While much is known about the negative health implications of insufficient sleep, relatively little is known about risks associated with excessive sleep. However, epidemiological studies have repeatedly found a mortality risk associated with reported habitual long sleep. This paper will summarize and describe the numerous studies demonstrating increased mortality risk associated with long sleep. Although these studies establish a mortality link, they do not sufficiently explain why such a relationship might occur. Possible mechanisms for this relationship will be proposed and described, including (1)sleep fragmentation, (2)fatigue, (3)immune function, (4)photoperiodic abnormalities, (5)lack of challenge, (6)depression, or (7)underlying disease process such as (a)sleep apnea, (b)heart disease, or (c)failing health. Following this, we will take a step back and carefully consider all of the historical and current literature regarding long sleep, to determine whether the scientific evidence supports these proposed mechanisms and ascertain what future research directions may clarify or test these hypotheses regarding the relationship between long sleep and mortality.
WHO ARE THE LONG SLEEPERS?How much sleep do we need?Whereas the answer to this question usually involves the determination of the minimum amount of sleep required for the maintenance of health, less attention has been directed to the question of the maximum amount of sleep for optimum health. This may be an equally important issue, given research suggesting that there are negative health consequences of excessive sleep 1 .There is growing public awareness of the need for an adequate amount of sleep, and the myriad problems associated with insufficient sleep, which is consistent with a hypothesis