Marked seasonal variation in COPD exacerbations

By Mark Cowen, Senior medwireNews Reporter

Patients with chronic obstructive pulmonary disease (COPD) are significantly more likely to experience exacerbations during the winter than summer months, research shows.

The team also found that the proportion of exacerbations treated with antibiotics was higher during the winter (December-February) than summer (June-August) months.

"These findings suggest that reducing winter exacerbations by protective measures including vaccination may have significant clinical impact," comment Klaus Rabe (Christian Albrechts University Kiel, Germany) and colleagues in Chest.

The researchers assessed data from 7376 COPD patients who participated in the 1-year Prevention of Exacerbations with Tiotropium in COPD (POET-COPD) study.

In total, 2691 (36.5%) participants experienced at least one moderate or severe exacerbation between March 2008 and April 2010.

The researchers found that mean monthly exacerbation rates exhibited a distinct seasonal pattern, with rates highest in the winter (7.63 exacerbations per 100 patient-months) and lowest in the summer (3.53 exacerbations per 100 patient-months).

Indeed, after accounting for factors such as age, gender COPD severity, smoking status, body mass index, use of inhaled corticosteroids, and cardiovascular comorbidity, the team found that exacerbation rates were 2.16-fold higher in summer than winter, with rates being intermediate in the spring (March-May) and fall (September-November).

Among patients who experienced more than one exacerbation, median time to a second exacerbation was shorter among those who experienced their first between October and March than those who experienced their first between April and September, at 68 versus 99 days.

The team also found that the proportion of exacerbations treated with antibiotics was higher in winter than summer, at 86.8% versus 74.7%, while the proportion treated with systemic corticosteroids was lower in winter than summer, at 51.0% versus 61.4%.

All-cause mortality showed a seasonal pattern similar to that of exacerbations. Of the 142 deaths that occurred during the planned treatment period of 360 days, 34.5% occurred during winter and 13.4% during summer, equating to 2.28 deaths per 1000 patient-months in winter and 0.88 per 1000 patient-months in summer.

The researchers also note that although the study period coincided with the 2009 influenza A (H1N1) pandemic, it did not have a significant effect on exacerbation or death rates.

Rabe et al conclude: "Our analysis of the POET-COPD trial suggests a distinct and independent influence of season on exacerbation outcomes and mortality, resulting in a winter increase or summer decrease, respectively.

"However, further work is required to investigate the conditions by which exacerbations occur and will also help design future clinical trials more effectively and efficiently."

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