SLEEP: These neurons trigger deep sleep

 This work from the Beth Israel Deaconess Medical Center (Boston) identifies a “sleep switch” in the brain, which is involved in a subsidiary way in the regulation of body temperature. Very special neurons, documented in the journal Nature Communications, because when they are activated, the subject - here the mouse - is plunged into a deep sleep. A potential target, therefore, to treat sleep disorders.  

 

About 20 years ago, the same team had already suggested that this set of nerve cells could play a key role in the onset of sleep. The team is doing it again with this new research, demonstrating in mice that these cells are indeed essential for normal sleep. It is in fact the first test that comes to activate these cells, located in a region of the hypothalamus called the ventrolateral preoptic nucleus (VLPO). And the researchers show that the activation, by laser (light) or drug (chemical activation), of these “VLPO neurons”, leads to deep sleep.

 

These new results confirm previous findings by the team, led by Dr. Clifford B. Saper, Chairman of the Neurology Department of the (BIDMC), that damage to these neurons can cause insomnia. One research in particular, conducted in elderly people who “lost” their VLPO neurons during the natural aging process, showed that these people suffered from insomnia.

 

In "normal times", these VLPO cells are stimulated 1-4 times per second, which induces sleep. If these cells are stimulated faster, they eventually fail to fire and stop functioning. Thus, activating them 10 times per second causes their function to stop completely. Finally, normal activation of VLPO cells also causes a drop in body temperature, which makes sense, since body temperature drops slightly during sleep, when VLPO neurons fire.

 

However, with continued activation, here in mice, body temperature drops very low, down to 5 or 6 degrees Celsius. The authors hypothesize here that excessive activation of these same neurons could be responsible for prolonged sleep and lower body temperature in hibernating animals…

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SLEEP: Less screen time helps children's mental abilities

 Regular physical activity improves physical and mental health. Conversely, is screen time unfavorable to cognition? Studies are mixed on the subject, but all agree on the importance of limits in children. "Limiting children's screen time is linked to better cognition", reaffirms this very large Canadian study presented in the Lancet Child and Adolescent Health.

 

Researchers from the Children's Hospital of Eastern Ontario Research Institute, the University of Ottawa, Carleton University (Canada) followed 4,524 children from the United States, selected from 21 different sites. Their analysis concludes that less than 2 hours of screen time per day is associated with better cognitive test scores.

 

Less than 2 hours of screen per day? In fact, it was a good idea for this team to assess whether the Canadian recommendations on screen time, sleep and physical activity in children aged 8 to 11 are indeed favorable to mental function, as assessed by a series of tests. These recommendations limit all-screen time to less than 2 hours per day, recommend getting 9 to 11 hours of sleep per night and practicing at least 1 hour of moderate to vigorous physical activity per day. The analysis shows that:

• the children who have the best test results are also those who observe the 3 recommendations;
• however…only 5% of children follow these 3 recommendations; the association identified is therefore not statistically significant or borderline;
• children engage in approximately one hour of physical activity on average 3.7 days per week, use screens on average 3.6 hours per day and sleep on average 9.1 hours per night;
• just over half of the children met the sleep recommendations, while 37% met the time recommendation and only 18% met the physical activity recommendations.
•  
• screen time and sleep accounted for about 22% of the variation between test scores, while physical activity alone did not appear to be related to mental functioning. This suggests that physical exercise would not be an independently favorable factor for cognition (?).
• finally, logically, other confounding factors such as the school level of the children and the socio-professional level of the household also turn out to be linked to the results of the tests.

 

 

The researchers point out, despite the statistical limit of the results, that parents should consider limiting the time spent by children in front of the screen and monitor their children's sleep and physical activity times. For better cognitive performance.

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DEPRESSION: The antidepressant that also improves sleep

 nsomnia is a common symptom in depressed patients. 70 to 90% of patients suffering from depression also suffer from sleep disorders. These patients have particular difficulty falling asleep or staying asleep. This recent antidepressant, Vortioxetine (VOR), shows, in addition to its effects against depressive symptoms, benefits on sleep, according to this small study conducted in fifteen patients with major depressive disorder and complaining of insomnia. Preliminary data, presented in the British Journal of Clinical Pharmacology, which will have to be confirmed, on the "sleep" benefit by a larger study by polysomnography.

 

This study is conducted on 15 patients with depression and insomnia, who initiated treatment with Vortioxetine for their depressive symptoms. Participants were assessed, at baseline, for sleep (with the Pittsburgh Sleep Quality Index (PSQI) and the Epworth Sleepiness Scale (ESS)) and for depression (with the Beck Depression Inventory (BDI)). The analysis shows, at the end of the follow-up,

• improved quality and continuity of sleep
• the reduction in symptoms of depression is also confirmed to be very significant.

 

Thus, this retrospective analysis showing the significant effect of the drug on depressive symptoms and insomnia in these patients calls for further research. The researchers suggest that the mechanism of action of Vortioxetine, a "multimodal" effect on the transport and reuptake of serotonin, could explain the improvement in subjective sleep, in addition to its effect in reducing depressive symptoms.

Finally, these findings, if confirmed, could have important clinical implications due to the frequency of sleep disturbances in patients with depressive disorder and the insomnia-depression vicious circle effect.

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SLEEP APNEA: Duration of sick leave predicts risk of death

 Duration of respiratory arrest predicts mortality risk in obstructive sleep apnea syndrome (OSAS), but not as one might imagine, concludes this study from Oregon Health & Science University. Research published in the American Journal of Respiratory and Critical Care Medicine reports that participants with short apneas and hypopneas (stopped breathing and “shallow” breathing, respectively) are at increased risk of death at 10 years.

 

Previous studies have shown that the apnea-hypopnea index, a widely used measure of apnea severity, is linked to mortality and heart disease. However, according to these researchers, this measure remains crude and is not a good predictor of risk for women. The study indeed shows that the duration of abnormal respiratory events could be a much more reliable predictor of mortality risk in men and women. In addition, the measurement is simple to determine, using the same polysomnography studies as those currently carried out.

 

The researchers analyzed the records of 5,712 adults, average age 63, participating in the National Heart, Lung, and Blood Institute (NHLBI)'s Sleep Heart Health Study and followed for 11 years. The analysis shows that:

• participants with closer breathing have a 31% increased risk of death;
• this association is strongest in participants with moderate sleep apnea: in this group, the risk of death is increased by 59%.

 

The result is obviously counter-intuitive., because "one would expect that long interruptions of breathing would induce a more severe prognosis, but it is quite the opposite", comments the main author, Dr Butler, professor at the Institute of Sciences of Oregon Occupational Health: "Shorter periods of breathing disturbance indicate a low threshold of arousal, associated with sleep fragmentation, elevated sympathetic tone, and increased risk of hypertension." Moreover, these results suggest that there may be several mechanisms by which sleep apnea leads to increased mortality.

The study does not demonstrate the causal link between shorter breaths and death. These shorter interruptions could be a marker of underlying issues leading to increased death tolls, rather than the cause itself.

 

However, the duration of respiratory disturbances does appear to be a significant predictor of mortality risk.

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SLEEP: Its duration also regulates hydration

 The effects of too short a sleep are multiple, including daytime sleepiness, mood disorders and even metabolic disorders. This study from the Pen State highlights a new harmful effect of lack of sleep, dehydration. Work, presented in the journal Sleep Health, which shows the association of less than 6 hours of sleep per night with the risk of dehydration.

 

In practice, these results suggest that after a night of poor sleep or after sleep deprivation, it is recommended to stay well hydrated.

 

Researchers studied the impact of sleep on hydration and the risk of dehydration in more than 20,000 American and Chinese adult participants. In both population groups, adults who reported sleeping 6 hours per night showed urinary markers of dehydration vs. participants reporting sleeping about 8 hours per night. Specifically, too short a night's sleep is associated with a 16-59% increased risk of dehydration.

 

The body's hormonal system regulates hydration: vasopressin, a hormone, is released to help regulate the body's hydration status. This hormone is released throughout the day, but both earlier and later in the sleep cycle. “So waking too early reduces the window for optimal release of the hormone, which disrupts hydration in the body,” says lead author Dr. Asher Rosinger, professor of biology at Penn State.

 

The Consequences of Dehydration: Dehydration negatively affects many body systems and functions, including cognition, mood, physical performance, and others. Chronic or long-term dehydration can lead to more serious problems, such as an increased risk of urinary tract infections and kidney stones.

Admittedly, this is an analysis of observational data and cross-sectional studies, so the results do not demonstrate the cause and effect relationship. However, it reveals a strong association between sleep and hydration.

 

A sufficient duration of sleep is associated with a good regulation of the hydration of the body and, after an insufficient duration of sleep, it is therefore quite simply recommended to think about hydrating.  

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