In a collaborative national study of middle-aged Hispanic adults, physician-researchers with the University of Miami Miller School of Medicine have identified a link between poor sleep patterns and cognitive decline. Taking longer to fall asleep was associated with lower measures of verbal learning, verbal memory and other functions over a seven-year study period.  

“Sleep is a performance-enhancing activity, and we need to give it the same priority as diet and exercise for a long and healthy life,” said Alberto Ramos, MD, MSPH, associate professor of neurology, and research director, Sleep Disorders Program University of Miami, Miller School of Medicine. 

Ramos was the senior author of a new study, “Actigraphic Sleep Patterns and Cognitive Decline in the Hispanic Community Health Study/Study of Latinos,” published December 22 in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association. 
Christian Agudelo, MD, clinical instructor, and Evelyn F. McKnight Neurocognitive Scholar, Division of Sleep Medicine in the Department of Neurology, was first author of the study, and Miller School coauthors were Douglas M. Wallace, MD, associate professor of neurology; and Sonja Kaur, MD, instructor of neurology. Researchers from eight other institutions participated in the study. 

“We found that longer  it takes to fall asleep, the greater the cognitive decline, perhaps because these individuals had shorter periods of deep sleep,” said Agudelo. “However, all of the study participants were leading normal lives without signs of cognitive impairments.” 

Another findings were that longer sleep durations were also associated with a decline in cognitive function, while taking naps was associated with less decline in memory function. “Our study accounted for important sleep variables, such as sleep apnea, insomnia, and daytime sleepiness, as well as behavioral and medical issues, such as obesity,” said Agudelo. 

The researchers used actigraphy (a wristband monitor) to analyze at-home sleep patterns for 1,035 adults, 45 to 64 years of age, from the Hispanic Community Health Study/Study of Latinos with participants from New York, Chicago and San Diego as well as Miami. Their cognitive functions from seven years ago was compared with current measurements.  

Ramos noted the importance of the long-term or longitudinal study of Hispanic adults. “Some studies indicate that Hispanics may have two to four times the risk of dementia, compared with non-Hispanic Whites,” he said. “If we can identify a marker, such as sleep latency, it may be possible to intervene to reduce the risk of cognitive decline in Hispanics and potentially other population groups.” 

Agudelo emphasized the importance of understanding how sleep affects health in all ages, genders and ethnicities. “Physicians need to be aware of sleep difficulties in the patients and suggest strategies for improvement,” he said. “For instance, going to sleep and waking up at the same times every day can lead to regular sleeping patterns.” 

While the new study indicated a correlation between sleep and cognitive decline, it did not attempt to determine causation. “Because the participants were under age 65, most likely the sleep changes preceded the cognitive changes, but more research will be needed to answer that question,” said Ramos. “Sleep is an important topic in this field, as more than 50 million people worldwide have cognitive decline and dementia, and the annual global economic burden of disease exceeds more than $1 trillion.”