Geoclimatology and sleep in Africa: A mini-review

Sleeping habits and morningness-eveningness questionnaires (chronotype), and polysomnography (internal sleep organization) were proposed to healthy volunteers living under natural climates from different locations in West Africa (Niger, Côte d'Ivoire) and Central Africa (Angola, Congo). Under the Sahelian dry climate, 138 Niger medical students (130 had afternoon naps) completed 1792 sleep questionnaires during 7-day sessions in the cool-dry and hot-dry seasons. As everywhere else on Earth, daily sleep lasted 7 to 8hours. In Abidjan (hot-humid climate), 78 medical students reported shorter sleep time, because of course schedules. Also in Abidjan, 23 African sportsmen and Expatriate soldiers slept at night and in afternoon naps. They reported similar sleep amounts than Niger students. In Congo villages, during a 5-year human African trypanosomiasis (HAT) research campaign, 45 healthy volunteers expressed morning chronotypes. The 71 HAT patients shifted from the indifferent chronotype towards morningness type. Chronotyping such patients may help evaluating treatment efficacy on brain function alterations. French soldiers executing missions in Africa were typed for morningness-eveningness. Regarding malaria prophylaxis and mosquito control, morning chronotype was more compliant than evening type. Polysomnography demonstrated internal sleep organization differences in different geoclimatic zones. The Sahelian climate promoted N3 slow-wave sleep in Africans and Expatriates during both the cool-dry and hot-dry seasons, with higher amounts in the hot-dry season. Increasing heat load by physical exercise further augmented N3. Rapid-eye-movement R sleep was high compared with values from temperate and hot-humid climates. Supramaximal exercise triggered a surprising R stage increase in the hot-dry season. In Côte d'Ivoire, Caucasian and African volunteers fragmented their sleep, although internal sleep organization approached that of temperate climates. Sleep patterns were also similar in Angola high hills and on Congo River shores. Therefore, Africans and Caucasians living in Niger hot-dry Sahelian climate exhibited major differences with those exposed to hot-humid or temperate climates.