Most patients with asthma will not experience an exacerbation
medwireNews: Only a third of patients with asthma will experience an exacerbation, show 7 years of observation in more than 50,000 adults with the condition.
“Our findings suggest that the majority of asthma patients will seldom exacerbate and that when patients do exacerbate, half of the time it will be a single sporadic event,” say Chloe Bloom (Imperial College London, UK) and co-researchers.
“However, in the other half, having an exacerbation is one of the biggest risk factors for having a subsequent one, even up to 5 years earlier.”
The team studied exacerbation patterns over a continuous follow-up spanning 7 years in 51,462 adults aged 18 to 55 years with varying asthma severity and treatment levels.
The majority of patients, at 64%, did not experience any exacerbations, and 24% had only one exacerbation. The percentage of patients experiencing frequent exacerbations, at seven or more, was below 5%.
Among the 18,555 patients who experienced exacerbations, 51% demonstrated a sporadic pattern, experiencing exacerbations only in a single year, whereas the remaining 49% showed a recurrent pattern over multiple years, including about 2% who experienced exacerbations every year of the follow-up, characteristic of a frequent-exacerbator pattern.
“The number of patients who did not exacerbate, or displayed only a sporadic pattern, decreased with increasing asthma severity; the opposite was found for those who displayed a recurrent pattern, or had a frequent-exacerbator phenotype,” the researchers report in the American Journal of Respiratory and Critical Care Medicine.
A number of patient characteristics were associated with exacerbations, including the need for more intensive medication, having comorbid chronic obstructive pulmonary disorder, having an elevated eosinophil count, being aged between 35 and 55 years, being female, and being a current smoker.
These risk factors were more strongly associated with recurrent than sporadic exacerbations, whereas there were no “clear differences in specific patient demographics or clinical characteristics” between patients who did and did not have exacerbations, the team comments.
“These findings confirm the unpredictable nature of asthma exacerbations, regardless of disease severity, that patients and physicians see every day,” the researchers add.
A patient’s history of exacerbation was the strongest risk factor for a future one, say Bloom and colleagues, and this included both a recent and distant (more than 1 year ago) exacerbation history.
They found that exacerbations experienced 5 years ago still carried a significant 2.6-fold increased risk for a future exacerbation, although the risk decreased beyond 5 years. For a history of exacerbations in the past 2 years and 1 year, the risk for future exacerbations increased 3.8- and 6.7-fold, respectively.
“Both a recent and distant history of multiple exacerbations during one year conferred a higher risk than a single exacerbation in that year,” note the researchers. “In contrast, and possibly less intuitively, only the severity of a recent exacerbation had a significant effect on the risk of a future exacerbation; the severity of a distant exacerbation had no significant effect.”
By Lucy Piper
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