Circadian rhythms, and with them sleep, can be broken in anyone. It is enough to stay up late at the computer or fly a couple of thousand kilometers from east to west (or vice versa).

Mutations in the " Interestingly, in older people, both sleep disturbances and metabolic disturbances occur simultaneously. Most likely, it is somehow connected.

The truth and myths about the sleep of older people Older people often note daytime sleepiness in themselves, and therefore it is believed that they have a disturbed night's sleep. However, a study of two groups (the first of 30 men and women with an average age of 25 years, the second of 23 23 with an average age of 83 years) showed that older people only think that they feel drowsiness more often and stronger than youth.

Participants passed a test to determine the frequency of periods of latent drowsiness during the day (Multiple Sleep Latency Test). This technique is aimed at identifying increased daytime sleepiness, and testing on it is carried out necessarily in the daytime.

During the whole day, the subject is asked 5 times to fall asleep on the bed in a darkened room. This quest must be completed in 20 minutes.. If the subject managed to fall asleep, then after 15 minutes of sleep he is awakened and asked to leave the room for two hours. If after twenty minutes it was not possible to fall asleep, you still need to leave the room and go into it after two hours.

During each attempt, the study participant takes an electroencephalogram, an electrocardiogram, and also measures the frequency of respiration and heartbeat. Such a comprehensive (polysomnographic) analysis allows you to identify how much time it took a person to fall asleep, and what stage of sleep he was in during another attempt.

The results for the older group were unexpected:.

During the test, they fell asleep as often and as quickly as young. True, the older participants themselves seemed to fall asleep faster. It turns out that 80–90-year-olds experience drowsiness no more often than young people, even if they themselves think otherwise.

Drowsiness is not the only parameter of sleep and wakefulness, and the fact that old people really want to sleep no more often than their grandchildren does not mean that there is no difference between the sleep of these two age categories.

Differences in normal circadian rhythms in young and old, of course, are. For example, in one study, two groups of healthy volunteers (18–32 years old and 60–75 years old) slept at home for a week, but spent most of the day in the laboratory. Each day, subjects noted when they went to bed and when they woke up.. In addition, once every one and a half hours, the study participants measured body temperature, as well as the content in the urine of cortisol and 6-sulfatoximelatonin.

Cortisol is often called the stress hormone, as it is especially released during difficult life situations.. Nevertheless, the intensity of its production and in conditions good for the body changes during the day.

Most cortisol is formed in the morning immediately after waking up - at 8–9 hours. During the day, its blood content gradually decreases, although unevenly: after eating, the level of cortisol temporarily rises, but not as much as in the morning.

6-sulfatoxymelatonin is a metabolic product of melatonin, the main " By the daily change in the concentration of these two hormones, you can track the progress of circadian rhythms in humans.

Picture 1. Daily fluctuations in the concentrations of melatonin, cortisol and growth hormone. The horizontal axis represents the time of day, the vertical axis shows the concentration of the hormone in mg / dl (deciliter, 100 ml).

It turned out that young subjects later go to bed, but fall asleep faster. It takes them about 45 minutes to fall asleep versus the 95 minutes usual for older. Seniors sleep an average of two hours less.

The peak concentration of 6-sulfatoximelatonin and cortisol in urine in representatives of the older age group occurs earlier in time of day than in young. However, the correlation between the change in the content of these two hormones and the time of waking up and falling asleep in people 60–75 years old is slightly weaker than in people 18–32 years old.

It turns out that in the elderly, the time of sleep and wakefulness is somewhat shifted relative to circadian rhythms. It is known that not only the total duration of sleep is important, but also what its phases manage to go through during the night.

Conventionally, sleep can be divided into two phases that change each other several times during the night: fast sleep (fast microwave, paradoxical, stage of fast eye movements - BDG, rapid eye movement - REM); slow (non-REM sleep; divided into four stages: falling asleep, shallow sleep, deep sleep, delta sleep). The phases differ from each other by the frequency of the waves of electrical signals visible on the electroencephalogram (EEG), as well as the degree of muscle tension and the presence or absence of rapid eye movements. Both REM and non-REM sleep are important for normal health..

Animals that were constantly artificially deprived of one of these two phases of sleep did not live very long.. With age, the duration of the REM phase relative to the total sleep time decreases, and the proportion of the first and second stages of the non-REM phase of the total sleep time increases. But the relative duration of the fourth stage, delta sleep, is reduced. REM sleep is traditionally associated with dreams.

Since the proportion of this phase of sleep in the elderly decreases, the ability to remember one's dreams should decrease with age. In addition, dreams can be associated with autobiographical memory, and it, like other types of memory, worsens in old age.. Both of these assumptions are confirmed by an online survey of 28,888 volunteers aged 10 to 79 years..

At the third stage of the non-REM phase of sleep, the sigma rhythm is visible on the electroencephalogram, its second name is sleep spindles.

EEG studies show that in older people, the frequency and amplitude of carotid spindles, recorded by electrodes above the frontal lobes of the cortex, decrease compared with similar indicators in young. For each lead (electrode) of the EEG, you can build a graph of the frequency of occurrence and amplitude of the sleep spindles, and from it to judge the progress of aging.

Probably, knowing the age-related dynamics of carotid spindles in a particular person, in the future it will be possible to identify pathologies of metabolism and intelligence at an early stage. Physiological age-related changes in sleep and metabolism, as well as their disorders. Consider the changes in the physiology of sleep, which in old age manifest in any person without noticeable health problems.

Of course, hormones and neurotransmitters are involved in the regulation of the state of the body, including those that are rarely heard. Here is a list of them:.

The production of orexins, the neuropeptides secreted by a number of hypothalamic cells, decreases with age (the fact is that these cells die off over time). Orexins maintain a state of wakefulness, and a significant lack of orexin leads to narcolepsy - sudden attacks of irresistible drowsiness during the day. Apparently, one of the reasons why the quality of sleep in older people is worse than in young people is because they have less orexin. The quality of sleep falls because orexin does not just prevent a person from falling asleep. It softens the transition between sleep and wakefulness and can be said to make it smoother and more predictable.. Agree, to understand when you fall asleep is somehow nicer than to "

Adenosine - one of the non-classical mediators that cause drowsiness. Adenosine is, in fact, part of the molecule’s “universal energy currency of the cell” - ATP, only without phosphate ions and without energy-rich chemical bonds. The longer the person did not sleep, the more energy he spent, and the higher the concentration of adenosine in his blood. You can artificially reduce the sensitivity of cells to adenosine and temporarily drive away fatigue by taking an antagonist of its receptors - caffeine. With age, in the cerebral cortex, the balance of activity of enzymes that help synthesize adenosine and enzymes that help convert it into the form of adenosine phosphates changes: the former begin to work significantly more than the latter. Because of this, the level of adenosine in the brain rises.. This is probably why older people often feel sleepy, albeit "

If we consider age-related changes in sleep not at the level of cells and hormones, but more globally, this is what. With age, night sleep becomes fragmented, a person often wakes up, so the overall quality of sleep falls, even if you go to bed briefly during the day. In fact, this is a manifestation of nighttime insomnia.

Insomnia is often found in older people, but a large age alone does not increase its likelihood.. Such risk factors increase it: depression (especially often occurs after 65), the death of a spouse, retirement, the onset of dementia (see dementia. next section). The manifestations of insomnia are also enhanced by alcohol and medications often used by old people: antidepressants, carbidopa and levodopa (they are prescribed for the treatment of parkinsonism), adrenaline beta-blockers (from heart diseases; can cause nightmares) and corticosteroids.

With insomnia and fragmented sleep, glucose metabolism may be impaired. It occurs because the concentrations of ghrelin and leptin - “saturation hormones” —are changing, as well as the sensitivity of cells to the most important “glucose hormone” - insulin (by the way, it also depends on circadian rhythms). Regardless of the total sleep time in people of the same age, a larger proportion of slow-wave sleep correlates with lower body weight and lower risk of obesity.

Periodic movement of the limbs during slow sleep is associated with an increased risk of cardiovascular disease and stroke. It’s only important to understand that this relationship is qualitative, not quantitative.. For example, it is impossible to predict how quickly and with what probability a person will have a stroke by the intensity of limb movements during sleep, because the latter can be not only a consequence of sleep pathology, but also its cause.

Often, health problems manifest themselves as breathing problems during sleep: snoring, sleep apnea, etc.. They appear as a result of disruption of the bridge neurons. The bridge is the part of the brain where one of the “centers of wakefulness” is located - the reticular formation, the accumulation of neurons that support the body’s activity in tone, at the level of wakefulness. Not far from them is the respiratory center. Therefore, with problems with one group of nerve cells, the second often suffers.. Fortunately, during waking hours, the vast majority of patients with such problems do not show serious breathing problems..

Sleep and intellectual impairment in old age.

Sleeping is also important because during the slow wave stage and the REM stage of sleep, memory consolidation occurs - the transfer of information from short-term memory to long-term. The hippocampus plays a key role in this process..

The information that a person received while awake is “lost” several times in a dream in the form of a sequence of electrical impulses in the hippocampal cells, and then transmitted to the cerebral cortex (mainly to the prefrontal), where it remains for long-term storage. The transfer of information from the hippocampus to the prefrontal cortex during sleep is facilitated because the concentration of cortisol and acetylcholine (substances that inhibit memory consolidation) in the brain is reduced.

Figure 2. Age-related changes in the activity of signal transmission from the hippocampus to the cerebral cortex during sleep. With aging, the proportion of slow-wave oscillations in the total sleep time decreases, the prefrontal cortex gradually degrades, the level of cortisol increases, and the concentration of acetylcholine decreases.

In old age, the process of memory consolidation goes with less intensity due to the three features that are already mentioned above:.

the proportion of delta sleep in total sleep time decreases;

increased cortisol production;

the structure of the prefrontal cortex changes, its volume becomes smaller with age.

Nevertheless, in elderly people who do not suffer from serious mental and intellectual impairments, sleep has no less significance for memory consolidation than for young people.

For example, the task of remembering the location of objects, both of these categories of people perform better after sleep. This cannot be said for older people with cognitive problems..

With motor memory, the situation is somewhat different.. Even healthy elderly people do not help sleep better remember recently learned motor skills. The exact reasons for this are unknown.. Perhaps the fact is that in old age, the memorization of sequences of movements in any case worsens, and against the background of this deterioration, the "

Neurodegenerative diseases and sleep.

The most famous neurodegenerative diseases are Alzheimer's disease, and Parkinson's disease is most common.. Unfortunately, their fame is sad. In Alzheimer's disease, amyloid beta plaques accumulate in neurons, and in Parkinson's disease, Levy bodies (alpha synuclein) form in neurons. The amount of amyloid in this case correlates with the quality of sleep in healthy people aged 60–65 years. However, it is not a fact that sleep disturbances occur due to the increased content of this protein in neurons.. The opposite is also not proven: there is no reason to argue that lack of sleep provokes Alzheimer's disease. However, early-stage Alzheimer's disease can potentially be diagnosed with sleep disorders.. This fact is also supported by the fact that with the intensification of the symptoms of this dementia, the severity of sleep disorders increases (the same goes for dementia with Levy bodies, a disease that resembles Parkinson's disease with some symptoms and Alzheimer's disease with some others. ) In addition to this, despite frequent jerking, in patients with Alzheimer's dementia, the duration of sleep is significantly reduced.

In Parkinson’s disease, sleep becomes intermittent, the REM phase of sleep is disturbed, the frequency of sleep spindles and the duration of slow-wave sleep are reduced, and daily fluctuations in the level of cortisol are smoothed out. It turns out that in parkinsonics sleep and wakefulness are not clearly divided into periods, the borders between them are erased to some extent.

Huntington's chorea has fragmented sleep and wakefulness. A person is active at night and falls asleep late. He has a reduced proportion of REM sleep, an increased frequency of carotid spindles, during stage 1 of non-REM sleep chorea can be observed - chaotic uncontrolled movements of the limbs, the main manifestation of this disease during wakefulness. With ALS (amyotrophic lateral sclerosis) there are respiratory disorders in a dream. REM sleep becomes intermittent, and the proportion of slow wave sleep is reduced. In addition, the course of daily fluctuations in cortisol is disrupted.. It is interesting that the manifestation of almost all of the above sleep disorders can be reduced by phototherapy (periodic exposure to bright light) and organized (not uncontrolled! ) taking melatonin.

Conclusion: So, circadian rhythms and sleep are inextricably linked with aging and all its attendant attributes.. Probably someday, having influenced one thing, we will be able to change the other: for example, we will cure sleep problems in a person suffering from a neurodegenerative disease, and his level of intelligence will stop decreasing, thereby his active life will last. Maybe someday we will be able to reduce the negative impact of lack of sleep on the likelihood of developing cancer and will be in time more without the risk of dying from cancer. At the worst, we will begin to recognize Alzheimer's disease or Huntington’s chorea in the early stages by violations of fast-wave and slow-wave sleep. Everything that is studied for human health, all for the better.

nedug. ru.