Fungal and other spore counts as predictors of admissions for asthma in the Trent region

Objectives-The importance of airborne fungal and other spores in provoking asthma attacks is uncertain. Panel studies have generated evidence that sug gests a link between outdoor spore counts and severity of asthma. There hav e been no population based time series studies relating outdoor exposure to spores with incidence of attacks of asthma. Methods-Outcomes were hospital admissions for asthma on 2002 days during 19 87-94, for children and adults in the Trent region of England. Predictors w ere daily counts of 25 spore taxa from volumetric traps in Derby on the sam e and previous day. Admissions for asthma were adjusted for weekly, seasona l, and longer term trends by log linear autoregressive models. Spore counts on 6 days of asthma epidemics were also examined. Results-When spore counts for individual taxa were analysed as quantitative variables, two positive and two negative correlations (out of a possible 1 00) were significant at the 5% level. When spore counts were dichotomised a t the 90th percentile, one negative and eight positive correlations (out of 100) were significant at the 5% level. All significantly positive associat ions related to admissions among children, but none involved the total spor e count. However, total spores were above the 90th percentile on four of th e six epidemic days (odds ratio (OR) 9.92, 95% confidence interval (95% CI) 1.41 to 109.84), but epidemics occurred on only four of 343 days with high total moulds. Conclusions There was some evidence that exceptional rates of admission for asthma tend to occur on days with high total mould spore counts, but no sp ecific taxon was consistently implicated. The predictive power was insuffic ient to support a public warning system.