Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Doctor of Philosophy

Program

Health and Rehabilitation Sciences

Supervisor

Gilliland, Jason

2nd Supervisor

Madill, Janet

Affiliation

Brescia University College at the University of Western Ontario

Co-Supervisor

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.

Summary for Lay Audience

Interstitial lung disease (ILD) and its treatments put patients at risk of poor nutrition. However, little is known about the link between nutrition and ILD, nor about the influence of nutrition on survival in patients with ILD. Most ILD nutrition research has focused on weight and body mass index (BMI). Therefore, the primary objective of this study was to determine how common malnutrition is in ILD patients using the subjective global assessment (SGA), and to estimate body composition (lean body mass and body fat) using bioelectrical impedance analysis (BIA) among 78 individuals diagnosed with ILD. A second objective of this research was to investigate if suspected markers of nutrition status, such as, standardized phase angle (SPhA) and impedance ratio z-score (z-IR) measured using BIA, can be used to accurately identify malnutrition. The third objective of this research was to explore how nutrition status and body composition are related to exercise capacity, using 6-minute walk distance (6MWD). Lastly, the fourth objective explored the relationship between body composition and nutrition status with survival. A large portion of the patients were mildly malnourished (49%). Lean body mass controlled for age, sex and height, and nutrition status were significantly associated with exercise capacity regardless of the severity of ILD. Low BMI, low muscle mass and low body fat were associated with severe malnutrition. z-IR, but not SPhA, was associated with severe malnutrition. Age, BMI, lean body mass, body fat, exercise capacity, disease severity and severe malnutrition predicted survival in ILD patients. Muscle mass controlled for age, sex and height, and severe malnutrition predicted survival regardless of disease severity. These results justify future exploration into the nutritional status of ILD patients which can be used to develop individualized nutrition care plan for patients with ILD. Future research should assess if nutrition interventions can increase muscle mass and/or exercise capacity. When possible, muscle mass should be measured along with or in place of BMI as it can better identify those at risk of death with ILD.

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