Body mass index and chronic airflow limitation in a worldwide population-based study

Nutritional status has been associated with clinical outcome in chronic airflow limitation (CAL), but epidemiological studies are scarce. We aimed to assess the relationship between body mass index (BMI) and CAL, taking into account confounding factors. 18,606 participants (49% male, 21% smokers, mean age: 55.8 ± 11.2 years, mean BMI: 26.7 ± 5.5 kg/m(2)) of the BOLD initiative from 26 sites in 23 countries were included. CAL was defined as post-bronchodilator forced expiratory volume in the first second/forced vital capacity < lower limit of normal. Low and obese BMI were defined as <21 kg/m(2) and ≥30 kg/m(2), respectively. Multivariate logistic regression analysis controlled for confounders age, sex and smoking, and meta-analysis of between-site heterogeneity and clustering. Prevalence of low and obese BMI, smoking history and prevalence of CAL were highly variable between sites. After adjustment for confounders, the meta-analysis of all sites showed that compared to subjects without CAL, low BMI was more frequent, (adjusted odds ratio (OR): 2.23 (95% confidence interval: 1.75, 2.85)) and conversely, obesity was less frequent in subjects with CAL (adjusted OR: 0.78 (0.65, 0.94)). In a worldwide population sample, CAL was associated with lower BMI, even after adjusting for confounding factors age, gender, smoking and between-site heterogeneity. These results indicate a CAL-specific association with body composition.