Chest
Volume 141, Issue 1, January 2012, Pages 94-100
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Original Research
COPD
Influence of Season on Exacerbation Characteristics in Patients With COPD

https://doi.org/10.1378/chest.11-0281Get rights and content

Background

Patients with COPD experience more frequent exacerbations in the winter. However, little is known about the impact of the seasons on exacerbation characteristics.

Methods

Between November 1, 1995, and November 1, 2009, 307 patients in the London COPD cohort (196 men; age, mean, 68.1 years [SD, 8.4]; FEV1, mean, 1.12 L [SD, 0.46]; FEV1, mean, % predicted, 44.4% [SD, 16.1]) recorded their increase in daily symptoms and time outdoors for a median of 1,021 days (interquartile range [IQR], 631-1,576). Exacerbation was identified as ≥ 2 consecutive days with an increase in two different symptoms.

Results

There were 1,052 exacerbations in the cold seasons (November to February), of which 42.5% and 50.6% were patients who had coryzal and cough symptoms, respectively, compared with 676 exacerbations in the warm seasons (May to August), of which 31.4% and 45.4% were in patients who had coryzal and cough symptoms, respectively (P < .05). The exacerbation recovery period was longer in the cold seasons (10 days; IQR, 6-19) compared with the warm seasons (9 days; IQR, 5-16; P < .005). The decrease in outdoor activity during exacerbation, relative to a pre-exacerbation period (−14 to −8 days), was greater in the cold seasons (−0.50 h/d; IQR, −1.1 to 0) than in the warm seasons (−0.26 h/d; IQR, −0.88 to 0.18; P = .048). In the cold seasons, 8.4% of exacerbations resulted in patients who were hospitalized, compared with 4.6% of exacerbations in the warm seasons (P = .005).

Conclusions

Exacerbations are more severe between November and February. This contributes to the increased morbidity during the winter seasons.

Section snippets

Patients

This study involved 307 patients with COPD enrolled in the London COPD cohort and included their contributing data from at least 1 year between November 1, 1995, and November 1, 2009. The patients and exacerbations have been the subject of previous publications, but the current analysis and its interpretation are, to our knowledge, completely novel. COPD was defined as an FEV1 < 80%, predicted from age, height, and sex, and FEV1/FVC < 70%. Patients with significant respiratory disease other

Results

Table 1 shows the patient characteristics of the 307 patients with COPD. There were 100 (32.9%) active smokers at recruitment; 303 had a history of smoking, with a mean consumption of 50.5 pack years (SD, 35.9). Also, 262 patients (86.5%) were taking a median dose of 1,000 μg of beclomethasone equivalents (IQR, 500-1,000) of inhaled steroids; 41 patients (13.3%) were not taking inhaled steroids, and the dosage was unknown for four patients. The patients recorded diary card data for 1,037

Discussion

This study has shown that COPD exacerbations in colder periods of the year take longer to recover from and are more likely to involve cough or coryzal symptoms. We have also shown that exacerbations in the cold seasons have a greater impact on daily activity, with patients spending more time indoors and being more likely to be hospitalized. A possible explanation for our findings could be that a greater proportion of exacerbations that require treatment in cold conditions are associated with

Acknowledgments

Author contributions: Dr Donaldson: had the original idea for the study, did the statistical analysis, was involved in drafting and editing the manuscript prior to submission, and has seen and approved the final version of the manuscript.

Dr Goldring: had the original idea for the study, was involved in drafting and editing the manuscript prior to submission, and has seen and approved the final version of the manuscript.

Dr Wedzicha: had the original idea for the study, was involved in drafting

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    Funding/Support: The London COPD cohort is funded by the Medical Research Council, United Kingdom [Grant MRC G0800570].

    Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (http://www.chestpubs.org/site/misc/reprints.xhtml).

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