Exercise intolerance is an important symptom in patients with chronic obstructive pulmonary disease (COPD). Reduced lung function and skeletal muscle weakness are potential causes of exercise intolerance. Inflammatory mechanisms are associated with lung disease, but their relationship with exercise intolerance and muscle weakness is not well understood. The study aim was to determine predictors of exercise tolerance in older persons with ATS defined airways obstruction.
Cross sectional analysis of a subset of 3075 participants aged 70–79 enrolled in the Health Aging and Body Composition (Health ABC) study. We selected 183 participants with ATS defined airways obstruction and complete physical function measures. Knee extensor strength was measured using isokinetic dynamometry and hand grip strength (GRIP) was measured isometrically. Muscle mass was estimated using thigh cross sectional area by CT scan. Serum Interleukin-6 (IL-6), C Reactive Protein (CRP), and Tumor Necrosis Factor-alpha (TNF) were measured. Pearson correlation coefficients were estimated to determine relationship between inflammatory mediators and measures of muscle strength.Exercise tolerance was defined as the time to walk 400 meters at a fast, but sustainable pace. This outcome variable was dichotomized into time > 6 minutes and time ≤ 6minutes.
There were no significant correlations between KMAX, GRIP, and maximum inspiratory pressure (MIP) with inflammatory mediators (IL-6, TNF, and CRP). Univariate predictors of time to complete the 400 meter walk test were age, race, history of smoking, percent predicted FEV1 [FEV1(%)], GRIP, KMAX, MIP, and IL-6 levels. KMAX, IL-6 levels, and MIP remained significant on multivariable analysis (table 1
Predictors of exercise intolerance (Multivariable analysis)VariableOdds Ratio95% CIP valueKnee extensor strength (Nm)0.470.3–0.80.003Maximal inspiratory pressure (MIP)0.520.3–0.80.003IL-61.621.09–2.40.018). Although FEV1(%) correlated with IL-6, it was not an independent predictor of exercise intolerance.CONCLUSIONS: KMAX, MIP, and IL-6 are important indicators of exercise performance in elderly patients with airway obstruction.
MIP is a better predictor than FEV1(%) for exercise intolerance in patients with obstructive airway disease. Suppression of systemic IL-6 may be a potential mechanism to improve exercise capacity in COPD patients.
S. Yende, None.