Poor sleep linked to reduced memory in older adults, study shows

Variability in night-to-night sleep time and reduced sleep quality adversely affect the ability of older adults to recall information about past events, according to a new study by researchers at the Georgia Institute of Technology and published in Frontiers in Human Neuroscience.

The research, supported by a National Science Foundation Graduate Research Fellowship, included 81 volunteers from the Atlanta, Georgia area. The volunteers were evaluated carefully to screen out those who had mild cognitive impairment or other potentially confounding factors. Younger adults were recruited in the age range of 18 to 37 years, while older adults were recruited in the range from 56 to 76 years. Ultimately, 50 adults were selected for the study, according to the study abstract.

Led by Audrey Duarte, PhD, an associate professor in the School of Psychology and principal investigator in the Memory and Aging Lab, researchers looked at lifestyle factors to see how people sleep normally, and how their sleep patterns change over time. Participants were accelerometers worn on their wrists to measure sleep duration and quality over a period of seven nights. Though they did not measure brain waves, the devices allowed sleep measurements to be done in the participants' own homes. The researchers sought to provide a more realistic measurement than testing done in sleep labs, which typically lasts just one night.

Participants were asked to visit a Georgia Tech laboratory for a memory test that measured electroencephalography (EEG) brain wave activity as they attempted to recall word pairs that had been shown to them earlier.

Results showed that night-to-night variability in the older study participants had a major impact on their performance in tests aimed at evaluating episodic memory, Duarte said.  The study also found unexpected racial differences in the type of sleep patterns tied to lower memory performance across both younger and older African American research participants.

The study found that black adults slept for 36 minutes less than other adults, which translated into a 12% decrease in memory-related brain activity. On an average night, black adults in the study spent 15 minutes more time awake after falling asleep than did other participants. The study also found significant variation among subjects in each age group, Duarte said.

Although further investigation will be needed to confirm the results of the pilot study, the findings could help open a new area of research aimed at understanding the potential connection between poor sleep and the memory declines associated with aging. The study also underscores the importance of sleep in maintaining good cognitive functioning, researchers said.

"You can imagine that many people, students among them, may have variable sleep patterns based on staying up late to study and sleeping in on weekends to catch up," Duarte said. "This data shows that may not be the greatest strategy for optimizing memory ability."

In future studies, researchers said they hope to expand their study to a larger group of participants, to study the relationship between sleep and memory in other underrepresented minorities, and to explore whether variations in sleep patterns could predict a person's likelihood of experiencing diseases such as Alzheimer's.

The study's takeaway message may be that regular sleep is important at any age for the best cognitive performance, Duarte said. Yet improvements in sleep may be one area where people concerned about cognitive impairment may have an opportunity to make improvements.

"In understanding normative aging, lifestyle factors are a good area to target because they are potentially factors [that] we can control," said Duarte. "It's been known for decades that important things are happening while you sleep with regard to memory consolidation and strengthening of memories. Because we knew that sleep quality typically declines in normal aging, this was a prime target for study."