A cross-sectional study using nationally representative datasets from six middle-income countries (China, Ghana, India, Russian Federation, South Africa, and Mexico) shows that older adults with a self-reported sleep duration of six to nine hours per night exhibited significantly higher cognitive scores than individuals with a short nightly sleep duration of less than six hours or a long sleep duration of more than nine hours per night. Self-reported sleep quality also was positively correlated with a composite score of performance on five cognitive tests. Study results are published in the June issue of the Journal of Clinical Sleep Medicine.
