Lifestyle in progression from hypertensive disorders of pregnancy to chronic hypertension in Nurses' Health Study II: observational cohort study

Abstract

Objectives To study the association between lifestyle risk factors and chronic hypertension by history of hypertensive disorders of pregnancy (HDP: gestational hypertension and pre-eclampsia) and investigate the extent to which these risk factors modify the association between HDP and chronic hypertension.Design Prospective cohort study.Setting Nurses' Health Study II (1991-2013).Participants 54 588 parous women aged 32 to 59 years with data on reproductive history and without previous chronic hypertension, stroke, or myocardial infarction.Main outcome measure Chronic hypertension diagnosed by a physician and indicated through nurse participant self report. Multivariable Cox proportional hazards models were used to investigate the development of chronic hypertension contingent on history of HDP and four lifestyle risk factors: post-pregnancy body mass index, physical activity, adherence to the Dietary Approaches to Stop Hypertension (DASH) diet, and dietary sodium/potassium intake. Potential effect modification (interaction) between each lifestyle factor and previous HDP was evaluated with the relative excess risk due to interaction.Results 10% (n=5520) of women had a history of HDP at baseline. 13 971 cases of chronic hypertension occurred during 689 988 person years of follow-up. Being overweight or obese was the only lifestyle factor consistently associated with higher risk of chronic hypertension. Higher body mass index, in particular, also increased the risk of chronic hypertension associated with history of HDP (relative excess risk due to interaction P<0.01 for all age strata). For example, in women aged 40-49 years with previous HDP and obesity class I (body mass index 30.0-34.9), 25% (95% confidence interval 12% to 37%) of the risk of chronic hypertension was attributable to a potential effect of obesity that was specific to women with previous HDP. There was no clear evidence of effect modification by physical activity, DASH diet, or sodium/potassium intake on the association between HDP and chronic hypertension.Conclusion This study suggests that the risk of chronic hypertension after HDP might be markedly reduced by adherence to a beneficial lifestyle. Compared with women without a history of HDP, keeping a healthy weight seems to be especially important with such a history.

Fig 1 Cumulative incidence of chronic hypertension in parous women by lifestyle risk factors and history of hypertensive disorders of pregnancy (HDP). For body mass index (BMI), the comparison is between women with low normal weight (18.5-22.4) and women with obesity class I (30.0-34.9). For Dietary Approaches to Stop Hypertension (DASH) diet and physical activity, the comparison is first versus fourth quarter, and for sodium/potassium, the comparison is fourth versus first quarter. Survival data shown here are prepared for regression analyses, which are divided into three separate Cox proportional hazards models by age: 32-39, 40-49, and 50-59 years

Fig 2 Additive interaction of body mass index (BMI) and history of hypertensive disorders of pregnancy (HDP) on risk of chronic hypertension in women by age and BMI presented as hazard ratios partitioned into relative excess risks due to BMI, HDP, and their interaction (RERI). For each category of BMI, relative excess risk due to each risk factor (BMI or HDP) and their additive interaction (RERI) are shown; the latter is supported if RERI >0. For example, in women with BMI≥35.0, RERI is calculated as: RERI_BMI≥35.0=HR_{BMI≥35.0, HDP}−HR_{BMI 18.5 to 22.4, HDP}−HR_{BMI≥35.0, No HDP}+1. All hazard ratios are adjusted for age, race/ethnicity, parity, history of gestational diabetes mellitus, diet, physical activity, non-steroidal anti-inflammatory drug use, menopausal status, alcohol, smoking, and parental history of chronic hypertension