Background: COPD is a major contributor to the global burden of disease. Our objective was to examine changes in the mortality rate among persons with COPD in the United States.
Methods: We conducted prospective studies using data from 5,185 participants in the National Health and Nutrition Examination Survey (NHANES) I Epidemiologic Follow-up Study (baseline examination from 1971-1975; follow-up from 1992-1993) and 10,954 participants of the NHANES III Linked Mortality Study (baseline examination from 1988-1994; follow-up through 2006).
Results: The age-adjusted rate (per 1,000 person-years) among participants with moderate or severe COPD (23.9 and 20.2) was about 2.5 to 3 times higher than the rate among participants with normal lung function (10.4 and 6.2) in NHANES I and NHANES III, respectively. Compared with NHANES I, the mortality rate among participants in NHANES III decreased by 15.8% for those with moderate or severe COPD, 25.2% for those with mild COPD, 35.9% for those with respiratory symptoms with normal lung function, 16.6% for those with restrictive impairment, and 40.1% for those with normal lung function. However, the decrease did not reach statistical significance among participants with moderate or severe COPD. The decreases in the mortality rate among men with moderate or severe COPD (-17.8%) or with restrictive impairment (-35.1%) exceeded the changes among women (+3% and -6.1%, respectively).
Conclusions: The secular decline in the mortality rate in the United States benefited people with COPD less than those with normal lung function.