Obesity and mortality in persons with obstructive lung disease using data from the NHANES III.

OBJECTIVES: The objective of this study was to determine the relationship between obesity and all-cause mortality among participants with obstructive lung disease in the National Health and Nutrition Examination Survey (NHANES III).
METHODS: Public data from a retrospective cohort of the 33,994 participants in NHANES III was analyzed to determine the relationship between obesity and all-cause mortality among participants with obstructive lung disease. Results were analyzed using proportional hazard models and controlled for age, sex, race, smoking status, current oral corticosteroid use, and severity of airway obstruction. Secondary analysis considered time until death from respiratory disease or time until death from chronic lower respiratory disease (excluding asthma).
RESULTS: The subset used in the analysis consisted of 2439 persons with 844 documented deaths. Extreme obesity (body mass index [BMI] >40) was significantly associated with increased respiratory disease mortality (hazard ratio [HR] 5.78; 95% confidence interval {CI} [1.09 to 30.61]) and chronic lower respiratory disease mortality (HR 13.69; 95% CI [1.45 to 129.29]). In addition, underweight status (BMI <18.5) was significantly associated with increased all-cause mortality (HR 2.42; 95% CI [1.31 to 4.46]), respiratory disease mortality (HR 7.10; 95% CI [1.94 to 26.00]) and chronic lower respiratory disease mortality (HR 14.80; 95% CI [2.24 to 97.99]).
CONCLUSION: Underweight adults had increased risk of death from all causes and respiratory conditions, compared to class I obese adults. Extreme obesity was associated with increased risk of death from respiratory conditions, but not all-cause mortality. Additional research is needed to explain the complex relationship between BMI and specific causes of mortality in the context of pulmonary disease.