During the 5.5-year study period, 1939 patients (931 males and 1008 females, age range 2 to 106 years, mean age 44.22 ± 26.16 years) were admitted for asthma exacerbation to one of the four participating hospitals. About one fifth of the patients (416, 21.5%) were younger than 18 years, and 457 (23.5%) were older than 65 years. The number of daily admissions varied from zero to 13. The patients were hospitalized for periods ranging from 1 day to 1 month (average 4.7 days).
There is growing epidemiological evidence of associations between air pollution and respiratory disorders in
| O3 (ppm) | CO (ppm) | NO2 (ppm) | SO2 (ppm) | PM10 (µg/m3) | Year |
|---|---|---|---|---|---|
| 0.010 ± 0.006 0.001 0.033 0.085 218 0.06 | 5.343 ± 1.482 1.617 9.063 2.01 218 0.32 | 0.026 ± 0.005 0.013 0.043 0.006 218 0.06 | 0.183 ± 0.031 0.129 0.254 0.051 218 0.13 | 89.218 ± 47.48 13.1 331.3 50.36 218 0.01 | 2007 Mean ± SD Min Max Interquartile range Annual admissions P-value |
| 0.010 ± 0.006 0.001 0.07 0.008 417 0.00 | 4.338 ± 1.087 1.482 8.134 1.477 417 0.20 | 0.022 ± 0.004 0.002 0.034 0.007 417 0.01 | 0.232 ± 0.057 0.148 0.393 0.108 417 0.001 | 102.66 ± 97.50 21.29 966.5 55.17 417 0.06 | 2008 Mean ± SD Min Max Interquartile range Annual admissions P-value |
| 0.013 ± 0.007 0.003 0.099 0.01 360 0.005 | 1.189 ± 0.862 1.189 5.731 0.726 366 0.03 | 0.026 ± 0.007 0.005 0.074 0.008 360 0.35 | 0.057 ± 0.092 0.005 0.36 0.01 366 0.07 | 115.68 ± 86.00 23.97 980 96.49 366 0.4 | 2009 Mean ± SD Min Max Interquartile range Annual admissions P-value |
| 0.015 ± 0.007 0.005 0.061 0.011 338 0.00 | 2.689 ± 1.007 0.94 6.60 1.16 338 0.00 | 0.046 ± 0.014 0.013 0.082 0.018 338 0.003 | 0.011 ± 0.003 0.003 0.022 0.004 338 0.12 | 96.70 ± 61.22 34 698.6 96.49 338 0.28 | 2010 Mean ± SD Min Max Interquartile range Annual admissions P-value |
| 0.026 ± 0.012 0.006 0.077 0.014 454 0.01 | 1.747 ± 0.681 0.403 5.12 0.073 454 0.12 | 0.018 ± 0.009 0.004 0.073 0.005 454 0.21 | 0.005 ± 0.003 0.001 0.016 0.004 454 0.38 | 109.812 ± 52.747 18 425.5 50.11 454 0.33 | 2011 Mean ± SD Min Max Interquartile range Annual admissions P-value |
| 0.031 ± 0.010 0.015 0.061 0.014 163 0.09 | 1.447 ± 0.455 0.371 2.674 0.69 163 0.23 | 0.014 ± 0.002 0.008 0.018 0.003 163 0.36 | 0.003 ± 0.002 0.001 0.009 0.002 163 0.21 | 148.329 ± 180.02 24.74 1901 81.90 163 0.11 | first 6 months of 2012 Mean ± SD Min Max Interquartile range Annual admissions P-value |
| 0.01 ± 0.01 0.001 0.099 0.013 1939 0.03 | 3.25 ± 1.67 0.37 9.06 2.48 1939 0.06 | 0.026 ± 0.01 .002 0.082 0.004 1939 0.00 | 0.092 ± 0.1 0.001 0.393 0.17 1939 0.005 | 106.86 ± 88.62 13.10 1901 60.59 1939 0.06 | 2007 till mid-2012 Mean ± SD Min Max Interquartile range Total admissions P-value |
PM10, particulate matter ≤10 µm in diameter; SO2, sulfur dioxide; NO2, nitrogen dioxide; CO, carbon monoxide; O3, ozone. *, significant correlation (2-tailed P-value < 0.05).
developing countries [
The possible effects of NO2 in the air include increased sensitivity to respiratory viral infections and enhanced reactions to allergens (e.g., house dust mites), which exacerbates asthma and reduces lung function in children [
other studies in Iran [
Ozone is an air pollutant related to sunlight. Because of the warm climate in our area, O3 concentration is high. Prolonged lung injury, oxidative stress, macrophage accumulation and extensive abnormal lung function have been reported in mice that inhaled O3 [
Coal is still used as the main source of energy in some parts of Asia. The burning of coal emits a considerable amount of SO2 which increases bronchoconstriction in patients with asthma. We found a positive relationship between SO2 level and hospital admissions for asthma attack, which is in consistent with other reports from Iran and Turkey [
Among air pollutants, particulate matter has the greatest effects on human health [
Carbon monoxide, a marker of vehicle traffic, is a product of incomplete combustion of carbon-containing fuel. During the period covered by our study there were no reports of CO levels ≥ 9 ppm, the level considered toxic according to National Ambient Air Quality Standards (NAAQS) [
An analysis of the relationship between seasonal variations in asthma incidence and air pollutants in Taiwan showed strong associations with PM10, O3 and SO2 in children [
Admission rates for patients with asthma are usually higher during cold seasons, which may be explained by the exacerbations of asthma after viral infections [
The stationary R-squared value and goodness-of-fit for the ARIMA model to predict monthly admissions were 0.523 and 0.62, respectively. Based on our data, we predicted an increasing trend in monthly mean levels of air pollutants and numbers of patient admissions to 2015 (
Many studies suggest that the prevalence of asthma has reached a plateau or may be declining in developed countries, whereas it continues to increase in Asian countries. A factor that may be related to these opposing trends is that economic development in Asia is supported by the increased use of fossil fuels?which contribute to air pollution?as energy sources. On the basis of our data, we predicate that air pollution and asthma admission rates will be a major problem in 2015 in our region.
In this study we did not measure temperature, humidity and indoor allergens, all of which, along with air pollution, can affect asthma exacerbations. We recorded admission rates of patients with asthma at university hospitals only, and did not obtain data from private clinics and hospitals that also manage patients with asthma attacks in our region. Generally, different air pollutants interact with each other and an exact quantitation of each pollutant is rarely possible. The effect of air pollutants on asthma is likely to be a chronic process, and delayed
outcomes may appear long after exposure. Another potential limitation of this study is that we did not obtain follow-up data for our sample of patients later than mid-2012. We were not able to measure the concentration of PM2.5, and cannot speculate on the possible relationship between the levels of particles smaller than PM10 and hospital admissions for asthma in our setting.