A Study On The Relationship Between Cognition,emotion And Sleep In Older Adults

With the improvement of people's living standards and the pursuit of a healthy life,sleep has gradually gained more attention from the public.Previous study has found that sleep plays a very important role in maintaining cognitive function and good mood.Insufficient sleep might cause cognitive decline and negative emotions,and chronic sleep deprivation may even lead to cognitive disorders and emotional disorders.With the increasing age,older adults' sleep is undergoing significant changes in structure,quantity and quality.Compared with younger adults,older adults spend more time sleeping during the day,while their nocturnal sleep time decrease significantly with increased sleep latency,decreased sleep efficiency,thus their sleep become fragmented;according to the Manual for Scoring of Sleep and Associated Events published by the American Association of Sleep Medicine,older people generally have longer N1 sleep with shorter N2 sleep,slow wave sleep and rapid eye movement sleep;which means older adults' brain activity during sleep is significantly different from that of younger adults.Previous study has proved that older adults' mood basically remains stable,even showing positive bias with aging.On the one hand,studies related to sleep and emotion showed that sleep,especially rapid eye movement sleep,contributes to the processes of emotion regulation,while the lack of sleep often leads to negative emotions such as depression and anxiety.On the other hand,pre-sleep emotional activities also have a significant impact on nocturnal sleep,it can cause changes in the sleep structure and the brain activity during sleep,so sleep and emotion are related bilaterally.Sleep in older adults is shorter than younger adults with poor quality,but older people's mood remains at a higher level,however,existing studies on sleep and aging rarely explore their relation.Therefore,one of our research purposes is to explore the relationship between sleep and pre-sleep emotional activities and its age effect.Participants were required to watch negative movie fragment before they went to sleep which aimed at activating their negative emotion.The POMS scale was used to measure the emotional changes of both younger and older participants after one night's sleep,besides,all participants' nocturnal sleep was monitored using a actigraphy.The results showed that,compared with younger participants,older adults' sleep became worse after watching negative movie,mainly reflected in reduced sleep time;and after one night's sleep,older adult's emotion became significantly better for their negative emotions reduced more than younger adults.It can be inferred that older adults do not need as much sleep as younger adults do to maintain good mood;in addition,according to the Socioemotional Selectivity Theory,emotional wellbeing is the goal for older people to keep good mood,so they might use more emotional regulation strategy to maintain a healthy emotional state.Due to the interaction of many factors such as physical and psychological factors,the cognitive function of older adults has decreased significantly with aging process,mainly reflected in processing speed,working memory and executive function.Sleep has a protective effect on a variety of cognitive functions,for example,the reactivation during sleep can promote the consolidation of newly formed memory,but the lack of sleep can lead to impairment of cognitive function.Therefore,we can see that sleep has a close relation with cognition.The studies related to sleep disorders and neurodegenerative diseases have proved it.Patients with sleep disorders usually show a decline in cognitive function.For example,cognitive impairment in patients with obstructive sleep apnea syndrome is mainly manifested in attention,memory,and executive function;patients with neurodegenerative diseases are often accompanied by sleep problems,such as parkinsonism in patients with Parkinson's disease.We can infer that changes in sleep physiology caused by aging play an important role in the decline of cognitive function in the elderly.Studies have shown that sleep can promote younger adults' memory of the information in the pre-sleep cognitive activities during sleep;however,there is still a lack of research on the effects of pre-sleep cognitive activities on sleep and its age effects,and whether there is a bilateral relationship between sleep and cognition are not yet clear.Therefore,our research purpose was to explore the relationship between sleep and presleep cognitive activities and its age effect.After being accustomed to the sleep laboratory,participants were required to nap in the sleep laboratory with pre-sleep cognitive activities and without pre-sleep cognitive activities respectively in two days,and their nap were recorded by electroencephalography.By comparing participants' sleep under different experimental conditions,it was found that there was no significant difference in the sleep structure and the EEG energy distribution between the data from the condition of presleep cognitive activities and the data from the condition of no cognitive activities.But there was a significant increase in the energy of large-scale brain networks,showing that pre-sleep cognitive activity has a tangible impact on brain activity during sleep.The results of the two experiments above supplemented and improved the theory from previous researches on the relationship between sleep,cognition,and emotion,and clearly defined their links in aging population.Specifically,the relationship between sleep and cognition,sleep and mood are mutual.On the one hand,sleep promotes and maintains normal cognitive function and good mood;on the other hand,emotion activities before sleep may cause changes in sleep structure,as well as changes in brain activity during sleep,cognitive activity before sleep also increases brain energy and brain activity during sleep.Among aging populations,sleep changes along with aging is an important factor leading to decreased cognitive function,but it still effectively helps with maintaining normal emotional state and promotes reduction of negative emotions.Therefore,both presleep cognitive activities and emotional arousal have a significant effect on older adult's sleep.As many countries around the world have entered an aging society,the health problems of the elderly have gained more and more attention.Sleep problem is an important issue that concerned by many older adults.Researches in sleep of older adults are essential in solving this problem.By studying the relationship between sleep,cognition and emotion,and their age effects,we can provide effective solutions and scientific basis for the prevention and treatment of neurodegenerative diseases and some emotional disorders in aging population.It can also provide suggestions for the improvement of the sleep quality of the elderly,provide theoretical support for healthy aging,and which has a wide range of social significance.However,there are still some lacks in our research.On the one hand,there was no in-depth excavation of the intrinsic mechanism of sleep promoting the decrease of negative emotions in the elderly;on the other hand,the underlying mechanism of cognitive activities' effect on brain activity during sleep is not yet clear.Therefore,there are still many questions remaining unsolved in the relationship between sleep,cognition and emotion during the aging process.However,with the continuous development of scientific research techniques and methods,we believe that in the future we can fully study and discuss these questions.