Body mass index, asthma, and respiratory symptoms: a population-based study

Objective: To estimate the prevalence of respiratory symptoms and asthma, according to body mass index (BMI), as well as to evaluate factors associated with physiciandiagnosed asthma, in individuals >= 40 years of age. Methods: This was a population-based cross-sectional study conducted in Florianopolis, Brazil, with probability sampling. Data were collected during home visits. Demographic data were collected, as were reports of physician-diagnosed asthma, respiratory symptoms, medications in use, and comorbidities. Anthropometric measurements were taken. Individuals also underwent spirometry before and after bronchodilator administration. Individuals were categorized as being of normal weight (BMI < 25 kg/m(2)), overweight (25 kg/m(2) >= BMI < 30 kg/m(2)), or obese (BMI >= 30 kg/m(2)). Results: A total of 1,026 individuals were evaluated, 274 (26.7%) were of normal weight, 436 (42.5%) were overweight, and 316 (30.8%) were obese. The prevalence of physician-diagnosed asthma was 11.0%. The prevalence of obesity was higher in women (p = 0.03), as it was in respondents with <= 4 years of schooling (p < 0.001) or a family income of 3-10 times the national minimum wage. Physician-diagnosed asthma was more common among obese individuals than among those who were overweight and those of normal weight (16.1%, 9.9%, and 8.0%, respectively; p = 0.04), as were dyspnea (35.5%, 22.5%, and 17.9%, respectively; p < 0.001) and wheezing in the last year (25.6%, 11.9%, and 14.6%, respectively; p < 0.001). These results were independent of patient smoking status. In addition, obese individuals were three times more likely to report physician-diagnosed asthma than were those of normal weight (p = 0.005). Conclusions: A report of physician-diagnosed asthma showed a significant association with being >= 40 years of age and with having a BMI >= 30 kg/m(2). Being obese tripled the chance of physician-diagnosed asthma.