Long-term exposure to traffic-related air pollution associated with blood pressure and self-reported hypertension in a Danish cohort.
BACKGROUND
Short-term exposure to air pollution has been associated with changes in blood pressure (BP) and emergency department visits for hypertension, but little is known about the effects of long-term exposure to traffic-related air pollution on BP and hypertension.


OBJECTIVE
We studied whether long-term exposure to air pollution is associated with BP and hypertension.


METHODS
In 1993-1997, 57,053 participants 50-64 years of age were enrolled in a population-based cohort study. Systolic and diastolic BP (SBP and DBP, respectively) were measured at enrollment. Self-reported incident hypertension during a mean follow-up of 5.3 years was assessed by questionnaire. We used a validated dispersion model to estimate residential long-term nitrogen oxides (NO(x)), a marker of traffic-related air pollution, for the 1- and 5-year periods prior to enrollment and before a diagnosis of hypertension. We conducted a cross-sectional analysis of associations between air pollution and BP at enrollment with linear regression, adjusting for traffic noise, measured short-term NO(x), temperature, relative humidity, and potential lifestyle confounders (n = 44,436). We analyzed incident hypertension with Cox regression, adjusting for traffic noise and potential confounders.


RESULTS
A doubling of NO(x) exposure during 1- and 5-year periods preceding enrollment was associated with 0.53-mmHg decreases [95% confidence interval (CI): -0.88, -0.19 mmHg] and 0.50-mmHg decreases (95% CI: -0.84, -0.16 mmHg) in SBP, respectively. Long-term exposure also was associated with a lower prevalence of baseline self-reported hypertension (per doubling of 5-year mean NO(x): odds ratio = 0.96; 95% CI: 0.91, 1.00), whereas long-term NO(x) exposure was not associated with incident self-reported hypertension during follow-up.


CONCLUSIONS
Long-term exposure to traffic-related air pollution was associated with a slightly lower prevalence of BP at baseline, but was not associated with incident hypertension.
Institute of Cancer Epidemiology, Danish Cancer Society, Copenhagen, Denmark. mettes@cancer.dk
Mette
M
Sørensen
Barbara
B
Hoffmann
Martin
M
Hvidberg
Matthias
M
Ketzel
Steen Solvang
SS
Jensen
Zorana Jovanovic
ZJ
Andersen
Anne
A
Tjønneland
Kim
K
Overvad
Ole
O
Raaschou-Nielsen
D000393:Air Pollutants / Q000633:toxicity*; D001336:Automobiles; D001794:Blood Pressure; D002947:Cities / Q000453:epidemiology; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D003718:Denmark / Q000453:epidemiology; D005260:Female; D006801:Humans; D006973:Hypertension / Q000139:chemically induced / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D009589:Nitrogen Oxides / Q000633:toxicity*; D009624:Noise, Transportation / Q000009:adverse effects*; D015995:Prevalence; D011446:Prospective Studies; D012044:Regression Analysis; D012307:Risk Factors; D012621:Seasons; D013997:Time Factors; D001335:Vehicle Emissions / Q000633:toxicity*
D000393:Air Pollutants; D009589:Nitrogen Oxides; D001335:Vehicle Emissions