Asthma deaths in a large provincial health system. A 10-year population-based study.

Rationale: Individuals with asthma are more likely to die from chronic conditions than the general population. Measuring only mortality with asthma listed as the primary cause of death may lead to an underestimation of total asthma mortality.
Objectives: To examine mortality patterns in the asthma population over 10 years, including asthma as the primary cause of death (asthma-specific mortality) and asthma as a secondary, contributing cause of death (asthma-contributing mortality).
Methods: Health administrative data from Ontario, Canada were used to identify mortality rates and cause of death in subjects 0 to 99 years of age. Mortality rates were calculated in the asthma and general population from 1999 to 2008. Total asthma mortality was estimated by adding rates of asthma-specific and asthma-contributing mortality for years 2003 to 2008.
Measurements and Main Results: Asthma-specific mortality rates per 100,000 asthma population decreased by 54.4% from 13.6 in 1999 to 6.2 in 2008. In 2008, the asthma population had higher all-cause mortality compared with the general population (rate ratio, 1.3), asthma-specific mortality rates were 60% higher among those in the lowest compared with highest socioeconomic status, and total asthma mortality was fourfold higher than asthma-specific mortality alone (21.6 vs. 5.4 per 100,000).
Conclusions: All-cause mortality rates have decreased substantially over the past decade. Compared with the general population, the asthma population has higher all-cause mortality and is more likely to die from comorbid conditions. Total asthma mortality was fourfold higher than asthma-specific mortality, highlighting the importance of comprehensive measurement approaches that include asthma-specific and asthma-contributing mortality.