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Trends in mortality show two waves, seen to some extent in all age groups (note the difference in scale in the two graphs however). The first occurred in the 1960s and a second rise occurred from the 1970s until the late 1980s. Annual rates have tended to slowly fall since then though in children there is some random variability due to the small numbers of childhood asthma deaths. There is little evidence of major step changes associated with successive ICD revisions except following the implementation of ICD 9 in 1979 when there was an increase of 28%, mainly in older age groups. 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 mortality is due to improved management of asthma, but an underlying change in epidemiology due to trends in unknown factors is also possible.
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