Influence of nutrition status and body composition on exercise capacity and survival among individuals with interstitial lung disease: a cross-sectional study in an outpatient setting.
Abstract
Interstitial lung disease (ILD) and its associated treatments have the potential to put patients at nutrition risk. However, minimal is known about the relationship between nutritional status on disease severity and prognosis in ILD. Existing research is limited by its focus on weight and body mass index (BMI). Therefore, the primary objective of this cross-sectional, prospective study was to determine the prevalence of malnutrition using the subjective global assessment (SGA) and to estimate body composition using bioelectrical impedance analysis (BIA) among individuals with ILD (n = 78). A second objective of this research was to investigate the appropriateness of bioimpedance parameters such as standardized phase angle (SPhA) and impedance ratio z-score (z-IR) as surrogate markers of malnutrition. The third objective of this research was to evaluate how nutrition status and body composition are related to functional exercise capacity using 6-minute walk distance (6MWD). The fourth objective explored the relationship between fat-free mass index z-score (z-FFMI) and body fat mass index z-score (z-BFMI), body composition measures which are controlled for age and sex, and nutrition status, with survival. Results indicate that most participants were mildly malnourished (49%). Additionally, 11.5% of patients had normal body composition, 20.5% were classified as sarcopenic, 60% were obese and the remaining 8% were classified as sarcopenic obese. z-FFMI and SGA were significantly associated with exercise capacity independent of lung function. Low BMI, z-FFMI and z-BFMI were associated with severe malnutrition. SPhA did not correlate with nutrition status, however, increased z-IR significantly increased the odds of severe malnutrition. Age, BMI, z-FFMI, z-BFMI, exercise capacity, disease severity, and severe malnutrition were significant predictors of survival. z-FFMI and severe malnutrition were significantly associated with survival independent of disease severity. These results are sufficiently encouraging to warrant further research into the nutritional status of ILD patients. Future research should assess if nutrition interventions can improve fat-free mass and functional exercise capacity in patients with ILD. Assessment of fat-free mass should be considered alongside or in place of BMI as a nutritional variable when analyzing survival risk in ILD patients as it can better identify those as risk of death.