Elsevier

The Lancet

Volume 354, Issue 9188, 23 October 1999, Pages 1435-1439
The Lancet

Early Report
Impact of sleep debt on metabolic and endocrine function

https://doi.org/10.1016/S0140-6736(99)01376-8Get rights and content

Summary

Background

Chronic sleep debt is becoming increasingly common and affects millions of people in more-developed countries. Sleep debt is currently believed to have no adverse effect on health. We investigated the effect of sleep debt on metabolic and endocrine functions.

Methods

We assessed carbohydrate metabolism, thyrotropic function, activity of the hypothalamo-pituitary-adrenal axis, and sympathovagal balance in 11 young men after time in bed had been restricted to 4 h per night for 6 nights. We compared the sleep-debt condition with measurements taken at the end of a sleep-recovery period when participants were allowed 12 h in bed per night for 6 nights.

Findings

Glucose tolerance was lower in the sleep-debt condition than in the fully rested condition (p<0·02), as were thyrotropin concentrations (p<0·01). Evening cortisol concentrations were raised (p=0·0001) and activity of the sympathetic nervous system was increased in the sleep-debt condition (p<0·02).

Interpretation

Sleep debt has a harmful impact on carbohydrate metabolism and endocrine function. The effects are similar to those seen in normal ageing and, therefore, sleep debt may increase the severity of age-related chronic disorders.

Introduction

Voluntary sleep curtailment has become common. “Normal” average sleep duration has decreased from about 9 h per night in 1910 to about 7·5 h currently1 to create maximum time for work and leisure activities.2 Additionally, to meet the demands of around-the-clock production, many shift workers sleep, on average, less than 5 h per work day.3 Sleep curtailment is purported to be harmless and efficient. It has been suggested that a “normal” night's sleep of about 8 h is composed of a 4–5 h period of core sleep, including most of deep non-rapid-eye-movement (non-REM) sleep, and optional sleep.4 It has been proposed that optional sleep could be progressively removed without inducement of increased daytime sleepiness, mood changes, or detectable decline in cognitive function.4 Some studies have shown that participants could adapt to a progressive curtailment of their usual sleep period by 2–3 h per night with no substantial alterations in mood and vigilance,4, 5 but other studies have provided strong evidence to the contrary.6 Experimental extension of the time spent in bed to 14 h per day over 1 month showed that a normal 8 h night does not meet the sleep needs of healthy young adults, who may carry a substantial sleep debt even in the absence of obvious efforts to curtail sleep.7

No study has assessed the potential health impact of chronic sleep debt. Despite well documented modulation by sleep of metabolic and endocrine regulation,8 immune function,9 and cardiovascular variables,10 the consensus is that sleep is for the brain, not for the rest of the body,4, 11 and that sleep debt has little or no effect on peripheral function.4, 12 We investigated metabolic and hormonal variables in people in whom sleep had been restricted and extended.

Section snippets

Protocol

The protocol was approved by the University of Chicago Institutional Review Board and all participants gave written informed consent.

We included 11 healthy young men aged 18–27 years, who spent 16 consecutive nights in the clinical research centre, during which we restricted and extended the time they spent in bed. On the first 3 nights they spent 8 h in bed from 2300 h to 0700 h (baseline, days B1–B3), for 6 nights they were in bed for 4 h from 0100 h to 0500 h (sleep-debt condition, days

Results

Mean total sleep time during the last 2 nights of each study condition was 7 h 14 min (SE 5 min) at baseline, 3 h 49 min (2) in the sleep-debt condition, and 9 h 3 min (15) in the sleep-recovery condition. The duration of awakenings during sleep time decreased from 29 min (5) at baseline to 5 min (1) during the last 2 nights of the sleep-debt condition and increased to 106 min (14) during the last 2 nights of the sleep-recovery condition (p=0·0001). Adaptation to sleep debt and recovery was

Discussion

Less than 1 week of sleep curtailment in healthy young people is associated with striking alterations in metabolic and endocrine function. Therefore, although the primary function of sleep may be cerebral restoration, sleep debt also has consequences for peripheral function that, if maintained chronically, could have long-term adverse effects on health. Decreased carbohydrate tolerance and increased sympathetic tone are well-recognised risk factors for the development of insulin resistance,

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