Major role for body weight in COPD, asthma risk

Sep 24 2013

Results from a large study in Italy show that increasing body weight is associated with chronic obstructive pulmonary disease (COPD) and asthma risk, independent of smoking history.

The research team, led by Mario Cazzola (University of Rome Tor Vergata, Italy), analyzed general practice data from 424,889 patients, including 30,089 with asthma and 29,360 with COPD.

A diagnosis of asthma was significantly associated with body mass index (BMI) across all smoking statuses, including those who had never smoked. For example, the prevalence of asthma in normal weight never smokers was 7.17% compared with 9.83% in obese never smokers.

And, with the exception of former smokers, being underweight had an apparent protective effect against asthma; for example, the prevalence of asthma in obese current smokers was 8.67% but only 6.48% in those who were underweight.

Meanwhile, having an abnormal BMI – being underweight, overweight or obese – was associated with an increased odds for COPD, regardless of smoking habit, apart from in underweight never smokers.

And, although approximately 30% of all patients with COPD had never smoked, smoking status was significantly associated with the disease, being diagnosed in 11.94% and 12.64% of current and former smokers, respectively, compared with 3.99% of never smokers.

By contrast, asthma prevalence was comparable across smoking statuses at 7.53%, 6.85%, and 7.92%, respectively, suggesting that the habit has no impact on asthma risk.

“Our results demonstrate that an increase in BMI is frequently associated with the diagnosis of COPD and asthma, suggesting that the probability of suffering from these diseases increases with the increase in body weight regardless of the smoking status,” Cazzola and team write in Respiratory Medicine.

They also note that this association was strongest in women, while being underweight was most significantly associated with COPD in men.

The authors say that, although the mechanism underlying these associations is unclear and given the key role of BMI in COPD and asthma, it is important to “look beyond smoking and also, probably, atopy when we manage patients suffering from these diseases.”

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