Measuring Sleep Duration and Identifying Phenotypes Linked to Cognitive Decline in Hispanic Populations

Alberto Ramos, MD, FAAN

(Credit: LinkedIn)

Sleep problems have long been linked in prior studies to cognitive difficulties, including subjective cognitive decline, which often precedes measurable changes and dementia. In recent years, phenotype-based approaches have gained traction in sleep research because of the heterogeneous presentation of sleep symptoms. Although some research has connected sleep phenotypes to vascular risk factors, less is known about their relationship with subjective cognitive decline. Recently, researchers conducted an investigation in a large, diverse cohort of Hispanic/Latino individuals to further explore this connection.¹

Studies also have shown that sleep can play a critical role in brain health for aging adults and may offer opportunities to prevent or slow cognitive decline. Research from the Hispanic Community Health Study/Study of Latinos previously showed an association between sleep duration, particularly long sleep, and neurocognitive decline over a 7-year period. Questions remained about whether these associations persisted over longer timeframes or are influenced by sleep apnea, which can lead to both short and long sleep durations. Thus, recent studies assessed baseline sleep duration in relation to cognitive trajectories over 14 years and the potential effects of sleep apnea severity.²

Sleep expert Alberto Ramos, MD, FAAN, director of the Sleep Disorders Program at the University of Miami, presented both of these studies related to sleep and cognitive health at the recently concluded 2025 Alzheimer’s Association International Conference, held July 27-30, in Toronto, Canada. In an interview with NeurologyLive^® following the conference, Ramos discussed how different aspects of sleep may influence cognitive function over time based of the findings from the presented studies. He noted that the results highlight potential links between sleep patterns and perceptions of cognitive decline, suggesting that certain sleep characteristics could serve as early indicators or targets for interventions to support cognitive health.

NeurologyLive: Provide an overview of the research you presented at AAIC, why was it a focus for you?

Alberto Ramos, MD, FAAN: We had 2 posters based on the analysis we did from the Hispanic Community Health Study, or Study of Latinos, which is an ongoing cohort study that has been around for more than 15 years now. We have looked at how different sleep measures over time contribute to cognitive decline, cognitive impairment, or mild cognitive impairment. Hopefully, now that the cohort is getting a little bit older, we’ll be able to determine how sleep issues may contribute to dementia risk, whether Alzheimer or other types of dementia.

What was the significance surrounding your first poster and the link between sleep duration and cognitive decline?

In these studies, the first poster we presented was about the self-report of sleep duration at baseline—which happened between 2008 and 2011—and how it associates with cognitive trajectories or decline over 14 years. We have 3 different time points. The first 1 coincided with the first assessment of sleep, and then we had 2 other time points. Now, it’s up to about 14 or 15 years that we have been able to obtain sleep measures.

We see that those people who, at baseline—meaning at the beginning of the study—said they slept more than 9 hours had worsening cognition over time, with declining trajectories across general cognition, memory, and executive function after 14 years, compared with those who slept anywhere from 7 to 9 hours. There was no effect among those who slept less than 7 hours, the shorter sleepers. So, people who, at least at the beginning of the study, stayed in bed or slept for long periods seemed to have their cognition decline over time. That’s the first poster we presented.

What did you find about sleep phenotypes and their link to self-reported cognitive decline in your second poster?

The other poster looked at different phenotypes—meaning different presentations—of sleep issues and how they are associated with self-reported cognitive decline. This was more or less in a subpopulation of the Hispanic study participants who are undergoing ongoing cognitive testing and sleep testing. We were able to determine 3 different phenotypes using what is called cluster analysis, which is a fancy way to single out the different presentations of sleep issues across the population.

We saw that there are 3 different phenotypes, consistent with other studies—not only in our population—of people who have more daytime sleepiness (more tired or sleepy throughout the day), people with more insomnia-like symptoms or more fragmented sleep, and people who are minimally symptomatic, meaning they don’t endorse many symptoms. We looked at how those 3 phenotypes mapped to self-reported cognitive decline.

This other metric measures how people perceive their cognitive issues to have progressed over the last 10 years. They’re asked questions like, “Over the last 10 years, is my memory good or bad? Is my thinking speed good or bad?” Through different components, we were able to see how people think their cognition has changed over the last 10 years—whether it has declined or stayed the same.

Why are your findings on sleep issues and cognitive decline clinically important, and how might they inform early intervention?

That’s important because a lot of studies have shown that people with self-reported cognitive decline are the ones who actually go to cognitive clinics more often to say, “Hey, I don’t think the same as 10 years ago, 5 years ago,” or whatever it might be. This also seems to represent a potential presymptomatic stage before they start to perform poorly on objective cognitive testing. At the beginning, people with subjective cognitive decline may still test well, but over time they seem to decline faster on objective testing.

We saw that those people who had more daytime sleepiness and insomnia symptoms in the cluster we defined had more subjective cognitive decline. These things were quite interrelated. Of course, it’s hard to tell exactly if the subjective cognitive decline precedes the sleep issues, or vice versa. However, at least temporally wise, we measured sleep first, and then the self-reported cognitive decline later. So it seems that if you have sleep issues now, when we measure self-reported cognitive decline later, that could potentially be a predictor—or at least show a strong association—with not having the same memory function or processing speed afterward.

We were able to see that sleep issues—in 2 different papers but under the same hypothesis—predict both self-reported cognitive decline and objective cognitive decline after 15 years. This could potentially be a very early warning sign of developing dementia in the near future. More importantly, it’s something that we can treat or target as a preventive measure.

Transcript edited for clarity. Click here for more coverage of AAIC 2025.

REFERENCES
1. Ramos AR, Tarraf W, Decarli C, et al. Sleep duration predicts 14-year cognitive decline: A preliminary analysis of the Hispanic Community Health Study/Study of Latinos. Presented at: 2025 Alzheimer’s Association International Conference; July 27-31; Toronto, Canada. Abstract 105332.
2. Gonzalez KA, Membreno R, Tarraf W, et al. Sleep phenotypes and self-reported cognitive decline in the Hispanic Community Health Study/Study of Latinos. Presented at: 2025 Alzheimer’s Association International Conference; July 27-31; Toronto, Canada. Abstract 104449.