Alzheimer’s already affects more than 46 million people worldwide and the number of cases is expected to have tripled by 2050 if a therapy capable of preventing or curing the disease is not found, according to data from the Pascual Maragall Foundation. and although it generally appears after the age of 65, brain deterioration begins many years before the first symptoms appear.
Poor sleep is one of the risk factors that can contribute to the development of this and other dementias, and now a study has examined the association between the duration and quality of sleep, measured when the participants were between 30 and 40 years old, and the Cognition in midlife assessed 11 years later. The results have been published in the journal Neurology.
The research has been led by the University of California San Francisco (UCSF) and has shown that the quality of sleep, not the quantity, can influence the development of dementia decades before symptoms begin. While previous studies had focused on sleep disorders and cognitive decline in old age, the 526 participants in this research had an average age of 40 years at the start of the study.
“Since the pathological signs of Alzheimer’s disease begin to accumulate in the brain many years before the onset of symptoms, it is possible that sleep disorders identified in old age (around the time when memory loss becomes apparent) “obvious) are actually the consequence of this pathology that has been developing silently for years,” said Yue Leng, from the Department of Psychiatry and Behavioral Sciences at UCSF and the Weill Institute of Neurosciences and first author.
“Taking into account the long symptom-free period of Alzheimer’s disease and the high prevalence of sleep problems, understanding sleep disorders in midlife has important implications for public health,” added this expert.
Fragmented sleep negatively affected cognition
The authors of the work used an activity monitor placed on the participants’ wrist to record “sleep fragmentation” at bedtime, which took into account the amount of time they remained still and the amount of time they were in bed. motion. These scientists recorded the participants’ sleep habits and assessed their cognitive performance years later, and found no association between cognition and sleep duration when analyzing both self-reports and data from wrist-based activity monitors.
In contrast, they found that those with higher levels of fragmented sleep were up to three times more likely to score below average on cognitive tests than those with lower levels of fragmented sleep, when adjusting for factors such as education, depression, body mass index, physical activity, diabetes and hypertension.
“This research contributes to a body of literature that underscores the need to evaluate modifiable risk factors associated with cognitive aging.”
The researchers divided sleep quality scores into three groups: those with highest, moderate, and lowest levels of sleep fragmentation. Participants in the top group were 2.10 to 2.97 times more likely to score below average on four tests measuring executive function, as well as working memory, processing speed, and global cognition, compared to those in the lower group. However, a fifth test quantifying verbal memory showed no differences between these two groups.
“This confirms previous studies of older adults that suggest a strong association between sleep disorders and executive function, which could be due to the influence of sleep on the prefrontal cortex area, the seat of executive function, rather than on the verbal memory,” Leng said.
“This research contributes to a body of literature that highlights the need to evaluate modifiable risk factors associated with cognitive aging,” said Dr. Kristine Yaffe, from the departments of Psychiatry and Behavioral Sciences, Neurology and Epidemiology, and Biostatistics. from UCSF and another of the lead authors.
“Future research is needed to study the link between sleep disorders and cognition at different stages of life and to identify whether there are critical periods of life in which sleep is more strongly associated with cognition,” adds Yaffe, member of the first team of experts to determine that 30% of the risk of dementia can be prevented. “This could open new opportunities for the prevention of Alzheimer’s in old age,” he concludes.
