BMI, Changes in Weight Linked to Mortality in Fibrotic Interstitial Lung Disease

After careful consideration, the American Thoracic Society canceled its annual meeting that was to take place in Philadelphia, Pennsylvania from May 15-20, because of the ongoing coronavirus disease 2019 (COVID-19) pandemic. Although the live events will not proceed as planned, our readers can still find coverage of research that was scheduled to be presented at the meeting. A virtual event is being planned for later this year.

Both body mass index (BMI) and change in weight have been linked to 1-year mortality risk in patients with fibrotic interstitial lung disease (ILD), according to findings intended to be presented at the American Thoracic Society (ATS) International Conference, but that may be provided in a virtual format later this year.

 Recognizing the challenging aspect of mortality risk assessment in the population of individuals with ILD, investigators conducted the 6-center Canadian Registry for Pulmonary Fibrosis (CARE-PF) with a total of 1787 patients with fibrotic ILD. The investigators sought to determine the prognostic significance of BMI and change in weight among major ILD subtypes, adjusting for an established mortality prediction model. All participants had their weight and height calculated at the time of each pulmonary function test, with these measurements used to calculate BMI.

The participants were categorized as being underweight (BMI <18.5 kg/m²), normal weight (BMI 18.5-24.9 kg/m²), overweight (BMI 25-29.9 kg/m²), or obese (BMI >30 kg/m²). All of the patients’ annual changes in weight were obtained for all the years of study follow-up. Cox regression models with time-varying covariates were used to assess the relationship between BMI and change in weight with subsequent 1-year mortality or transplant.

Of the 1787 patients who participated in the study, the most common diagnosis was connective tissue disease-associated ILD, which was reported in 46% of individuals, followed by idiopathic pulmonary fibrosis (IPF) in 28% of individuals, unclassifiable ILD in 18% of individuals, and hypersensitivity pneumonitis in 8% of individuals. Based on an adjusted analysis, a significant association between BMI and 1-year mortality was demonstrated (hazard ratio [HR], 0.95; 95% CI, 0.93-0.98; P <.001). Mortality rates were highest in participants who were underweight and lowest in those who were overweight or obese, according to BMI.

Based on adjusted analysis, annual change in weight was significantly associated with mortality (HR, 0.96; 95% CI, 0.93-0.99; P =.03).  Furthermore, participants with a body weight loss of >2 kg within 1 year had a slightly increased risk for death within 1 year, with a plateau in risk shown in those individuals with a greater loss of weight. The results were similar when adjusting the analysis for an IPF vs non-IPF diagnosis and when patients who were undergoing lung transplant were censored. The investigators concluded that both weight loss and BMI may be clinically useful prognostic variables in patients with fibrotic ILD.

Reference

Comes A, Wong AW, Fisher JH, et al. Association of body mass index and change in weight with mortality in patients with fibrotic interstitial lung disease. Am J Respir Crit Care Med. 2020;201:A1096.

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