Obesity and its correlation with spirometric variables in patients with asthma.

Background: The severity of bronchial asthma has been associated with increased body mass index (BMI) in several studies. We studied obesity in the asthmatic population and its possible correlation with spirometric variables.

Methods: We reviewed the medical records of 200 patients who underwent spirometry and were followed up in a pulmonary clinic for asthma. Ninety patients fulfilled the inclusion criteria. Patients were divided into Group? (forced expiratory volume in 1 second [FEV1] = 80%, n = 64) and Group II (FEV1 60% to 79%, n = 26). Patients with BMI = 30 were labeled as obese. In each group, correlates of BMI and forced expiratory flow, midexpiratory phase (FEF25%-75%) were analyzed with linear regression.

Results: The mean ages were 33.9 -/+ 13 years and 33.73 -/+ 10 years in Groups I and II, respectively. The mean BMI was 30.2 +/ 6 (Group I) and 30.36 -/+ 6 (Group II). BMI = 30 was seen in 56.7% of patients in Group I and 53.3% in Group II. BMI did not correlate with spirometric variables in both groups. FEF25%-75% correlated with FEV1 and FEV1:forced vital capacity (FVC) in Group I (P = .003 and .0001, respectively) and FEV1:FVC in Group II (P = .0001). In Group 1, 38% of the patients had FEF25%-75% less than 80%.

Conclusions: Although obesity was prevalent in asthmatic patients, BMI did not correlate with any of the spirometric variables. A significant number of patients with normal FEV1 had impaired midflow rates that may reflect ongoing small airway inflammation.