Mammalian Sleep, Longevity, and Energy Metabolism; pp. 425–446

Based on data for 53 mammalian species reported in the literature, statistical analyses revealed that daily sleep quotas correlate positively with metabolic rate and negatively with maximum life span and brain weight. Sleep cycle length correlates positively with life span and brain weight and negatively with metabolic rate. Paradoxical sleep figures in these intercorrelations only by virtue of its positive correlation with slow wave sleep. The correlation between sleep time and metabolic rate suggests that sleep has the function of enforcing rest and limiting metabolic requirements, although some inconsistent findings are noted. Strong correlations of cycle length with brain weight and metabolic rate suggest that the significance of cycle length has not been sufficiently explored.