Table 1.
Characteristics of study population by the frequency of any analgesic use at urine collection in the Nurses' Health Study II (n = 603)
| Frequency of any analgesic use (days/week) | ||||
|---|---|---|---|---|
| 0 | 1 | 2–3 | 4+ | |
| 194 | 150 | 134 | 125 | |
| Age in years | 42.6 (4.0) | 42.6 (3.7) | 43.1 (3.7) | 43.4 (3.8) |
| Body mass index (kg/m2) | 23.9 (3.7) | 24.7 (4.0) | 25.3 (4.1) | 26.9 (4.9) |
| Height (inches) | 64.9 (2.4) | 65.4 (2.0) | 64.8 (2.3) | 65.2 (2.0) |
| Physical activity (MET-h/week)a | 23.1 (19.2) | 20.7 (15.7) | 22.4 (15.4) | 22.4 (17.7) |
| Parous, % | 85.8 | 77.8 | 85.4 | 76.0 |
| Parityb | 2.1 (1.0) | 1.7 (1.0) | 2.0 (1.0) | 1.8 (1.0) |
| Age at first birthb (years) | 26.5 (3.6) | 26.3 (4.1) | 26.7 (4.2) | 26.2 (3.7) |
| Past oral contraceptive use, % | 77.9 | 87.0 | 89.2 | 87.4 |
| Alcohol intake (g/day)c | 3.7 (5.2) | 4.3 (5.0) | 4.7 (6.6) | 3.6 (4.4) |
| Current smoker, % | 5.9 | 6.4 | 7.4 | 8.9 |
| Age at menarche <12 years, % | 19.2 | 19.9 | 21.2 | 25.7 |
| Menstrual cycle length 26–31 days, % | 72.5 | 60.0 | 67.4 | 74.1 |
| Regular menstrual cyclesd | 97.1 | 92.7 | 96.5 | 93.8 |
| First morning urine, % | 88.3 | 75.3 | 80.2 | 78.5 |
| Luteal day outside 3–10 days before next period, % | 12.7 | 11.8 | 15.9 | 14.1 |
| Anovulatory cycle, % | 9.4 | 5.7 | 7.7 | 14.9 |
| Creatinine, mg/L | 1,150 (542) | 1,132 (439) | 1,170 (503) | 1,034 (446) |
Values are means (SD) or percentages and are standardized to the age distribution of the study population
aAverage of 1997 and 2001 activities
bAmong parous women
cAverage of 1995 and 1999 intakes
dMenstrual cycles begin within 5–7 days of expected