Asthma rates higher among over-50s living in areas with more local air pollution

Researchers today published a study showing that over-50s in Ireland living in areas with higher levels of air pollution are more likely to have asthma. The study, published in the International Journal of Epidemiology, was carried out by a team from ESRI, TCD, RCSI, TU Dublin and IT Carlow. The study linked health data from 8,162 participants in The Irish Longitudinal Study on Ageing (TILDA) to estimates of annual average nitrogen dioxide (NO2) concentrations near their homes. NO2 is an air pollutant associated mainly with road transport sources such as cars, trucks and buses. Those living in areas with higher NO2 concentrations had significantly higher rates of asthma.

The researchers carried out a statistical analysis of the data, controlling for many personal characteristics that might affect asthma risk, such as age, sex, income and history of smoking. Two methods of identifying those with asthma were used, giving similar results: participants were asked if they had ever had a diagnosis of asthma and the study checked if they were using any asthma medications (such as inhalers).

Overall, 9 per cent of the sample aged 50+ reported an asthma diagnosis, and 6.9 per cent reported using relevant medications (such as inhalers). Living in an area with higher NO2 concentrations was found to be associated with an increased probability of asthma. For example, a 1 part per billion (ppb) increase in local NO2 was associated with a 0.24 percentage point increase in the probability of reporting an asthma diagnosis, and the effect size was similar for the probability of using asthma medication (0.21 percentage points). To put these results in context, the average exposure to NO2 in this sample was 4.8ppb, with 95 per cent of the sample exposed to NO2 levels below 13 ppb.

Asthma affects over 300 million people worldwide, making it the most common chronic respiratory condition. Previous research on asthma and air pollution has focused on the risk to children. There has been less evidence of possible risks to older people. More research will be needed to show if air pollution causes asthma or makes it more severe for older groups, but these results are suggestive that there might be such links.

One of the team, Professor Margaret O’Mahony from TCD, said “the results demonstrate the importance of research on the health impacts of air pollution and we would recommend more investment in both health and air pollution data collection to improve our knowledge of these effects.”

Dr Anne Nolan from ESRI said “Ireland has good air quality compared to many other countries, but the study found higher levels of asthma among people exposed to even relatively small increases in NO2.”

Acknowledgement

This project was funded under the EPA Research Programme 2014-2020. The EPA Research Programme is a Government of Ireland initiative funded by the Department of Communications, Climate Action and Environment. It is administered by the Environmental Protection Agency, which has the statutory function of co-ordinating and promoting environmental research.

The Irish Longitudinal Study on Ageing (TILDA), Trinity College Dublin, is a nationally representative study of people age 50 and over in Ireland. TILDA is funded by the Department of Health, The Atlantic Philanthropies and Irish Life.

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