Population-attributable fraction for occupation and asthma

Abstract

Here we review the use of the concept of population-attributable risk (PAR) of asthma associated with occupation and give the context for its interpretation. For asthma there is major interest in delineating the ``burden of disease{''}, because such assessments can inform health care priorities, intervention policies, and assessment of impact once such steps are implemented. For asthma, the burden of disease from occupational factors is of particular relevance because asthma is a common disease that affects persons of working age and because asthma can be associated with major morbidity and economic cost. In 1999, we carried out a systematic review of the published literature relevant to the occupational PAR in asthma. Of 23 published PAR estimates identified, the median value was 9%, but among those, the 10 estimates based on population-based studies yielded a median PAR estimate of 15%. A few years later a task force of the American Thoracic Society (ATS) summarized the general population-based studies in this field, ending up with a median value of 15%. We have summarized data from publications that have appeared since 2000 and the median value from these publications is 14.4% (range 6-31%). We show in this analysis that 3 in 20 cases of asthma among adults are likely to be linked to occupational factors. Longitudinal incidence-based estimates, which should be the most reliable, suggest that, if anything, the actual PAR may even be higher. Other measures such as impaired quality of life and economic disadvantage are also important, but are not addressed in this review as there is lack of studies. This points to future research needs to address this knowledge gap in the field of work-related asthma. In the meantime, the consistency of the PAR data that we do have certainly underscores the importance of workplace factors in the overall burden of asthma.