Short-term impact of ambient air pollution and air temperature on blood pressure among pregnant women.

BACKGROUND

Epidemiologic studies have reported inconsistent findings for the association between air pollution levels and blood pressure (BP), which has been studied mainly in elderly subjects. Short-term air pollution effects on BP have not been investigated in pregnant women, who may constitute a vulnerable population.

METHODS

Between 2002 and 2006, 1500 pregnant women from a mother-child cohort study conducted in Nancy and Poitiers, France, underwent 11,220 repeated BP measurements (average, 7.5 measurements/woman). Nitrogen dioxide (NO₂), particulate matter with an aerodynamic diameter below 10 μm (PM₁₀), and meteorologic variables were measured on an hourly basis at permanent monitoring sites. We studied changes of BP in relation to short-term variations of air pollution and temperature with mixed models adjusted for meteorologic and personal characteristics.

RESULTS

A 10°C decrease in temperature led to an increase in systolic BP of 0.5% (95% confidence interval = 0.1% to 1.0%). Elevated NO₂-levels 1 day, 5 days and averaged over 7 days before the BP measurement were associated with reduced systolic BP. The strongest decrease was observed for the 7-day NO₂ average (-0.4% [-0.7% to -0.2%] change for an 11 μg/m³ increase in NO₂). PM₁₀ effects on systolic BP differed according to pregnancy trimester: PM₁₀ concentration was associated with systolic BP increases during the first trimester and systolic BP decreases later in pregnancy.

CONCLUSIONS

We observed short-term associations of air pollution and of temperature with BP in pregnant women. Whether such changes in BP have clinical implications remains to be investigated.