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Is there a differential impact of parity on blood pressure by age?

Dratva, Juliaa,b; Schneider, Corneliaa,b; Schindler, Christiana,b; Stolz, Daianac; Gerbase, Margaretd; Pons, Marcoe; Bettschart, Robertf; Gaspoz, Jean-Michelg; Künzli, Ninoa,b; Zemp, Elisabetha,b; Probst-Hensch, Nicolea,b

doi: 10.1097/HJH.0000000000000325

Objective: In pregnancy, women experience metabolic and hemodynamic changes of potential long-term impact. Conflicting evidence exists on the impact on blood pressure (BP). We investigated the association between parity and BP in the Swiss Study on Air Pollution And Lung and Heart Disease In Adults cohort.

Methods: Multilevel linear and logistic regression analyses were performed in 2837 women aged 30–73 years, with data on parity, number of births, BP, and doctor-diagnosed hypertension adjusting for potential confounders. Hypertension was defined as at least 140/90 mmHg, doctor diagnosed or taking relevant treatment. Stratified analyses were performed by age (<40, 40–59, and ≥60 years) and menopausal status.

Results: Parous women had a mean of 2.3 pregnancies (SD 0.95, range 1–7). A total of 26% were nulliparous. Mean BP was 119/76 mmHg in nulliparous and 121/76 mmHg in parous women. Parity had a significant adverse effect on BP in women at least 60 years [SBP 5.6 mmHg, 95% confidence interval (CI) 2.3 to 8.9; DBP 1.8 mmHg, 95% CI 0.1 to 3.6] and protective effect in women below 40 years (SBP −3.4 mmHg, 95% CI –5.8 to −1.0; DBP −0.2 mmHg, 95% CI −1.0 to 0.6). With increasing number of births, SBP (mmHg/birth; 95% CI) increased in older (1.2, 95% CI 0.2 to 2.2) and decreased in younger women (−1.6, 95% CI −2.6 to −0.5). Opposite effects of parity were also found for diagnosed hypertension. No interaction by menopausal status was found.

Conclusion: Our analyses yield differential effects of parity on BP in older vs. younger women. Reductions in BP in younger parous women have been described before; the opposite impact in older women is new. The findings may constitute biological mechanisms in an aging population or reflect birth cohort effects.

aDepartment of Epidemiology and Public Health, Swiss Tropical and Public Health Institute

bUniversity of Basel,

cKlinik für Pneumologie, Universitätsspital Basel, Basel

dDivision of Pulmonary Medicine, University Hospitals, Geneva

eLungenpraxis Hirslanden Klinik Aarau, Aarau

fOspedale Regionale di Lugano, Lugano

gDepartment of Community Medicine and Primary Care, University Hospitals, Geneva, Switzerland

Correspondence to Julia Dratva, Swiss TPH, Socinstrasse 57, P.O. Box, 4002 Basel, Switzerland. Tel: +41 61 284 81 11; fax: +41 61 284 81 01; e-mail:

Abbreviations: BP, blood pressure; CVD, cardiovascular disease; SAPALDIA, Swiss Study on Air Pollution and Lung and Heart Disease in Adults

Received 19 February, 2014

Revised 30 June, 2014

Accepted 1 July, 2014

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