Table 2.
Duration | No. of Cases | Person-Years | Age-adjusted Hazard Ratiob | 95% CI | Age- and IPW-adjusted Hazard Ratioc | 95% CI | Age-, IPW-,c and Current BMI-adjusted Hazard Ratiod | 95% CI |
Total breastfeeding | ||||||||
Never | 2,179 | 126,012 | 1.46 | 1.36, 1.57 | 1.27 | 1.18, 1.36 | 1.22 | 1.13, 1.31 |
>0–3 months | 1,459 | 95,475 | 1.46 | 1.35, 1.57 | 1.29 | 1.20, 1.39 | 1.24 | 1.15, 1.33 |
>3–<6 months | 1,639 | 125,370 | 1.28 | 1.19, 1.38 | 1.16 | 1.08, 1.25 | 1.13 | 1.05, 1.22 |
6–<9 months | 1,356 | 111,970 | 1.17 | 1.08, 1.26 | 1.11 | 1.03, 1.19 | 1.09 | 1.01, 1.17 |
9–<12 months | 1,014 | 89,853 | 1.07 | 0.99, 1.17 | 1.03 | 0.95, 1.11 | 1.03 | 0.96, 1.11 |
≥12 months | 1,214 | 112,200 | 1.00 | Referent | 1.00 | Referent | 1.00 | Referent |
Ptrend | <0.001 | <0.001 | <0.001 | |||||
Exclusive breastfeeding | ||||||||
Never breastfed | 2,179 | 126,012 | 1.45 | 1.34, 1.56 | 1.29 | 1.20, 1.39 | 1.22 | 1.13, 1.31 |
Breastfed, never exclusively | 2,801 | 198,791 | 1.32 | 1.23, 1.42 | 1.11 | 1.03, 1.19 | 1.07 | 1.00, 1.15 |
>0–3 months exclusively | 1,491 | 118,373 | 1.19 | 1.10, 1.29 | 1.08 | 0.99, 1.18 | 1.08 | 0.99, 1.18 |
>3–<6 months exclusively | 1,319 | 118,717 | 1.08 | 1.00, 1.17 | 1.03 | 0.95, 1.12 | 1.04 | 0.96, 1.13 |
≥6 months exclusively | 1,054 | 97,390 | 1.00 | Referent | 1.00 | Referent | 1.00 | Referent |
Ptrend | <0.001 | <0.001 | <0.001 |
Abbreviations: BMI, body mass index; CI, confidence interval; DASH, Dietary Approaches to Stop Hypertension; IPW, inverse probability weight.
Inverse probability weight-adjusted Cox proportional hazards regression models were used.
Adjusted for participant’s age and follow-up time in months.
Inverse probability weights derived from multinomial logistic regression model for probability of each breastfeeding duration category as a function of maternal BMI at age 18 years (linear and quadratic), year of first birth (linear and quadratic), self-reported history of preeclampsia, gestational hypertension, gestational diabetes, birth of an infant at <37 weeks’ gestation, birth of an infant weighing <2,500 g, miscarriage or stillbirth at >12 weeks’ gestation, smoking status, vigorous physical activity, alcohol consumption, DASH diet score quintile, family history of hypertension, current oral contraceptive use, current nonnarcotic analgesic use, and self-reported race.
BMI during follow-up modeled by using a 3-knot quadratic spline.