Gaseous air pollution and emergency hospital visits for hypertension in Beijing, China: a time-stratified case-crossover study

BACKGROUND: A number of epidemiological studies have been conducted to research the adverse effects of air pollution on mortality and morbidity. Hypertension is the most important risk factor for cardiovascular mortality. However, few previous studies have examined the relationship between gaseous air pollution and morbidity for hypertension. METHODS: Daily data on emergency hospital visits (EHVs) for hypertension were collected from the Peking University Third Hospital. Daily data on gaseous air pollutants (sulfur dioxide (SO(2)) and nitrogen dioxide (NO(2))) and particulate matter less than 10 μm in aerodynamic diameter (PM(10)) were collected from the Beijing Municipal Environmental Monitoring Center. A time-stratified case-crossover design was conducted to evaluate the relationship between urban gaseous air pollution and EHVs for hypertension. Temperature and relative humidity were controlled for. RESULTS: In the single air pollutant models, a 10 μg/m(3 )increase in SO(2 )and NO(2 )were significantly associated with EHVs for hypertension. The odds ratios (ORs) were 1.037 (95% confidence interval (CI): 1.004-1.071) for SO(2 )at lag 0 day, and 1.101 (95% CI: 1.038-1.168) for NO(2 )at lag 3 day. After controlling for PM(10), the ORs associated with SO(2 )and NO(2 )were 1.025 (95% CI: 0.987-1.065) and 1.114 (95% CI: 1.037-1.195), respectively. CONCLUSION: Elevated urban gaseous air pollution was associated with increased EHVs for hypertension in Beijing, China.