Não é de hoje que problemas de sono são tratados como um problema que afeta uma boa parte da população. Por isso existe os instrumentos da medicina do sono para suportar os profissionais da área.
In 2003, a study stated that about 70 million citizens of the United States of America suffer from some type of chronic sleep deprivation or restriction. This number would correspond to almost a quarter of people in the country, that is, for every 4 people, one would suffer from some type of sleep problem. (NHLBI (National Heart, Lung, and Blood Institute). 2003. National Sleep Disorders Research Plan, 2003. Bethesda, MD: National Institutes of Health).
The consequences can be very serious, both for health and for social life, encompassing performance problems in daily tasks, encompassing study and work activities. In an economic context, it is estimated that, in the United States of America alone, sleep disorders generate an economic impact of more than 400 billion dollars annually.
These economic problems are related to several causes in which sleep has a direct impact, from traffic accidents, in which drivers end up sleeping while driving, to a higher prevalence of accidents at work in individuals who are more sleepy. Even health professionals are not left out of this statistic: night shift staff make three times more medical errors than individuals with a regular work schedule.
It is clear that maintaining good sleep habits is important. But how do you do that nowadays?
Due to the COVID-19 pandemic, many people began to report more sleep problems. In a census carried out worldwide for the 2021 World Sleep Day, it was observed that about half of the population is not satisfied with their sleep routine, and in the general average, people sleep about 6.9 hours per night during weekdays – values that are lower than those recommended by WHO as ideal for a good night’s sleep.
Mas o que acontece quando se dorme pouco?
Sleep stages are usually grouped into cycles, which are repeated throughout the sleep phase of individuals, changing their pattern over time. In a night of sleep for individuals with healthy habits, these cycles are repeated four to six times.
The standard method for detecting sleep problems is polysomnography (PSG). From the PSG analysis it is possible to identify structural sleep parameters, which are based on the pattern of brain waves from the electroencephalogram, muscle activity and oculogram. (Douglas et al. 1992)
From these data, it is possible to characterize each stage of sleep, which are divided into five distinct events:
- In stage 1, there is a presence of brain waves of low frequency and amplitude (theta waves), decreased muscle activity, breathing and heart rate, in addition to low eye movement.
- Stage 2 is characterized by the presence of the K complex, sleep spindles and absence of eye movements, with heartbeat and breathing decreasing further, with greater muscle relaxation.
- In stages 3 and 4, waves of large amplitude and low frequency (delta waves) are present. Known as deep sleep, it is this stage that will generate the sensation of restful sleep, having a longer duration in the first half of the sleep phase.
In REM sleep, also known as paradoxical sleep, there is a marked reduction or absence of muscle tone, rapid eye movements and saw tooth waves, similar to that of wakefulness. It is in REM sleep that most dreams occur, and this step is very important for consolidating memory, learning and other cognitive processes.
The reduction in sleep duration can generate cognitive deficits that are associated with loss in the stability of the sleep structure. Recent studies demonstrate that cognitive deficits involving aspects of memory, learning and attention may be associated with a change in the sleep patterns analyzed by PSG (Alhola and Polo-kantola 2007; Fullagar et al. 2015; Neu and Linkowski 2010; Thomas et al. 2000b).
Additionally, from the data from the polysomnography, it is possible to assess whether the individuals have a satisfactory total sleep duration, since it is possible to detect the stages and to identify if there are no abrupt breaks between them (Michaelson et al. 2006; Su et al. 2004).
The major problem involving polysomnography studies is the inability of longitudinal monitoring in people’s natural routine. These tests are usually done in the laboratory environment with several connected instruments that can make sleeping very difficult, and it is not possible to follow up over several consecutive days. In addition, as it is a very specific exam, the offer of this exam is not so comprehensive, and has a cost that may be inaccessible to a large part of the population.The major problem involving polysomnography studies is the inability of longitudinal monitoring in people’s natural routine. These tests are usually done in the laboratory environment with several connected instruments that can make sleeping very difficult, and it is not possible to follow up over several consecutive days. In addition, as it is a very specific exam, the offer of this exam is not so comprehensive, and has a cost that may be inaccessible to a large part of the population.
To solve this problem, portable devices can be used to perform a polysomnographic examination, more simply, in the home environment. Recent studies demonstrate that portable EEG equipment, such as DREEM, is capable of generating hypnograms in an automated way, in which it is possible to detect the stages of sleep, with an accuracy that can reach more than 90% when compared to analysis carried out by specialists. (Arnal et al. Date unknown; Kanbi 2020).
The much lower cost when compared to conventional equipment, the ease of use, and the possibility of having the raw signals are positive points that favor using this equipment in longitudinal collections with monitoring outside the laboratory environment.
But although it is a device that has the option for the end user, it is still something that should be worn on the head during the sleep phase, which can be annoying to most users, in addition to analyzing only the sleep stage. Although sleep occurs at night, this phase is totally linked to the waking phase, and the complete study of the sleep / wake cycle generates more information on how the temporal organization of the rhythm of the sleep / wake cycle of the subject happens with the influence of the stimuli from the environment.
In order to assess sleep and circadian rhythmicity, subjective methods such as sleep diaries and activities are commonly used. However, these tools have the problem of depending on the patient / subject’s declared response, which may compromise the results. A more objective tool for monitoring daily activity is the use of actimeters.
A actimetria ou actigrafia é um método não-invasivo para analisar o ritmo sono-vigília por longos períodos, de dias a meses. É baseada no monitoramento contínuo dos movimentos do usuário de forma a identificar fases de atividade e descanso. A grande vantagem da actimetria é a de fornecer informação dos hábitos do indivíduo no seu ambiente natural por um longo período de tempo (Martin and Hakim 2011).
When talking about activity monitors, there is a list of equipment that perform these procedures aimed at the end user. When searching Play Store or App Store on an Android or iOS smartphone, it is possible to find some apps, both free and paid, that intend to record and analyze both sleep and activity level during the day. However, relying on a cell phone can be a complicated task – either due to the autonomy of the device, or even the difficulty of carrying it all the time.
Another problem that must be considered is that, although most devices have accelerometers, which are the devices used to record movements, there is no standardization of models, thus compromising the reproducibility of results when using different devices.
But even so, the use of apps that monitor activity and sleep has become popular – helped by the growing trend and easy access to smartwatches. Smartwatches, which are produced by large companies involved in smartphone production, such as Apple, Samsung and also by companies focused on monitoring physical activity, such as Garmin and Polar, have developed a series of products that combine the monitoring of the activity of subjects with satellite location data, as well as heartbeat, among other physiological variables that can be used within a monitoring system. Thus, smartwatches seem to be an interesting solution for monitoring sleep and the expression of the sleep / wake cycle in individuals.
Smartwatches can be a good solution for the end user, who wants to follow their daily activity routine without much commitment, as well as know the duration of their sleep. However, the problem of system and hardware variability can affect reproducibility, in addition to that end-user products don’t usually allow a more detailed analysis of the data collected. Thus, the use of actimeters aimed at research and clinical monitoring is essential when it comes to the treatment and initial identification of sleep disorders.
And when we talk about more accurate devices, from the analysis of actimetry it is possible to obtain parameters that characterize the expression of circadian rhythmicity in relation to the rhythm of activity and rest, as indicators of rhythm phase, as well as parameters that quantify levels of activity, rest, potency and stability of circadian rhythm and sleep quality (Gonçalves et al. 2014; Martin and Hakim 2011). The much lower cost when compared to PSG equipment, the ease of use, and the possibility of having the raw signals are positive points that favor this equipment in longitudinal collections with monitoring outside the laboratory environment.
About these devices, some points are very important in the choice of equipment: robustness of the equipment, autonomy, precision and freedom in data analysis.
A device must be reliable and resistant to the subject’s use, since they are generally worn on the wrist. You should also have autonomy without the need to recharge for a long period of time, as many sleep disorders are commonly identified after an analysis of the sleep / wake rhythm of several days. Some authors state that a careful analysis of circadian expression and sleep requires at least 9 uninterrupted days of collection.
It is necessary to have equipment with a high precision and reproducibility of the data collected, which is essential for any clinical diagnosis and research work. And finally, it must provide freedom for the exploration of raw data, given that often a more in-depth analysis by an expert, having the freedom to manipulate the data, selecting specific time windows for the analysis, is crucial for the identification of parameters of sleep in order to characterize the routine of the patients and individuals analyzed.
Additionally, the more information is collected by the same device, the more interesting the analysis will be, and the more results can be explored. When it comes to sleep and circadian rhythm, interaction with ambient light is very important, but often ignored even by researchers in the field. Another aspect is information about the physiological conditions of the organism. Many studies have been carried out and published relating the expression of the peripheral temperature rhythm with the parameters of sleep and wakefulness, in which rhythm stability between the two cycles means a better temporal organization of the individual’s organism. – which consequently means a better quality of sleep and life for the subject.
Based on this information, it is possible to understand and know a little about the tools and devices that are most commonly used for the assessment of sleep and the detection of disorders related to sleep problems or circadian rhythm. Depending on the need, cost benefit, and reliability of use, it is up to you to evaluate and choose the ideal equipment for your professional use.