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. 2011 Oct 12;174(10):1147–1158. doi: 10.1093/aje/kwr227

Table 2.

Association Between Duration of Breastfeeding for the First Child and Incident Hypertension Among 55,636 Parous Women in the Nurses’ Health Study II, United States, 1991–2005a

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.

a

Inverse probability weight-adjusted Cox proportional hazards regression models were used.

b

Adjusted for participant’s age and follow-up time in months.

c

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.

d

BMI during follow-up modeled by using a 3-knot quadratic spline.