Reference Equations for the 6-Minute Walk Test Distance in Outpatient Obese Patients Aged 17 to 45 Years

Abstract

Background The 6-minute walk test (6MWT) is extensively used to assess the exercise capacity of obese populations and offers a reference for devising intervention measures. While reference equations for the 6MWT distance for various populations have been proposed internationally, there is a scarcity of studies on reference equations for the 6MWT distance among Chinese obese subjects aged 17 to 45 years with a BMI ≥ 30 kg/m2. Objective To develop reference equations for the 6MWT distance for outpatient obese subjects aged 17 to 45 years and to assess its influencing factors. Methods Following the American Thoracic Society guidelines, from June 2022 to September 2023, 143 adults aged 17 to 45 years with a BMI ≥30 kg/m2 (71 males and 72 females) who visitied the Department of Endocrinology, Northern Jiangsu People's Hospital, were prospectively selected for anthropometric measurements and the 6MWT. A stepwise multiple regression model was employed to establish reference equations for the 6MWT distance, and the newly developed equations were compared with existing prediction equations. Results The average 6MWT distance for the 143 subjects was (506.1±49.8) m, with males averaging (515.7±50.14) m, which was greater than the females' average of (496.6±47.9) m (P<0.05). Across age groups 17-23, 24-30, 31-37, and 38-45 years, differences in 6MWT distances between males and females were statistically significant (P<0.05). In males, weight, BMI, HRmax, resting heart rate difference (ΔHR), waist circumference, diastolic blood pressure difference (ΔDBP), and Borg scale score difference (ΔBorg) were related to 6MWT distance (P<0.05), whereas in females, weight, BMI, and waist circumference were related to 6MWT distance (P<0.05). Incorporating potential influencing factors into a stepwise multiple linear regression equation, the final reference formulas were established as follows: for males, y=494.463+1.414×ΔHR-3.903×BMI+0.874×HRmax, R2=0.429; for females, y=670.448+0.299×ΔHR-4.342×BMI-0.195×HRmax, R2=0.312. Conclusion In outpatient obese patients aged 17 to 45 years, males had a longer average 6MWT distance than females, with significant differences across different age groups. Factors such as weight, BMI, HRmax, ΔHR, wait cirumference ΔDBP, and ΔBorg were associated with 6MWT distance in males, while weight, BMI, waist cirumference and ΔSBP were related to 6MWT distance in females. Through multiple linear regression analysis, reference equations predicting 6MWT distance were established for males and females, providing valuable references for assessing individual physical fitness levels.

Keywords

• obesity|walk test|distance equation|17~45 years old|6-minute walk test|root cause analysis