Document Detail

Inhaled steroids and mortality in COPD: bias from unaccounted immortal time.
MedLine Citation:
PMID:  15065827     Owner:  NLM     Status:  MEDLINE    
A recent observational study, which suggested that inhaled corticosteroids (ICS) with or without long-acting bronchodilators are effective at reducing all-cause mortality in chronic obstructive pulmonary disease (COPD) patients, may be subject to immortal time bias. This bias was assessed using a population-based cohort of 3,524 newly treated COPD patients from Saskatchewan, Canada, observed from 1990-1999. Regular users of bronchodilators or ICS were followed for 3 yrs, during which time 860 deaths occurred. Cox's proportional hazards model was used to compare the hierarchical intention-to-treat approach employed in the recent study, a technique subject to bias from two sources of immortal time, with the conventional intention-to-treat approach and the according-to-treatment approach. The adjusted rate ratio of death using the hierarchical intention-to-treat approach was 0.66 (95%) confidence interval (CI) 0.57-0.76) for ICS use relative to bronchodilator use, compared with 0.75 (95% CI 0.62-0.90) with the conventional intention-to-treat approach. Conversely, the rate ratio was 0.94 (95% CI 0.81-1.09) with the according-to-treatment approach, which accounts for both sources of immortal time. In this study, regular inhaled corticosteroid use in chronic obstructive pulmonary disease was not found to reduce all-cause mortality. Suggestion of this benefit from a previous observational study is the result of bias from unaccounted immortal time in its cohort design and analysis.
S Suissa
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The European respiratory journal     Volume:  23     ISSN:  0903-1936     ISO Abbreviation:  Eur. Respir. J.     Publication Date:  2004 Mar 
Date Detail:
Created Date:  2004-04-06     Completed Date:  2004-06-17     Revised Date:  2013-05-23    
Medline Journal Info:
Nlm Unique ID:  8803460     Medline TA:  Eur Respir J     Country:  Denmark    
Other Details:
Languages:  eng     Pagination:  391-5     Citation Subset:  IM    
Division of Clinical Epidemiology, Royal Victoria Hospital, McGill University Health Centre, Montreal, Québec, Canada.
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MeSH Terms
Administration, Inhalation
Bias (Epidemiology)
Bronchodilator Agents / administration & dosage,  therapeutic use
Cohort Studies
Databases, Factual
Glucocorticoids / administration & dosage*,  therapeutic use
Proportional Hazards Models
Pulmonary Disease, Chronic Obstructive / drug therapy*,  mortality*
Research Design
Time Factors
Reg. No./Substance:
0/Aerosols; 0/Bronchodilator Agents; 0/Glucocorticoids
Comment In:
Eur Respir J. 2004 Jul;24(1):190-1; author reply 191-2   [PMID:  15293626 ]
Eur Respir J. 2004 Oct;24(4):710-1; author reply 711   [PMID:  15459156 ]

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