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As body mass index (BMI) rises, so too does a person's risk of developing acute respiratory distress syndrome (ARDS), according to a Harvard-based research team. Moreover, BMI is directly associated with the duration of hospitalization, although not with mortality, in patients with ARDS.

In a study of nearly 1800 critically ill patients, obesity increased the risk of ARDS by 66% relative to normal body weight, according to Dr. David C. Christiani of the Harvard School of Public Health in Boston and his colleagues.

The results, Dr. Christiani told Reuters Health, suggest that "obesity is not only associated with adverse chronic health effects, but also acute respiratory failure in certain settings."

To assess the relationship between BMI and ARDS, he and his colleagues used data from the Molecular Epidemiology of ARDS study on 1795 patients at risk.

The patients were screened daily for ARDS based on standard criteria from the American European Consensus Committee, and those who developed ARDS were followed for 60-day mortality, ICU and hospital length of stay, daily organ dysfunction score, and ventilator-free days, according to the report in the January issue of Thorax.

Based on standard BMI cutoffs, 83 patients (5%) were underweight, 627 (35%) were normal weight, 605 (34%) were overweight, 364 (20%) were obese, and 116 (6%) were severely obese.

ARDS was diagnosed in 547 patients (30%).

Multivariate analysis showed an association between BMI and ARDS (adjusted odds ratio, 1.24 per SD increase). Compared to normal weight patients, adjusted odds ratios for ARDS were 1.66 for patients with BMI in the obese range, and 1.78 for patients with severe obesity.

In a subset of 1045 intubated patients without ARDS on admission, those who were obese had higher peak inspiratory pressures (p < 0.0001) and positive end expiratory pressures (p < 0.0001). Elevations in these parameters were linked to development of ARDS.

The 60-day ARDS mortality rate was 37%. In patients with ARDS, increasing BMI was linked to increased length of stay (p = 0.007) but not to mortality.

"We are looking into the mechanism of this association," Dr. Christiani said. "Fat tissue is not passive, but an active endocrine organ, secreting hormones that alter disease risk. We are measuring some of these in cases and controls."

Source: Reuters Health