Obstructive lung disease and low lung function in adults in the United States - Data from the National Health and Nutrition Examination Survey, 1988-1994

Background: Obstructive lung disease (OLD) is an important cause of morbidi ty and mortality in the US adult population. Potentially treatable mild cas es of OLD often go undetected. This analysis determines the national estima tes of reported OLD and low lung function in the US adult population. Methods: We examined data from the Third National Health and Nutrition Exam ination Survey (NHANES III), a multistage probability representative sample of the US population. A total of 20050 US adults participated in NHANES II I from 1988 to 1994. Our main outcome mea; sures were low lung function (a condition determined to be present if the forced expiratory volume in 1 sec ond-forced vital capacity ratio was less than 0.7 and the forced expiratory volume in 1 second was less than 80% of the predicted value), a physician diagnosis of OLD (chronic bronchitis, asthma, or emphysema), and respirator y symptoms. Results: Overall a mean (SE) of 6.8% (0.3%) of the population had low lung function, and 8.5% (0.3%) of the population reported OLD. Obstructive lung disease (age-adjusted to study population) was currently reported among 12. 5% (0.7%) of current smokers, 9.4% (0.6%) of former smokers, 3.1% (1.1%) of pipe or cigar smokers, and 5.8% (0.4%) of never smokers. Surprisingly, 63. 3% (0.2%) of the subjects with documented low lung function had no prior or current reported diagnosis of any OLD. Conclusions: This study demonstrates that OLD is present in a substantive n umber of US adults. In addition, many US adults have low lung function but no reported OLD diagnosis, which may indicate the presence of undiagnosed l ung disease.