Table 1.
Characteristics of the Study Population Across Categories of Oral Contraceptive Use Duration, National Institutes of Health-AARP Diet and Health Study, United States, 1995–2011a
| Characteristic | Duration of Oral Contraceptive Use, years | |||||||
|---|---|---|---|---|---|---|---|---|
| No Use or <1 (n = 118,144) | 1–4 (n = 34,866) | 5–9 (n = 24,564) | ≥10 (n = 18,962) | |||||
| No. | % | No. | % | No. | % | No. | % | |
| Age at baseline, yearsb | 64 (60–67) | 59 (55–64) | 59 (55–64) | 60 (56–64) | ||||
| Race | ||||||||
| White | 105,285 | 90.4 | 31,156 | 90.6 | 22,121 | 91.2 | 17,152 | 91.5 |
| Black | 6,608 | 5.7 | 2,067 | 6.0 | 1,438 | 5.9 | 1,117 | 6.0 |
| Other | 4,530 | 3.9 | 1,184 | 3.4 | 689 | 2.8 | 469 | 2.5 |
| Educational level | ||||||||
| Did not complete high school | 8,972 | 7.9 | 1,593 | 4.7 | 959 | 4.0 | 669 | 3.6 |
| High school | 33,332 | 29.2 | 7,525 | 22.2 | 5,232 | 21.9 | 3,912 | 21.2 |
| Some college/post–high school | 40,286 | 35.3 | 12,842 | 37.9 | 9,273 | 38.8 | 7,218 | 39.0 |
| College | 15,919 | 14.0 | 5,816 | 17.2 | 4,070 | 17.0 | 3,120 | 16.9 |
| Postgraduate | 15,584 | 13.7 | 6,071 | 17.9 | 4,343 | 18.2 | 3,577 | 19.3 |
| Smoking status | ||||||||
| Nonsmoker | 54,778 | 47.8 | 14,605 | 43.2 | 9,914 | 41.5 | 7,794 | 42.3 |
| Former smoker | 43,728 | 38.2 | 13,814 | 40.8 | 10,201 | 42.7 | 7,927 | 43.0 |
| Current smoker | 16,065 | 14.0 | 5,424 | 16.0 | 3,753 | 15.7 | 2,722 | 14.8 |
| No. of cigarettes smoked per dayc | ||||||||
| Never smoked | 54,778 | 47.8 | 14,605 | 43.2 | 9,914 | 41.5 | 7,794 | 42.3 |
| 1–10 | 21,780 | 19.0 | 6,978 | 20.6 | 4,930 | 20.7 | 3,622 | 19.6 |
| 11–20 | 20,534 | 17.9 | 6,548 | 19.3 | 4,647 | 19.5 | 3,443 | 18.7 |
| 21–30 | 9,705 | 8.5 | 3,198 | 9.4 | 2,374 | 9.9 | 1,865 | 10.1 |
| 31–40 | 4,963 | 4.3 | 1,610 | 4.8 | 1,258 | 5.3 | 993 | 5.4 |
| 41–60 | 2,272 | 2.0 | 758 | 2.2 | 630 | 2.6 | 579 | 3.1 |
| ≥61 | 539 | 0.5 | 146 | 0.4 | 115 | 0.5 | 147 | 0.8 |
| Current alcohol use | ||||||||
| Nondrinker | 38,421 | 32.7 | 9,167 | 26.4 | 5,799 | 23.7 | 4,080 | 21.6 |
| ≤2 servings per day | 74,038 | 63.0 | 23,797 | 68.5 | 17,259 | 70.5 | 13,558 | 71.7 |
| >2 servings per day | 5,100 | 4.3 | 1,789 | 5.1 | 1,429 | 5.8 | 1,279 | 6.8 |
| Current body mass indexd | ||||||||
| <25 | 48,467 | 42.5 | 15,214 | 44.9 | 11,301 | 47.2 | 9,147 | 49.3 |
| 25–29 | 37,654 | 33.0 | 10,788 | 31.8 | 7,609 | 31.8 | 5,830 | 31.4 |
| ≥30 | 27,867 | 24.4 | 7,915 | 23.3 | 5,018 | 21.0 | 3,562 | 19.2 |
| Current physical activity | ||||||||
| ≥3 times per week | 48,368 | 41.5 | 14,245 | 41.2 | 10,105 | 41.5 | 8,093 | 43.0 |
| 1–2 times per week | 24,067 | 20.6 | 7,587 | 22.0 | 5,417 | 22.3 | 4,115 | 21.9 |
| ≤3 times per month | 44,149 | 37.9 | 12,709 | 36.8 | 8,823 | 36.2 | 6,598 | 35.1 |
| Age at menarche, years | ||||||||
| ≤12 | 57,460 | 48.8 | 17,343 | 49.9 | 12,002 | 49.0 | 9,259 | 48.9 |
| 13–14 | 49,035 | 41.6 | 14,297 | 41.1 | 10,341 | 42.2 | 7,791 | 41.2 |
| ≥15 years | 11,273 | 9.6 | 3,135 | 9.0 | 2,166 | 8.8 | 1,873 | 9.9 |
| Menopausal status | ||||||||
| Premenopausal | 2,224 | 1.9 | 2,256 | 6.5 | 1,606 | 6.6 | 1,130 | 6.0 |
| Postmenopausal | 115,568 | 98.1 | 32,492 | 93.5 | 22,881 | 93.4 | 17,758 | 94.0 |
| Has first degree relative with breast cancer | ||||||||
| No | 98,138 | 87.0 | 29,082 | 87.2 | 20,499 | 87.1 | 15,930 | 87.6 |
| Yes | 14,606 | 13.0 | 4,258 | 12.8 | 3,025 | 12.9 | 2,265 | 12.5 |
| Has first degree relative with colon cancer | ||||||||
| No | 101,351 | 89.9 | 30,072 | 90.2 | 21,312 | 90.6 | 16,482 | 90.6 |
| Yes | 11,393 | 10.1 | 3,268 | 9.8 | 2,212 | 9.4 | 1,713 | 9.4 |
| Has a history of diabetes | ||||||||
| No | 108,219 | 91.6 | 32,605 | 93.5 | 23,118 | 94.1 | 18,035 | 95.1 |
| Yes | 9,925 | 8.4 | 2,261 | 6.5 | 1,446 | 5.9 | 927 | 4.9 |
a Characteristics reflect the analytic population before exclusions for specific cancer analyses (e.g., women with bilateral oophorectomy were excluded from Cox models for ovarian cancer). Percentages in the table refer to proportions of the population who were not missing information on a given covariate. Missingness was less than 5% for all covariates and is not tabulated.
b Values expressed as median (interquartile range). The overall age range for the analytic population at baseline was 50–72 years.
c Number of cigarettes smoked per day was treated as a continuous variable in our models.
d Weight (kg)/height (m)2.