By Andonis Vassiliades
We take sleep for granted. But worldwide statistics on sleep patterns show an alarming trend. We are all sleeping less than the required and recommended seven to eight hours. The average hours of good sleep per night have declined by 25 per cent – from eight hours to less than just over six – in the last 75 years. One in three individuals is now thought to suffer from inadequate and poor sleep.
In line with the early psychological experiments on sleep deprivation, for most people a night’s lack of sleep may just be an unwelcome nuisance which leads to irritability, tiredness, negative moods, low energy or memory problems which will disappear with the next night’s sleep. But advances in medicine, psychology and particularly neuroscience render this commonly held attitude a serious misconception and dangerously ignorant of the facts. For lack of sleep or not enough of it comes with serious health warnings: chronic diseases and mental disorders. Even in good sleepers, scientific research finds that the loss of just one night’s sleep leads to a depletion of the immune system (particularly of our natural protection defences against cancer cells) by as much as 70 per cent.
Lack of good quality sleep has been linked to serious illnesses such as cancers, blood pressure, diabetes, heart disease, strokes, obesity, inflammation, depression, bi-polar disorder, psychotic episodes and a diminishing sex drive to name but a few. The WHO in 2007 classified sleep deprivation (particularly in reference to night shift work) as a probable carcinogen. Alarmingly, as I discuss later, sleep deprivation has also been associated recently with the onset of Alzheimer’s dementia. The effects on health as a result of poor sleep can be so total and overwhelming that in the words of Professor Matthew Walker, a neuroscientist and an expert in the field, ‘no aspect of our biology is left unscathed by sleep deprivation’.
Sleep and the time we spend sleeping are important because in those seven to eight hours of recommended sleep the central nervous system carries out the necessary repairs by removing toxic metabolic wastes which build up in the day and in periods of activity. It cleanses, rids itself of toxic tissue and boosts our physical and mental defences to fight off disease and threats to our wellbeing. Think of this process as a store which is left after a hectic day’s activity in a very untidy, messy and even dangerous state. After closing time, the cleaners come in to put things back in their place, to clean and polish, arrange equipment and furniture in an orderly fashion, sanitise and deodorise by clearing the air of smells and other pollutants so that next day the store is again functional to serve both its owners and its customers. So is the case with sleep. It is a restorative biological process that allows us to regenerate our personal physical and mental resources to function well enough to face the demanding tasks of the next day and the days to come.
In the absence of sleep, particularly when the loss of sleep becomes a vicious circle characterised by habitual behaviour, exhaustion, stress, apprehension and even fear of going to bed just in case we fail to go to sleep, some people attempt various forms of meditation, self-suggestion and relaxation techniques, reading, lights out, music and setting a regular time for bed as a solution to
managing sleep. But for others, either out of failure to achieve the desired end or sheer desperation, the solution is to turn to prescribed hypnotic drugs (e.g. benzodiazepines and antihistamines) as an artificial means to inducing sleep. Although the use of prescribed drugs varies from country to country and is age-related, on average four per cent of people at any time take prescription drugs to help them sleep. This is a ludicrous and growing market which is valued in billions per year.
Controversially, despite these drugs’ well-known side effects of interfering with the natural sleep cycle, causing dependency with regular use which requires higher doses just to maintain the same level of effectiveness, creating lethargic states and contributing to various ailments such as cancer and higher mortality rates, their use may be preferable to the health risks of sleep deprivation. As in the case of high blood pressure, cholesterol and diabetes medications which are known to have adverse effects and contra-indications, their prescription is seen as preferable to the consequences of those ailments if left alone.
Although poor sleep is a characteristic feature of Alzheimer’s sufferers, it has been argued recently that lack of sleep may actually contribute to the onset of Alzheimer’s by robbing the brain of the time needed during sleep to cleanse itself from toxic beta-amyloid protein (A-beta). As I explained earlier, this action during sleep is the brain’s way of cleansing and removing the day’s toxic debris to protect against disease. It is believed that this cleansing action during sleep, which has been called the ‘glymphatic system’, uses cerebrospinal and interstitial fluids which are managed by the glial cells in the brain and the spinal cord and which are shown to be more active during sleeping hours. These fluids clean neurons and carry the toxic waste to the liver for excretion.
Lack of such a cleansing operation due to lack of sleep, allows the accumulation of A-beta plagues around brain neurons which lead to an abnormal concentration of toxic tau protein (known as tangles) inside neurons. Whilst A-beta plagues contribute to cell death, tau protein blocks nourishment and the proper functioning of neurons. As A-beta multiplies and tau protein spreads throughout the brain the resultant destruction, followed by chronic inflammation and atrophy plus other complications (e.g. disruption of levels of the hormone melatonin which is essential for the body to sleep), compromises the proper and normal functioning of the brain and contributes to the characteristic symptoms of Alzheimer’s.
Given our knowledge that sleep deprivation is a common worldwide problem which keeps increasing in magnitude, the parallel galloping increase in the numbers of people afflicted with Alzheimer’s may not be an accidental association. Currently, there are an estimated 50 million people worldwide with Alzheimer’s or other dementias. According to the WHO approximately 10 million of new cases appear each year worldwide. By 2030 the number of cases are estimated to reach 75 million and by 2050, 152 million. The global cost in dealing with Alzheimer’s is put at £480 billion per annum at current prices.
If sleep deprivation is firmly shown, without any lingering doubt that it does contribute to the onset of this most dilapidating disease we should all be concerned. But at the same time the scientific findings offer hope too. They raise the possibility that Alzheimer’s and other neurological pathologies may be preventable or treatable. By gradually understanding better the role sleep plays in keeping people healthy and how the glymphatic system and its cleansing operations work may allow for solutions to counteract the effects of inadequate or poor quality sleep.
Andonis Vassiliades is an emeritus professor