Predicting 15 year chronic bronchitis mortality in the Whitehall Study.

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Abstract
Fifteen year chronic bronchitis mortality was investigated among 17,717 male civil servants aged 40-64 years participating in the Whitehall Study. Associations were assessed between mortality and Medical Research Council standardised questions about chronic phlegm production and breathlessness, and a measure of lung function. Low FEV1 was the most powerful single predictor of mortality; controlling for age, smoking habits and employment grade, the relative hazards ratio (RHR) was 20. Using mortality rates standardised for age and smoking, the proportion of mortality in the total population statistically attributable to low FEV1 (population excess fraction) was 57%. Breathlessness while walking on the level was the best predictor among the questions and combinations of questions; the relative hazards ratio was 12 and the population excess fraction, 39%. A Medical Research Council definition of chronic bronchitis including chronic phlegm production and breathlessness was also strongly associated with chronic bronchitis mortality (RHR = 13); however, the population excess fraction was only 20%. This definition identified only 30% of the 64 deaths, and added almost nothing to prediction by FEV1 alone. The results suggest that although the combination of chronic phlegm production and chronic airflow limitation is strongly associated with mortality from chronic bronchitis, the presence of chronic phlegm production alone is not associated with mortality.