Adult asthma has more than doubled in 20 years

Asthma in adults has more than doubled in the last twenty years, says new research conducted in Scotland and published in the British Medical Journal (BMJ). The research suggests that the increase may be due reactions to environmental allergens.

Though increases in asthma in children and university students over the past few decades is well documented, this study, conducted in Renfrew and Paisley, is the first to investigate increases in adult asthma. With no medical test for asthma, the study was carried out by a questionnaire survey, in 1972-6 and 1996, asking respondents about respiratory symptoms.

In people who have never smoked, the numbers suffering from asthma and hay fever increased from 3% and 5.8% respectively to 8.2% and 19.9%. Though symptoms have changed little in people who smoke, the actual numbers of both male and female smokers halved between the surveys. The big increase occurred in those whose asthma is associated with hay fever.

“Our paper, and the work of others, suggests that it is the increased prevalence of atopy that is driving the increased prevalence of asthma,” Dr Mark Upton, one of the researchers told edie. “Atopy is the tendency to mount an allergic response to environmental allergens such as house-dust mite faeces, cat dander, [and] grass pollen. Atopic disorders include hay fever, eczema, urticaria, and some, but not all, asthma.”

Childhood asthma may persist into, or recur in, adulthood, say the researchers, leading them to expect this increase in adult asthma as increasing numbers of children affected by asthma become older. However, it is not known why asthma is on the increase, says Dr Upton.

The researchers emphasise that the study suggests that the increase in atopic asthma is not due to the respondents having an increased awareness of how to diagnose asthma, though it may account for the increase in non-atopic asthma. He is also confident that due to the timescale, the increase is not genetic.

From the research it is not possible to say whether this increase is a fair representation of the frequency of asthma in general, says Dr Upton.

“Given this variation in point prevalence – i.e. at one point in time – it is at least plausible that there is geographical variation in the environmental factors responsible for the changes over time in prevalence,” said Dr Upton. “Besides variation between countries, the ECRHS [European Respiratory Health Survey] has even documented large variations in point prevalence of asthma within a country. Therefore we must be careful about extrapolating too far.”

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