1. Wits Sleep Laboratory, Brain Function Research Group, School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, Gauteng, South Africa
2. Division of Exercise Science and Sports Medicine, Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
3. Feinberg School of Medicine, Northwestern University, Chicago, IL
4. Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey, United Kingdom
5. MRC/Wits Rural Public Health and Health Transitions Research Unit (Agincourt), School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa