Air pollution and asthma control in the Epidemiological study on the Genetics and Environment of Asthma

Abstract

Background: The associations between exposure to air pollution and asthma control are not well known. The objective of this study was to assess the association between long-term exposure to NO(2), O(3) and PM(10) and asthma control in the follow-up of the Epidemiological study on the Genetics and Environment of Asthma (EGEA2) (2003-2007).

Methods: Modelled outdoor NO(2), O(3) and PM(10) estimates were linked to each residential address using the 4 km grid air pollutant surface developed by the French Institute of Environment in 2004. Asthma control was assessed in 481 subjects with current asthma using a multidimensional approach following the 2006-2009 Global Initiative for Asthma guidelines. Multinomial and ordinal logistic regressions were conducted adjusted for sex, age, body mass index, education, smoking and use of inhaled corticosteroids. The association between air pollution and the three domains of asthma control (symptoms, exacerbations and lung function) was assessed. ORs are reported per IQR.

Results: Median concentrations (in micrograms per cubic metre) were 32 (IQR 25-38) for NO(2) (n=465), 46 (41-52) for O(3) and 21 (18-21) for PM(10) (n=481). In total, 44%, 29% and 27% had controlled, partly controlled and uncontrolled asthma, respectively. The ordinal ORs for O(3) and PM(10) with asthma control were 1.69 (95% CI 1.22 to 2.34) and 1.35 (95% CI 1.13 to 1.64), respectively. When including both pollutants in the same model, both associations persisted. Associations were not modified by sex, smoking status, use of inhaled corticosteroids, atopy, season of examination or body mass index. Both pollutants were associated with each of the three main domains of control.

Conclusions: The results suggest that long-term exposure to PM(10) and O(3) is associated with uncontrolled asthma in adults, defined by symptoms, exacerbations and lung function.

Figure 1

Flow chart of the EGEA population included in this analysis

Figure 2

Sensitivity analysis results. Odds ratios (ORs) and 95% confidence intervals (from ordinal regression) showing the associations between each IQR of modelled O_3-sum a) and PM₁₀ b) and controlled asthma * Non-movers are those who had been living for at least two years at the same address in 2004 (thus is those who have not moved since 2002)

Figure 2

Sensitivity analysis results. Odds ratios (ORs) and 95% confidence intervals (from ordinal regression) showing the associations between each IQR of modelled O_3-sum a) and PM₁₀ b) and controlled asthma * Non-movers are those who had been living for at least two years at the same address in 2004 (thus is those who have not moved since 2002)