6-Min walk-test data in healthy North-African subjects aged 16–40 years

BackgroundIn North-African and Mediterranean countries (such as Algeria, Tunisia, Morocco, Libya) no local 6-Min walk-distance (6MWD) norms exist for subjects aged 16–40 years.Aims(i) To test the applicability and reliability of the previously published norms for Arab or Mediterranean subjects aged ⩾ 16 years in this population and, if required, (ii) to establish a 6MWD reference equation for use in North-African subjects aged 16–40 years and prospectively assess its reliability and to propose a clear scheme to interpret the measured 6MWD.Study designProspective cross-sectional study.MethodsMetabolic-equivalent-task (MET) walking, moderate, and vigorous activities, anthropometric, spirometric and 6-Min walk-test (6MWD, heart-rate, oxy-haemoglobin-saturation) data were measured/noted in 200 healthy Algerian subjects aged 16–40 years (100 women). Univariate and multiple linear regression analyses were used to find-out 6MWD influencing factors, reference equation and to determine the lower-limit-of-normal (LLN).ResultsThe mean ± SD of 200 included subjects’ age, height, weight, body-mass-index (BMI), lean-mass, first-second-forced-expiratory-volume (FEV1) and MET moderate activity were, respectively, 27.5 ± 6.7 years, 169 ± 9 cm, 69.3 ± 11.5 kg, 24.1 ± 3.6 kg/m2, 16.7 ± 7.4 kg, 3.70 ± 0.74 L and 370 ± 686 min/week. Their 6MWD mean ± SD (minimum–maximum) was 680 ± 70 (540–888) m. The published norms for Italian and Saudi-Arabian populations did not reliably predict measured 6MWD. The following 6MWD influencing factors were noted: FEV1, BMI, sex, lean-mass, MET moderate activity and age (p < 0.001). A reference equation, explaining 58.7% of the 6MWD variability, was established: 6MWD (m) = 800.05 + 64.71 × Sex (men:1/women:0) − 10.23 × BMI (kg/m2) − 1.63 × Age (years) + 2.05 × Weight (kg). To calculate the 6MWD LLN subtract 74.31 m from the predicted value. In a second group of 39 young subjects (19 women) prospectively studied to validate the reference equation, the agreement between the measured and predicted 6MWDs was adequate.ConclusionThis reliable 6MWD norm is helpful for the care of North-African patients aged 16–40 years.