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Asthma among individuals hospitalized for influenza is more common among women. These patients have favorable clinical outcomes and mild serum inflammatory response, according to a study recently published in European Respiratory Journal.
This study included 133 adults hospitalized with influenza like symptoms, 30.1% (n=40) of whom had asthma. Recruitment took place between 2009 and 2011 in 9 hospitals in England. Data including prescription records, asthma diagnosis, and medical history were obtained for all participants; those with potentially confounding comorbidities were categorized as not having asthma. Respiratory illness was graded from 1 to 3 for severity, and severe outcome was defined as mortality or invasive ventilation.
Serum and nasal samples from 36 healthy controls were assessed for comparison. The chi-squared test, Fisher’s exact test, unpaired t-test, and 2-tailed Mann Whitney tests were used to compare clinical features between those with and without asthma, whereas the Kruskal-Wallis and Dunn’s test were used to compare mediators. The association between asthma and severe outcome was investigated through logistic regression.
Compared with those without asthma, patients with asthma were significantly more likely to be women (70% vs 38.7%; odds ratio [OR] 3.69; 95% CI, 1.67-8.18; P =.0012), had a shorter length of hospitalization (8.3±2.55 vs 15.3±1.82 days), and were less likely to need intubation during peak severity (15% vs 37.6%; P =.0338). The majority of cases were caused by influenza A (95%; n=38), with influenza B responsible for just 2 (5%) cases.
Among those without asthma, presenting to the hospital more than 4 days after the onset of symptoms (OR 5.49; 95% CI, 2.28-14.03; P =.0002) and receiving inhaled corticosteroids (OR 2.625; 95% CI, 1.02-6.96; P =.0466) were associated with a greater likelihood of severe outcome. Compared with those without asthma, patients with asthma showed lower systemic inflammation in the first day of hospitalization, characterized by lower tumor necrosis factor-α (P <.0001), C-C motif chemokine ligand 2 (P =.0038), C-X-C motif chemokine ligand 8 (P <.0001), C-X-C motif chemokine ligand 9 (P =.0031), interleukin (IL)-6 (P =.0005), IL-10 (P =.0411), and IL-17 (P =.0197).
Total immunoglobulin E (IgE), serum IL-13, blood eosinophil gene expression levels, and neutrophils were similar between groups. Those with asthma were likelier than those without asthma to have received the influenza vaccine (37.5% vs 18.3%; P =.0261).
Limitations to this study include its design, which was aimed at all influenza patients instead of those with pre-existing asthma; a lack of certain spirometric data and other information, exhaled breath nitric oxide, blood eosinophil counts, or sputum cell counts; and a 40% inhaled corticosteroid use among the included population.
The study researchers concluded that individuals with asthma “hospitalized with influenza are predominantly female and have a good prognosis, with reduced systemic inflammation but comparable mucosal responses to individuals without asthma.” Those with and without asthma show statistically similar nasal IL-5 and IL-13 levels and serum total IgE levels. Assessing the individual’s systemic host immune and airway mucosal response to influenza is recommended.
Disclosure
Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.
Reference
Jha A, Dunning J, Tunstall T, et al; MOSAIC Investigators. Patterns of systemic and local inflammation in patients with asthma hospitalised with influenza [published online August 7, 2019]. Eur Respir J. doi: 10.1183/13993003.00949-2019
