Background: Previous studies have documented the prognostic value of low body weight in patients with COPD and also in general populations. However, it is not clear whether low body weight is a risk factor for COPD or a consequence of established disease.
Study objective: To determine whether asymptomatic subjects with low initial body mass were at a greater risk of having COPD develop during subsequent follow-up.
Design and subjects: Observational retrospective study of 458 male and 192 female participants (age range, 40 to 73 years) in the Baltimore Longitudinal Study of Aging. At baseline, the participants did not have COPD. After mean follow-up periods of 10.2 years for the men and 6.4 years for the women, 40 men and 7 women received a diagnosis of COPD.
Methods: Cox proportional-hazards regression models were used to assess the relationship between COPD diagnosis and baseline body mass index (BMI) in men.
Results: The risk of COPD developing in men varied inversely with baseline BMI, even after adjusting for other risk factors, including cigarette smoking, age, FEV(1) percent predicted, abdominal obesity, and educational status. In men, the relative risk of COPD developing for the lowest BMI tertile relative to the highest tertile was 2.76 (95% confidence interval, 1.15 to 6.59). The small number of women who had COPD did not allow us to draw conclusions regarding BMI as a risk factor for COPD.
Conclusion: After controlling for confounding variables, men with low BMI are at increased risk for getting COPD.