Is Balance Control Affected by Sleep Deprivation? A Systematic Review of the Impact of Sleep on the Control of Balance.

Background: Sleep is a complex physiological function that should be addressed from different perspectives and consider the circadian rhythm. Sleep deprivation, either acute or chronic, negatively affects several functions, including motor control. Balance control is essential in several daily life activities and balance problems are related to falls. Research Question: This review focuses on how sleep conditions impact balance control. Methods: Systematic literature review according to PRISMA guidelines. Results: The literature provided strong evidence that acute sleep deprivation impairs postural control. Chronic sleep deprivation as well as low sleep quality had similar effects, although there is a lower number of works addressing this issue. Furthermore, time awake worsens postural controls and it can be used to detect sleepiness and fatigue. The sleep deprivation showed a stronger negative effect on postural control when removing the visual information (eyes closed) than when reducing proprioceptive feedback (soft surface). There is scarce literature about the effects of chronotype, circadian patterns and chronic sleep deprivation, a frequent problem, on balance control; however they consistently indicate that there is an relationship between them. Most of the studies only consider one-night (acute) sleep deprivation without monitoring prior sleep conditions and the circadian rhythm phase of the participants. However, a few studies indicated that these factors must be considered. Significance: These results suggest that the sleep conditions of a subject should be considered for several days prior to balance control tests. Therefore, we propose a revision of current postural measurement protocols to include sleep assessment, such as sleep quality questionnaires or actimetry, and to consider the circadian rhythm of the participants to plan the hour of the tests.

Comparison of sleep quality assessed by actigraphy and questionnaires to healthy subjects.

Sleep quality analysis is crucial for human health and it is related to duration, rhythm and quality. The goal of this study is to analyze objective assessment of the sleep-wake cycles with actigraphy, subjective questionnaires and their relationship with sleep quality indices. A wearable actigraph registered the sleep habits of 41 healthy subjects for 9 days. Afterwards, the subjects filled two questionnaires about sleep quality (Pittsburgh Sleep Quality Index) and sleepiness (Epworth Sleepiness Scale). The subjects were divided into two groups based on cut-off scores and the actigraphy parameters were compared between groups. Group 1 in ESS and PSQI categorization had less diurnal sleepiness and better sleep quality, respectively, than Group 2. Measurements of regularity (IS), fragmentation (IV), active phase amplitude (M10), rest amplitude (L5), and relative amplitude (RA) were compared between groups. Group 2 had higher L5 values. Parameter L5 (lowest of 5 consecutive hours of activity) was concluded to be relevant to identify the sleep conditions of the subjects.

Social jetlag impairs balance control.

We assessed the impact of a common sleep disturbance, the social jetlag, on postural control during a period involving workdays and free days. The sleep habits of 30 healthy subjects were registered with a wrist actimeter for nine days (starting on Friday) and they participated in a set of four postural control tests carried out on Friday and on Monday. In addition, the subjects filled questionnaires about their sleep conditions and preferences. Actimetry measurements were used to calculate the Mid Sleep Phase (MSP). The difference between the MSP values on the workdays and free days measures the social jetlag. There were significant differences in sleep variables between workdays and free days. Postural control performance improved on Monday, after free sleep over the weekend, when compared with the tests performed on Friday. It seems that social jetlag affects brain areas involved in the control of posture, such as thalamus and the prefrontal cortex as well as the cerebellum, resulting in a worse performance in postural control. The performance improvement in the posture tests after the free days could be attributed to a lower sleep debt.

Análise da ritmicidade circadiana nas transições do horário de verão

O ciclo claro/escuro gerado pela rotação da Terra tem uma duração razoavelmente regular ao longo ano todo, mas a duração do dia e da noite se altera com o passar das estações, sendo que no inverno a fase clara do dia é mais curta e no verão mais longa e a fase da noite vice-versa. Com o objetivo de tirar um maior proveito da luz solar nos dias mais longos, foi criado o horário de verão, caracterizado pela mudança em uma hora do relógio. Apesar de haver uma suposta economia de energia elétrica no período de vigência do horário de verão, a mudança brusca de horários é um grande desafio temporal que gera diversos problemas de saúde associados a distúrbios de sono e comportamentais como desanimo. O nosso objetivo foi estudar o processo de adaptação dos ritmos circadianos diante da mudança do horário do relógio nas transições do horário de verão brasileiro. A observação dos nossos dados revela que há desorganização temporal interna e externa e que os padrões circadianos da atividade e temperatura seguem predominantemente os horários do ciclo claro/escuro, e não do relógio social, exceto no início do HV, quando é observado um mascaramento da atividade. A desorganização temporal ocasionada pela mudança do relógio observada no presente estudo pode estar associada com diversos problemas de saúde e sociais relatados em outros estudos, como distúrbios de sono, problemas de atenção durante a vigília e aumento de acidentes automobilísticos. Como a política do horário de verão tem uma abrangência mundial, os efeitos dessa medida administrativa compromete a qualidade de vida dos seres humanos de todo o planeta e talvez não seja uma vantagem econômica quando se coloca na equação a saúde humana