Development of reference equations for the six-minute walk distance of school-aged Nigerian children

Abstract

ABSTRACTBackgroundThe six-minute walk test (6MWT), a simple, reliable and valid test that uses the distance walked in six minutes (six-minute walk distance, 6MWD) to quantify functional capacity, is widely used in chronic cardiopulmonary and non-cardiopulmonary disorders. However, absence of reference standards for Nigerian school-age children limits its use in this age group.ObjectivesTo develop normative values and equations for the 6MWT of school-aged Nigerian children.MethodsIn a cross-sectional study, healthy children aged 6-11 years in Lagos, Nigeria, completed 6MWT on 20-meter straight outdoor courses in their schools following standardized guidelines. Potential predictors: demographic (age, sex), anthropometric (height, weight, chest circumference, leg length) and physiologic data [pre-walk, immediate post-walk and 5th minute-post-walk heart rate (HR), oxygen saturation (SpO2), systolic pressure (SBP), diastolic blood pressure (DBP) and rating of perceived exertion (RPE)] and difference between pre-walk and post-walk HR (ΔHR), SpO2 ((ΔSpO2), SBP (ΔSBP), DBP (ΔDBP) and RPE (ΔRPE). Primary outcome: six-minute walk distance (6MWD) in metres.ResultsOverall, 627 pupils (52.1% girls) walked 504.6 ± 66.6 m (95% CI: 499.4, 509.8), ranging from 326.6 m to 673.0 m; 16 m longer in boys (p=0.002). Stepwise linear regression yielded: 6MWD (m) = 347.9 + 14 (Age) + 1.6 (ΔHR) + 17.6 (Sex) + 1.2 (ΔSBP); R2 =0.25. Previously published reference equations over-estimated Nigerian children’s 6MWD.ConclusionThe reference values and prediction equations, after validation in other Nigerian populations, may be useful for functional evaluation of Nigerian children aged 6-11 years with chronic childhood disorders.