Reference Equation for the Six-Minute Walk Test in Brazilian Patients with Obesity

Abstract

Abstract Background: Obesity has repercussions on functional capacity (FC). The six-minute walk test (6MWT) is a useful tool for assessing submaximal FC, and the distance reached at 6 minutes of walking (D6MW) is a relevant prognostic marker. Objective: This paper aims to establish a reference equation for the distance predicted in 6MWT in obese Brazilian subjects. Methods: This study included 460 patients (306 women), with a body mass index (BMI) > 30 kg/m2, 71% (328) of whom presented a grade III obesity (BMI ≥ 40 Kg/m²) and were evaluated with 6MWT. Heart rate, blood pressure, oxygen saturation and Borg scale perception of effort were recorded before and after the 6MWT. For statistical analysis, Kolmogorov-Smirnov tests, an unpaired T-Test, Pearson's correlation, and multiple linear regression were used, together with a significance level set at p<0.05. Results: Gender, age, and BMI were significantly correlated with D6MW and were identified by multiple linear regression as the best predictors of the D6MW. Together, they explain 48.7% of the D6MW variance for obese Brazilian subjects. Based on these findings, an equation was proposed - D6MW = 930.138 + (27.130 x Genderfemales = 0; males = 1) − (5.550 x BMI kg/m2) − (4.442 x Age years). When the average of the D6MW obtained with the above equation was compared to the average calculated with the equations described in medical literature for healthy and obese individuals, the latter tended to overestimate the D6MW. Conclusion: The proposed reference equation exhibited better assessment of FC in obese Brazilian patients, providing proper subsidies for the follow up ofinterventions in this population..