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Obesity linked to reduced lung function in asthmatics

By Jeremy Cockerill | July 15, 2010

Source: MedWire News

Obese patients with asthma tend to have poorer lung function and more comorbidities than their normal-weight counterparts, research shows.

Previous studies have shown that overweight and obesity are associated with a significantly increased risk for asthma, and that there is a dose-response effect in the relationship, with increasing body mass index (BMI) associated with an increasing risk for the respiratory condition, explain Smita Pakhale (Ottawa Hospital, Ontario, Canada) and team.

To compare characteristics and severity of disease between obese and normal-weight people with asthma, and to investigate whether obesity increases the risk for asthma misdiagnosis, the researchers studied 496 patients, aged at least 16 years, with reported doctor-diagnosed asthma who were either obese, defined as a BMI of at least 30 kg/m2, or of normal weight, defined as a BMI of 18-25 kg/m2.

Extensive assessments confirmed asthma in 346 patients and ruled-out the condition in 150. Of the 346 patients with confirmed asthma, 165 were obese and 181 were of normal weight.

Analysis revealed that obese asthma patients (mean BMI=35.9 kg/m2) had a significantly lower mean pre- and post-bronchodilation percent of predicted FEV1 values than normal-weight patients (mean BMI=23.2 kg/m2), at 84.7% versus 88.0%, and 90.2% versus 94.3%, respectively.

Obese asthma patients were also significantly more likely to be male than normal-weight asthma patients, and to have a history of hypertension and gastroesophageal reflux disease, at adjusted odds ratios (aORs) of 2.24, 2.92, and 4.11, respectively.

The researchers also found that men, older individuals and those with a higher FEV1 were more likely to have been misdiagnosed with asthma than women, younger individuals, and those with a lower FEV1.

Obesity was not an independent risk factor for misdiagnosis, but obese individuals who had made urgent visits to a healthcare provider for respiratory symptoms in the past year were significantly more likely to be misdiagnosed than normal-weight individuals who had made urgent visits during the past year, at an aOR of 4.08.

Pakhale and team conclude in the journal Chest: “Obese people with asthma have lower lung function and more comorbidities compared with normal-weight people with asthma.”

They add: “Healthcare providers need to order appropriate objective lung function testing in order to avoid falsely labeling patients who are both obese and nonobese as having asthma.”