Asthma in Over-50s in Ireland

Asthma affects over 300 million people worldwide, and is the world’s most common chronic respiratory condition. New collaborative research sheds insight highlighting how older adults who live in areas with higher levels of air pollution are more likely to have asthma.

Researchers have 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. Those living in areas with higher NO2 concentrations had significantly higher rates of asthma.

Asthma affects over 300 million people worldwide. A growing body of research suggests that air pollution can contribute to the risk of developing asthma and the severity of the condition for those who suffer from it. However, the evidence of links between local air pollution and asthma is stronger for young people than for older adults. In this paper, the authors examined whether asthma rates are higher among over-50s in Ireland who live in areas with higher levels of local nitrogen dioxide (NO2) air pollution. NO2 is one of several pollutants emitted by motor vehicles, and it is often used as an indicator of transportrelated air pollution more generally.

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.

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.

“Our study adds to the evidence that there is an association between NO2 exposure and asthma among older adults, a group for which pollution exposures have received less research attention than younger people. The study used a novel approach to identify asthma cases, taking account of both respondents’ own reports of having asthma and separate evidence on their use of relevant medications. The results using the two methods were similar,” said the authors.

“Although levels of air pollution are relatively low in Ireland compared to many other countries and standard regulatory limits are rarely exceeded, we still found significant links between pollution and asthma rates. Finally, the individual-level data used in this study allowed us to control for many socioeconomic factors that might influence asthma rates and lead to misleading results if they were not taken into account.”

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.”

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