Trends in mortality show an increase in all adult age groups followed by a gradual decline. Neither the introduction of a revised interpretation of Rule 3 in 1984 (a rule advising how to select the cause of death, see factsheet 97/3) nor its withdrawal in 1993 were associated with substantial step changes across any age groups. This is indicative of a lack of any coding effect.

Mortality is related to incidence (cases and exacerbations), severity and case fatality. Thus, the mortality trends could represent changes in either the epidemiology or medical care of asthma. It is tempting to speculate that the downturn in admissions and mortality is due to improved management of asthma, but an underlying change in epidemiology due to trends in unknown factors is also possible.