Residential traffic exposure, pulse pressure, and C-reactive protein: consistency and contrast among exposure characterization methods.

BACKGROUND

Traffic exposure may increase cardiovascular disease (CVD) risk via systemic inflammation and elevated blood pressure, two important clinical markers for managing disease progression.

OBJECTIVES

We assessed degree and consistency of association between traffic exposure indicators as predictors of C-reactive protein (CRP) and pulse pressure (PP) in an adult U.S. Puerto Rican population (n = 1,017).

METHODS

Cross-sectional information on health and demographics and blood data was collected. Using multiple linear regression, we tested for associations between CRP, PP, and six traffic exposure indicators including residential proximity to roads with > 20,000 vehicles/day and traffic density [vehicle miles traveled per square mile (VMT/mi2)]. Diabetes and obesity [body mass index (BMI) >or= 30 kg/m2] were tested as effect modifiers.

RESULTS

CRP was positively associated with traffic density in the total population [36% CRP difference with 95% confidence interval (CI) 2.5-81%] for residence within the highest versus lowest VMT/mi2 level. With BMI >or= 30, CRP showed significant positive associations with five of six traffic indices including residence <or= 200 m versus > 200 m of a roadway [22.7% CRP difference (95% CI, 3.15-46.1)] and traffic density in the third highest versus lowest VMT/mi2 level [28.1% difference (95% CI, 1.0-62.6)]. PP was positively associated with residence within <or= 100 m of a roadway for the total population [2.2 mmHg (95% CI, 0.13-4.3 mmHg)] and persons with BMI >or= 30 [3.8 mmHg (95% CI, 0.88-6.8)]. Effect estimates approximately doubled for residence within <or= 200 m of two or more roadways, particularly in persons with diabetes [8.1 mmHg (95% CI, 2.2-14.1)].

CONCLUSIONS

Traffic exposure at roadway volumes as low as 20,000-40,000 vehicles/day may increase CVD risk through adverse effects on blood pressure and inflammation. Individuals with elevated inflammation profiles, that is, BMI >or= 30, may be more susceptible to the effects of traffic exposure.