The Hormonal Effects of Cumulative Partial Sleep Deprivation in Healthy Young Men Wessel M.A. van Leeuwen 1,2, Mikko Härmä 2, and Tarja Porkka-Heiskanen 1 1 University of Helsinki, Institute of Biomedicine 2 Finnish Institute of Occupational Health, Brain and Work Research Centre MCRTN-CT

What is sleep? Sleep is not a passive state, Sleep is not a passive state, absence of waking Sleep consists of several types of brain activities: NREM and REM Sleep consists of several types of brain activities: NREM and REM - electrical activity of the - electrical activity of the brain is measured using EEG

Sleep Research Society 1997 Sleep Architecture

Is sleep important? All known species sleep All known species sleep - sleep is dangerous, but still all animals choose to sleep Extremely long period without sleep kills Extremely long period without sleep kills Loss of sleep results in bad performance Loss of sleep results in bad performance Temporary loss of sleep is compensated for later (=recovery sleep) Temporary loss of sleep is compensated for later (=recovery sleep)

What happens if we do not sleep? Ability to perform is reduced Ability to perform is reduced - motor performance, memory etc. Mood problems (depression) Mood problems (depression) Increased stress levels Increased stress levels Increased risk for diseases Increased risk for diseases - cardivascular - type II diabetes - obesity?

What is happening to our sleep? Epidemiological argument Epidemiological argument - time spent in sleep is diminishing - time spent in sleep is diminishing

How to study the effects of sleep loss? Acute Sleep Deprivation Acute Sleep Deprivation - short period - complete loss Chronic Sleep Deprivation Chronic Sleep Deprivation - longer period - partial loss - more common form of sleep loss than acute

Why laboratory experiments? Control of environment Control of environment Controlled group of subjects Controlled group of subjects Concentrate on defined factors Concentrate on defined factors

Our experiment Sleep was restricted to 4 hours per day during 5 consecutive days Sleep was restricted to 4 hours per day during 5 consecutive days

We measured: Stress reactive hormones Stress reactive hormones - Cortisolsaliva - Neuropeptide Ysaliva - Testosteroneblood Cardiovascular risk factors Cardiovascular risk factors - C-reactive proteinblood - Homocysteinblood

NPY HPA-axis

Introduction: Cortisol & NPY Cortisol Hippocampus Hypothalamus damage Negative feedback Chronic stress Memory NPY Pituitary Adrenal Cortex

Results: Cortisol

Results: NPY

Introduction: CRP Inflammation CRP synthesis in liver CRP in blood Removal of toxic molecules Obesity, chronic fatigue, sleep disturbances, etc. Atherosclerotic lesions Risk of stroke and myocardial infarction

Results: CRP

Summary of Results Substance Effect of sleep loss Effect of subsequent Recovery sleep Cortisol No effect NPYDecrease TestosteroneDecrease CRPIncreaseIncrease HomocysteinIncreaseDecrease

Conclusion Restricting our sleep results in more (chronic) stress and a higher risk to develop cardiovascular diseases. Restricting our sleep results in more (chronic) stress and a higher risk to develop cardiovascular diseases.