1. Faculty of Medicine and Health Sciences, Physiotherapy Division, Department of Health and Rehabilitation Sciences, Stellenbosch University, Cape Town 8000, South Africa
2. Research Unit iDN—Interdisciplinary Developmental Neuroscience, Division of Phoniatrics, Medical University of Graz, 8010 Graz, Austria
3. Biostatistics Unit, South African Medical Research Council, Cape Town 7500, South Africa
4. Statistics and Population Studies, University of the Western Cape, Cape Town 8000, South Africa
5. Faculty of Medicine and Health Sciences, Department of Psychiatry, Stellenbosch University, Cape Town 8000, South Africa