BACKGROUND : Norm-referenced equations to predict the 6-minute walk distance (6MWD) in healthy Japanese subjects have not been established. The current study aimed to determine the reference values for 6MWD in healthy Japanese adults.
METHODS : Ninety-seven healthy Japanese men and women aged 40-79 years were recruited from Kyoto city using posters and flyers. Measurements of 6MWD were performed twice on an indoor 30 m track with 20 minutes rest between the two tests. Before performing the tests, age, gender, height, body weight, waist circumference, a questionnaire for health status, spirometry, and a 12-lead electrocardiogram were recorded. The 6MWD was measured following guidelines published in 2002 by the American Thoracic Society.
RESULTS : The mean age of the study subjects was 57.0±9.4, and 63 of the 97 subjects were female. The mean 6MWD for all subjects was 672±83 m, with a range of 483-903 m. The 6MWD is significantly correlated with age, height, waist circumference, forced vital capacity (FVC), and forced expiratory volume in one second (FEV₁). A multiple linear model showed age, waist circumference, and FVC were significantly associated with 6MWD and the model explained 35% of the variability in 6MWD. When FVC was replaced by height, the regression model also explained 32% of the variation. The measured 6MWD of Japanese subjects was similar to the predicted 6MWD using the equations derived from Caucasian subjects.
CONCLUSIONS : The 6MWD was affected to a substantial degree by age, waist circumference, height, and FVC in healthy Japanese adults.