The epidemic of asthma has peaked, a study has suggested. According to research led by Dr Douglas Fleming (Royal College of General Practitioners, Birmingham) the number of new asthma episodes presented to general practitioners has gradually declined, following an increase in incidence between 1989 and 1993.
Data were recorded weekly between January, 1989, and December, 1998. The researchers found that the pattern of increase followed by reduction in incidence of new attacks or exacerbations was evident in all age groups (both adults and children), during all seasons and in all the regions throughout England and Wales. Similar trends were seen for acute bronchitis.
The occurrence of downward trends in asthma and bronchitis in these three areas at nearly the same time (a few months apart), showed that the findings could not be linked to changes in factors previously considered to be responsible for the increase in asthma. The authors comment that winters have been less severe in recent years, but most of the trends reported were evident throughout the year. They also say that the trend cannot be explained by changes in the patterns of health care usage and they found no temporal association with changes in treatment (Thorax 2000;55:657).
Dr Fleming told The Journal on July 18 that the reduction was as mysterious as the increase in the number of asthma episodes had been in the late 1980s. He said that the reduction in asthma could not be explained on the basis of alternative diagnosis as acute bronchitis, since incidence of acute bronchitis also decreased.
In another recent study, Dr Mark Upton (University of Glasgow) and colleagues found that the prevalence of asthma in two generations of adults increased two-fold in 20 years, between 1976 and 1996, irrespective of smoking (British Medical Journal 2000;321:88). They suggested that the increase was largely associated with trends in atopy, as measured indirectly by the prevalence of hay fever.
Dr Fleming, commenting on this study, said that it would be unlikely that prevalence would continue to rise if at the same time the number of new attacks was going down.