Asthma phenotypes change with age
medwireNews: Researchers have found that older patients with asthma have different phenotypes to those of younger patients.
Specifically, the results, published in Respirology, show that patients of 65 years or older have a lower odds of atopic and eosinophilic asthma than their peers aged 40 years or younger, whereas they have higher odds of irreversible airway obstruction and severe asthma.
“Ageing of the immune system and differences in environmental exposures throughout life are possible explanations for the association between age and certain asthma phenotypes,” say Eduardo Ponte (Jundiaí Medical School, São Paulo, Brazil) and team.
Environmental exposures found to be more common in older than younger participants were vaginal birth delivery, history of breastfeeding, living in a rural area, having more siblings, and a history of tuberculosis.
Inhaled corticosteroid dose and comorbidities, including diabetes and hypertension, were adjusted for and did not bias the associations, the researchers note.
A total of 2099 asthma patients were screened – 1393 from primary care and 706 from secondary care – 868 of whom were included in the analysis.
The odds of having the irreversible airway obstruction asthma phenotype was increased a significant 3.45-fold (95% confidence interval [CI]: 2.12–5.60) among the 91 patients aged 65 years and older, compared with the 347 patients aged 40 years and younger. The 430 patients in the 41–64 year age group also had a significantly increased risk, although to a lesser degree at 1.83-fold (95% CI: 1.32–2.54).
The odds of having severe asthma phenotypes were increased 4.55-fold (95% CI: 2.39–8.67) and 3.23-fold (95% CI: 2.26–4.62), among patients aged 65 years and older and 41–64 years, respectively, compared with their younger peers.
By contrast, the odds ratios for the atopic phenotype were significantly reduced, at 0.47 (95% CI: 0.27–0.84) and 0.56 (95% CI: 0.39–0.79) for those aged 65 years and above and 41–64 years, respectively, while the corresponding odds ratios for the eosinophilic phenotype were 0.39 (95% CI: 0.24–0.64) and 0.63 (95% CI: 0.46–0.84).
Ponte and colleagues point out that the association between age and asthma phenotypes was unaffected by a higher frequency of late-onset asthma in the older group of patients, with the associations retained when only patients with early-onset asthma were assessed.
In a related editorial, Rodrigo Athanazio and Alberto Cukier, both from the University of São Paulo, comment that the age–phenotype associations reported in the current study depict a group of elderly patients who “are recognized as less likely to respond to existing anti-inflammatory therapies,” and add: “These results challenge us to seek new interventions.”
They say: “It is important to remember that asthmatic patients over 65 years are consistently excluded from large clinical trials; Ponte et al have highlighted the need to evaluate the particular (potential?) benefit of agents such as long-acting muscarinic agents, xanthines, thermoplasty or even new therapeutic targets that may have positive effects in this underserved population.”
By Lucy Piper
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