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

Abstract

BACKGROUND: The 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 exercise capacity, is widely used in chronic cardiopulmonary and non-cardiopulmonary disorders. However, th absence of reference standards for Nigerian school-aged children limits its utility in this age group OBJECTIVES: To develop normative values and equations for the 6MWT of school-aged Nigerian children METHODS: In a cross-sectional study, healthy Nigerian children aged 6-11 years in Lagos 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 physiological data [pre-walk, immediate post-walk and 5th-minute post-walk heart rate (HR), oxygen saturation (SpO2), systolic blood pressure (SBP), diastolic blood pressure (DBP) and rating of perceived exertion (RPE)] and the difference between pre-walk and post-walk HR (HR change), SpO2 (SpO2 change), SBP (SBP change), DBP (DBP change) and RPE (RPE change). Primary outcomes:six-minute walk distance (6MWD) in meters. RESULTS: Overall, 627 pupils (52.1% girls) walked 504.6 (66.6) m (95% CI: 499.4, 509.8), ranging from 326.6 to 673.0 m; boys walking 16 m longer (p=0.002). Stepwise linear regression yielded 6MWD=347.9+14(Age in years)+1.6(HR change)+17.6(sex; male=1, female=0)+1.2(SBP change);R square=0.25.Previously published reference equations mostly over-estimated Nigerian children's 6MWD. CONCLUSION: The reference values and equations, after validation in other Nigerian geographic populations, may be useful for the functional evaluation of Nigerian children aged 6-11 years with chronic childhood disorders.