Table 4.
Odds ratios, expected beta coefficients, and normalized beta coefficients for ovarian cancer by individual components of lifetime ovulatory years
| Lifetime ovulatory years component | OR (95% CI)a | Expected estimate of coefficient | Normalized coefficientb | P for removal of component from model |
|---|---|---|---|---|
| Age at last menstrual period before diagnosis or interview | ||||
| Per year | 1.011 (1.004 to 1.019) | 1 (defined) | 1 | .004 |
| Age at menarche | ||||
| Per year | 1.002 (0.985 to 1.018) | −1 | 0.13 | .86 |
| Duration of oral contraceptive use, y | ||||
| Per year | 0.950 (0.945 to 0.956) | −1 | −4.45 | <.001 |
| No. of incomplete pregnancies | ||||
| Per pregnancy | 0.968 (0.944 to 0.992) | −0.25 | −2.89 | .009 |
| Number of full-term births | ||||
| Per pregnancy | 0.877 (0.857 to 0.897) | −0.75 | −11.53 | <.001 |
| Total years of breastfeeding | ||||
| Per year | 0.858 (0.816 to 0.901) | −1.0 | −13.45 | <.001 |
Adjusted for study site, age, self-reported race (Asian, Black, Other [as defined by participants as not being Asian, Black or White], Unknown, White), education (less than high school, completed high school, completed some college, completed college or university bachelor degree, completed graduate or professorial degree, unknown), body mass index 1 or 5 years prior (underweight, normal, overweight, obese, unknown), smoking status (never, former, current, unknown), family history (yes, no, unknown), and other components of lifetime ovulatory cycles in the model. CI = confidence interval; OR = odds ratio.
Normalized to the beta coefficient of age at last menstrual period.