Who are the long sleepers? Towards an understanding of the mortality relationship

Abstract

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

Insomnia Symptoms, Sleep Duration, and Disability Pensions: a Prospective Study of Swedish Workers

“…Intuitively, there is a connection between short sleep duration and insomnia symptoms, as was suggested by our research and other studies [10,11,34]. Others have found, on the contrary, increased rates of insomnia in 'long sleepers' [33]. This may reflect poor sleep quality, such as non-restorative sleep, or fragmented sleep, leading to lying in bed for long time periods, rather than sleeping longer.…”

“…Actigraphy-verified sleep time often differs from self-reported sleep duration [33]. Intuitively, there is a connection between short sleep duration and insomnia symptoms, as was suggested by our research and other studies [10,11,34].…”

“…In one recent review it was suggested that 'long sleepers' are characteristically different from 'short or normal sleepers' in a number of domains, including tendency toward depression [33].…”

Sleep duration, lifestyle intervention and incidence of type 2 diabetes in impaired glucose tolerance: the Finnish Diabetes Prevention Study

“…Therefore, whether long sleep represents an increase in actual sleeping time or just increased time in bed cannot be definitely determined. The main underlying causes proposed to potentially explain the relationship have been obstructive sleep apnea (OSA), depression, fatigue, low socioeconomic status, heart diseases, and inactivity (13)(14)(15). Of these proposed factors, sleep-disordered breathing including OSA has been found to be independently associated with insulin resistance (16).…”

Self‐Reported Sleep Duration and Quality and Cardiovascular Disease and Mortality: A Dose‐Response Meta‐Analysis

“…However, guidelines make no specific reference with regard to sleeping beyond the recommended limit. Long sleep duration may be associated with obstructive sleep apnea, heart disease, and failing health19 or may represent a symptom of early “latent” disease preceding a formal diagnosis 20…”