Self-estimates of sleep in african students in a dry tropical climate

Sleep behavior was examined in African medical students living in Niamey, Niger (latitude 13° 30' North), a sub-Saharan country in Western Africa. A 12-item questionnaire was used to obtain subjective estimates of sleep duration, structure and quality, and self-rating of the restorative quality of sleep (morale, mood, fatigue, working ability). The experiment was divided into two 7-day periods, January (‘cool-dry’ season, 88 subjects), and May (‘hot-dry’ season, 53 subjects). The questionnaire was completed after night sleep and/or naps. All subjects lived in student quarters, sleeping on their beds, with sheets and/or blankets. They slept an average of 7·5 h a day, most of them having afternoon naps. They experienced no major seasonal variation in their sleep behavior, but for an increased number of awakenings during the hot season. Restorative quality of sleep scored lower after a nap than after nocturnal sleep. Therefore, general sleep characteristics were not modified by seasonal temperature variations in African native students, perhaps because of the limited changes in daylight at the low latitude of Niamey.