Springtime asthma hospitalizations and pollen levels: Are they related?

Abstract

In this ecological study hospital emergency admissions in London, Ontario were examined during the peak spring months of the years 1983-88 to determine if asthma morbidity was associated with tree and grass pollen levels. Pollutants and weather factors were also analyzed because they may have confounded the association between asthma and pollen, or may have had their effect modified by pollen. Daily and weekly asthma admissions were associated significantly with tree pollen (r$\sb{\rm s}$ = 0.12 and 0.25 respectively) and total pollen (tree + grass) counts (r$\sb{\rm s}$ = 0.12 and 0.34 respectively) but not with grass pollen alone. The same associations were found using ANOVA after the pollen was categorized into quartiles. These associations stood-up after controlling for confounders. A negative associations of asthma admissions was also found with temperature and this became stronger when pollen counts were elevated. Although negative associations were found for asthma with NO$\sb3$ and SO$\sb4$, these associations are not plausible and may be due to confounding by temperature. The ecological nature of this study prevented ascertainment of exposure and precluded controlling other potential confounders. (Abstract shortened by UMI.)