Association between airborne pollen and epidemic asthma in Madrid, Spain: a case-control study

Abstract

Background Despite the fact that airborne pollen is an important factor in precipitating asthma attacks, its implication in increases of epidemic asthma in usual meteorological conditions has not been reported. A study was undertaken to estimate the relationship between various types of aeroallergens and seasonal epidemic asthma in the region of Madrid, Spain. Methods A caseecontrol study was carried out in individuals aged 4e79 years who received emergency healthcare for asthma during 2001 in a base hospital covering a population of 750 000 inhabitants of Madrid. A skin prick test was performed with grass pollen, plantain pollen, olive pollen, cypress pollen, plane tree pollen, dust mites and Alternaria and the prevalence of skin reactivity was compared between subjects with asthma requiring emergency care for asthma within (cases) and outside (controls) the seasonal epidemic period. Data were analysed using logistic regression adjusting for age and sex. Results The response rate was 61.7% for cases (n¼95) and 51.6% for controls (n¼146). The OR of sensitisation to grass pollen for cases compared with controls was 9.9 (95% CI 4.5 to 21.5); plantain pollen: 4.5 (95% CI 2.5 to 8.2); olive pollen: 7.3 (95% CI 3.5 to 15.2); plane tree pollen: 3.6 (95% CI 2.0 to 6.4); cypress pollen: 3.5 (95% CI 2.0 to 6.2); dust mites: 1.1 (95% CI 0.6 to 1.9); Alternaria: 0.9 (95% CI 0.5 to 1.9). The association with grasses was maintained after adjusting simultaneously for the remaining aeroallergens (OR 5.0 (95% CI 1.5 to 16.4)); this was the only one that retained statistical significance (p¼0.007). Conclusions These results suggest that allergy to pollen, particularly grass pollen, is associated with the epidemic increase in asthma episodes during the months of May and June in the Madrid area of Spain.

The role of seasonal grass pollen on childhood asthma emergency department presentations

“…Using statistical techniques to account for non‐linearity in the relationship between grass pollen counts and asthma hospital admissions by adults, we were the first to find this association was linear at first and reached a plateau at about 30 grains/m 3 . Our findings were replicated in a study of a group of adult asthmatics by Galan and colleagues . However, the relationship between grass pollen counts and asthma exacerbations in children has not been as rigorously investigated.…”

“…To the best of our knowledge, this is the first study to report a dose‐response effect of grass pollen on asthma ED presentations in children. The only studies that have examined these effects in relation to pollen and emergency department presentations looked at mixed age groups of adults and children . Tobias et al.…”

The influence of sensitisation to pollens and moulds on seasonal variations in asthma attacks

“…There may be more thunderstorms, which are known to cause sudden peaks in grass and mould allergen levels and “epidemic asthma” in those who are sensitised [11, 38]. This report provides baseline information showing that those who are sensitised are indeed a subgroup of the population who will be particularly at risk if these climatic changes occur.…”

“…Small panel studies suggest asthma severity is worse in the pollen season in those sensitised to grass [8, 9] and in winter in those sensitised to house dust mite [10]. Asthmatics presenting to accident and emergency departments in Spain in early summer (May–June) were more likely to be sensitised to grass than those presenting in other months [11]. Similarly, mild, near fatal and fatal asthma has been associated with sensitisation to Alternaria in months where Alternaria levels are high [12, 13].…”

Decline in Asthma Prevalence and Severity in Israel over a 10-Year Period

“…Since 1995 however, the prevalence of asthma and its related morbidity and mortality appears to have plateaued and may even have decreased in some western countries [3,4,5,6]. The reasons for the changes in trends of asthma prevalence and severity are probably multiple [3] and may theoretically have involved improved access to appropriate medical care, increasing use of inhaled corticosteroids (ICS) [7], changes in outdoor air pollution levels [8], reduced active and passive exposure to tobacco smoke [9,10,11,12,13], and reduced concentrations of airborne pollen allergens [14,15,16,17]. …”