Prediction of cardiorespiratory fitness in older men infected with the human immunodeficiency virus: clinical factors and value of the six-minute walk distance.

OBJECTIVES: To investigate factors related to cardiorespiratory fitness in older human immunodeficiency virus (HIV)-infected patients and to explore the utility of 6-minute walk distance (6-MWD) in measuring fitness.
DESIGN: Cross-sectional study in clinic-based cohort.
SETTING: Veterans Affairs Medical Center, Baltimore, Maryland. PARTICIPANTS: Forty-three HIV-infected men, median age 57 (range 50-82), without recent acquired immunodeficiency syndrome-related illness and receiving antiretroviral (ARV) therapy. MEASUREMENTS: Peak oxygen utilization (VO(2)peak) according to treadmill graded exercise testing, 6-MWD, grip strength, quadriceps maximum voluntary isometric contraction, cross-sectional area, muscle quality, and muscle adiposity.
RESULTS: There was a moderate correlation between VO(2)peak (mean +/- SD; 18.4 +/- 5.6 mL/kg per minute) and 6-MWD (514 +/- 91 m) (r=0.60, P<.001). VO(2)peak was lower in subjects with hypertension (16%, P<.01) and moderate anemia (hemoglobin 10-13 gm/dL; 15%, P=.09) than in subjects without these conditions. CD4 cell count (median 356 cells/mL, range 20-1,401) and HIV-1 viral load (84% nondetectable) were not related to VO(2)peak. Among muscle parameters, only grip strength was an independent predictor of VO(2)peak. Estimation of VO(2)peak using linear regression, including age, 6-MWD, grip strength, and hypertension as independent variables, explained 61% of the variance in VO(2)peak.
CONCLUSION: Non-AIDS-related comorbidity predicts cardiorespiratory fitness in older HIV-infected men receiving ARV therapy. The 6-MWD is a valuable measure of fitness in this patient population, but a larger study with diverse subjects is needed.