| dc.description.abstract | The aim of this study was to examine the association between previous night’s sleep and cognitive functions with both subjectively reported and accelerometer-measured sleep, in older adults. In addition, the association between subjective alertness and cognitive functions was investigated. Prior research has examined the association between sleep and cognitive functions mostly with subjective measures of sleep, which are not as accurate as objective measurement methods. Population is growing older around the world, which in addition increases the prevalence of cognitive deficits in the population. In this study, accelerometer was used alongside self-reports of sleep and alertness to measure sleep more objectively.
The study sample consisted of 243 participants (mean age 62.37, SD=1.02; 17 % men) from the Finnish Retirement and Aging study. The participants were public sector workers on the verge of retirement. Sleep was assessed with accelerometer, which gave information about sleep duration and sleep efficacy. In addition, self-reports of sleep duration and the level of alertness were used. Cognitive testing considered several subdomains of cognition: memory, executive function, attention, psychomotor speed, cognitive flexibility, and verbal recall. Cognitive functions were assessed with the Cambridge Neuropsychological Automated Test Battery (CANTAB), the Consortium to Establish a Registry for Alzheimer’s Disease (CERAD) and The Trail Making Test (TMT). Linear regression models were used in the statistical analyses to assess the effects of previous night’s sleep quality and quantity on cognitive functions. In addition, the effect of subjective level of alertness on cognitive functions were assessed. To increase the validity of this study even more, the participants were separated into three groups based on the amount of sleep they had. The groups were: people who slept the same amount as usually (+-30 minutes) on the night before the testing, people who slept less than usually (>30 minutes less) and people who slept more than usually (>30 minutes more).
Subjective alertness was associated with attention switching tasks, and cognitive flexibility when controlling some of the covariates (occupational status, age, gender), although the association for some of the cognitive flexibility tasks diminished to non-significant level after adjusting for more covariates (Body Mass Index, self-rated health, depression, physical activity, the consumption of tobacco and alcohol). When the participants were separated to different groups based on the proportional amount of sleep they had on the night before the testing compared to the average amount of sleep they had on the whole measurement period, the effects disappeared. In the analyses, accelerometer-measured sleep was not statistically significantly associated with any of the cognitive subdomains. In conclusion, the level of subjective alertness may be associated with cognitive flexibility and attention switching when controlling covariates, although further inspection is needed. No statistically significant associations between objectively measured sleeping variables and variables measuring cognitive functions were found in this study. More research is in addition needed to further investigate the relationship between accelerometer-measured sleep and cognitive functions. | |
