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

Abstract

Background: In 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 design: Prospective cross-sectional study. Methods: Metabolic-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). Results: The 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. Conclusion: This reliable 6MWD norm is helpful for the care of North-African patients aged 16–40 years.

Keywords

• 6-Min walk-distance
• Norms
• Algeria
• Lean-mass
• Physical activity