Asthma Exacerbations Seasonal Variation in Two Perennial Phenotypes during Twenty Years (1995-2014): House Dust Mite Monosensitized and Non Atopic Patients

Background: Asthma exacerbations (AE) are caused for a variety of reasons including unrecognized disease, undertreated or unresponsive to conventional therapy asthma, recent exposure to triggers like viruses, usually rhinovirus or allergens. AE is defined as a worsening of asthma sufficient to require medical intervention and usually administration of oral steroids reflected objectively as a fall of PEF, FEV1 ≥20% or 30%. This study was performed to investigate the epidemics of exacerbations in mites monosensitized asthmatics. Seasonal variability of AE in such patients could be used as a tool for a convenient and preventive management. Non atopic asthmatic patients were used as a control group and this way we could understand how important trigger is the allergen comparing to virus. 

Methods: We have studied, from 1995 to 2014, AE in patients suffering from these two different phenotypes of asthma. Seasonal variation of AE in each phenotype separately and consequently comparison of them were evaluated by applying the x² –test and the null hypothesis. The null hypothesis is that there is not difference in the number of AE occurred in each month of the year.

Results:  

Mite monosensitized patients (Month/AE number): Jan / 32, Feb / 41, Mar / 58, Apr / 59, May / 74, Jun / 55, Jul / 37, Aug / 10, Sep / 73, Oct / 67, Nov / 54, Dec / 30.    

 By applying the χ2-test for 11 d.f we obtained χ2=84,319 (P-value<0,0001). Therefore the null hypothesis is not accepted and there is statistical significant difference in the number of AE occurred during the year (higher in spring and autumn months).

 Non atopic patients (Month/AE): Jan / 249, Feb / 239, Mar / 245, Apr / 237, May / 194, Jun/ 173, Jul / 124, Aug / 69, Sep / 249, Oct / 309, Nov / 283, Dec / 214  

  By applying the χ2-test for 11 d.f we obtained χ2=229,940 (P-value<0,0001). Therefore the null hypothesis is not accepted and there is statistical significant difference in the number of AE occurred during the year (higher in spring and winter months).

Comparison of both time distributions revealed significant difference between them, χ2=62.042 and P-value<0.0

Conclusions: Our results showed that in Greece during 20 years (from 1995 to 2014) AE are seasonal variable in non atopic and mites monosensitized asthmatics but different between them. The results indicate that atopics react to viruses in a different way comparing to non atopics.