Day (n = 24,155) |
3/Day (n = 13,888) |
>3/Day (n = 19,928) |
|||||||
| % | Mean | % | Mean | % | Mean | % | Mean | % | Mean | % | Mean | |
| Age, years | 36.6 | 36.3 | 36.2 | 35.8 | 35.6 | 35.0 | ||||||
| Caucasian race | 84.1 | 88.3 | 89.5 | 92.2 | 93.7 | 94.2 | ||||||
| Body mass indexb | ||||||||||||
| 25–29.9 (overweight) | 16.7 | 17.2 | 17.5 | 18.6 | 18.8 | 18.0 | ||||||
| ≥30 (obese) | 12.1 | 12.9 | 12.8 | 12.4 | 12.3 | 11.1 | ||||||
| Cigarette smoking | ||||||||||||
| Never smoker | 64.1 | 64.6 | 66.4 | 65.8 | 67.1 | 67.1 | ||||||
| Past smoker | 19.2 | 20.0 | 19.7 | 21.9 | 22.9 | 22.5 | ||||||
| Current smoker | 16.6 | 15.3 | 13.8 | 12.2 | 9.9 | 10.3 | ||||||
| Age at menarche, years | ||||||||||||
| <12 | 24.4 | 24.6 | 23.4 | 23.7 | 23.6 | 22.9 | ||||||
| 12 | 29.5 | 31.0 | 31.5 | 30.5 | 30.3 | 30.1 | ||||||
| 13 | 26.9 | 26.1 | 27.9 | 27.9 | 28.4 | 28.2 | ||||||
| ≥14 | 18.9 | 18.1 | 16.9 | 17.7 | 17.4 | 18.7 | ||||||
| Menstrual cycle length, days | ||||||||||||
| <26 | 14.5 | 13.5 | 12.5 | 11.8 | 10.8 | 9.8 | ||||||
| 26–31 | 64.8 | 66.0 | 66.9 | 66.7 | 67.4 | 67.6 | ||||||
| 32–50 | 15.8 | 16.4 | 17.0 | 17.1 | 17.3 | 17.9 | ||||||
| Ever use of oral contraceptives | 81.7 | 83.6 | 84.7 | 84.1 | 83.5 | 82.4 | ||||||
| Nulliparous | 32.4 | 31.8 | 29.9 | 28.1 | 26.2 | 21.9 | ||||||
| Duration of lactation (among parous women), months | ||||||||||||
| None | 14.1 | 13.5 | 12.8 | 11.1 | 9.6 | 8.5 | ||||||
| ≥12 | 18.6 | 20.0 | 21.7 | 25.3 | 30.3 | 37.3 | ||||||
| No recent gynecological examination | 18.5 | 16.5 | 16.1 | 14.5 | 13.4 | 13.3 | ||||||
a All data shown are standardized to the age distribution of the 1991 cohort.
b Weight (kg)/height (m)2.