Disrupted sleep in your 30s and 40s can lead to cognitive problems in later life, scientists say.
As of 2014, an estimated 5 million American adults over 65 were living with dementia, according to the U.S. Centers for Disease Control and Prevention. The most common form of dementia, Alzheimer's disease, represents roughly 60 to 80 percent of dementia cases, but the term also describes a range of other conditions characterized by an impaired ability to remember, think and make decisions.
Sleep is known to play an important role in brain health, and numerous studies have associated sleep disturbance with a higher risk of developing dementia. However, most research to date has focused on the impacts of sleep disturbance and cognitive impairment in older adults.
"Since Alzheimer's disease pathology begins to accumulate in the brain many years before symptoms onset, it's possible that sleep disturbances identified in late life—close to the time when memory loss becomes apparent—[are] actually the consequence of this pathology that has been developing silently over the years," said Yue Leng in a statement.
Therefore, Leng, a professor in psychiatry and the University of California, San Francisco's Weill Institute for Neurosciences, and her team decided to study how disrupted sleep in our 30s and 40s can affect cognitive function later in life.
"Given the long, symptom-free window of Alzheimer's disease and the high prevalence of sleep problems, the understanding of midlife sleep disturbances has significant public health implications," she said.
In a recent study, published in the journal Neurology, the team assessed 526 participants who had completed a sleep examination in their mid-30s and 40s between 2003 and 2005. A decade later, between 2015 and 2016, the same cohort underwent a series of examinations to test their cognitive function.
The researchers divided the participants' sleep quality into three groups according to how fragmented their sleep was. Those with the highest level of sleep fragmentation in their 30s and 40s were more likely to score lower in cognitive tests 10 years later. These low scores were particularly pronounced when measuring executive function, memory and processing speed.
"This confirms previous studies of older adults suggesting a strong association between sleep disorders and executive function, which might be due to the influence of sleep on the prefrontal cortex area, the seat of executive function, rather than verbal memory," Leng said.
Previous studies have shown that approximately 30 percent of Alzheimer's cases could be prevented or delayed by making lifestyle changes before the onset of clinical symptoms.
"This research contributes to a body of literature that underscores the need to evaluate modifiable risk factors associated with cognitive aging," a senior author of the paper, Kristine Yaffe, said in a statement.
She continued: "Future research is needed to study the link between sleep disturbances and cognition at different stages of life and to identify whether there are critical life periods when sleep is more strongly associated with cognition. This might open up new opportunities for the prevention of Alzheimer's in late life."
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About the writer
Pandora Dewan is a Senior Science Reporter at Newsweek based in London, UK. Her focus is reporting on science, health ... Read more
