Poor Sleep Quality Linked to Cortical Atrophy

Pauline Anderson

September 03, 2014

Poor sleep quality is associated with brain atrophy over time, a new study shows. The relationship increases with age but isn't explained by variations in physical activity, body mass index (BMI), or blood pressure, researchers conclude.

To date, most research in this area has been on people with insomnia and has looked at brain volume at only 1 time point. This new study differed in that it included people with no pre-existing sleep problems and looked at change in brain volume over time as well as in cross-sectional analyses.

"We found that there was a greater decline associated with poor sleep over quite widespread brain regions," lead study author Claire Sexton, DPhil, postdoctoral research assistant, Department of Psychiatry, University of Oxford, United Kingdom, told Medscape Medical News.

The study is published online September 3 in Neurology.

Dr. Claire Sexton

Sleep Quality

The study sample included 147 persons aged 20 to 84 years who were participating in the ongoing Cognition and Plasticity through the Lifespan project at the University of Oslo, Norway. These participants underwent MRI at baseline between 2006 and 2009 and again between 2011 and 2012.

The participants' sleep quality was assessed between 2012 and 2013 by using the self-administered Pittsburgh Sleep Quality Inventory (PSQI), which has a possible score of 0 to 21. Using responses to the PSQI, researchers derived measures of sleep latency (minutes taken to fall asleep at night), sleep duration, and sleep efficiency (percentage of time in bed spent asleep).

The study showed that 35% of participants met PSQI criteria for "poor sleep." The average PSQI score among these participants was 8.5.

Researchers also assessed physical activity, BMI, and blood pressure, all of which have been associated with sleep quality, reduced gray matter volume, and atrophy.

In cross-sectional analyses, poor sleep quality was associated with smaller brain volume in a single cluster located within the right superior frontal cortex. Hippocampal volume was not associated with sleep quality.

The cluster remained significant in analyses that excluded outliers. There were significant correlations in both those under and those over age 60 years. Results were unchanged when physical activity, BMI, and blood pressure were included as additional covariates.

Smaller volume within this cluster was significantly associated with shorter sleep duration, lower sleep efficiency, and increased sleep latency.

Longitudinal analyses showed that poor sleep quality was associated with a greater rate of brain atrophy across the frontal, temporal, and parietal cortices. Although this study didn't correlate these anatomic findings with cognitive measures, other research has linked them to reduced measures of memory and poorer performance in various cognitive tests.

"That's something that needs to be explored in more detail in future," said Dr. Sexton. A "key" study would recruit people with insomnia, give them some sort of sleep therapy, and then, once their sleep has improved, see whether their cognitive performance has improved and their brain structure has changed, she said.

The current analysis comparing the PSQI-atrophy relationship found it to be stronger in older adults, possibly partly because this segment of the population experiences more sleep problems, said Dr. Sexton. She noted that up to half of older adults report poor sleep. "It's thought that a fair proportion of this is driven by people having physical health problems or mental health illness or problems with depression or pain."

The study found that while the overall sleep quality — including measures of duration, latency, and efficiency — was associated with MRI findings, sleep efficiency "was most linked to brain volume," said Dr. Sexton. However, other research has found a stronger tie with sleep duration. "So there are mixed reports," said Dr. Sexton.

It could be that poor sleep is causing the brain to atrophy, that having good-quality sleep restores and repairs the brain. "This is the angle I'm looking to concentrate in future research," said Dr. Sexton. "If we can improve people's sleep, then this could be an important way to help slow decline in brain volumes and improve brain health."

It's a "really exciting avenue" of research, she added. "There are a lot of successful treatments for insomnia, including such things as improving sleep hygiene and getting into better sleep habits, that can help improve sleep efficiency."

However, the relationship between sleep and brain volume is likely at least somewhat bidirectional: Atrophy may lead to poor sleep as well as the other way around. It's also possible that a third factor causes both poor sleep quality and brain atrophy. Although physical activity, BMI, and blood pressure were not associated with sleep quality in this study, the sample size may have been too small, she noted.

A limitation of the study was that it didn't investigate the underlying cause of high PSQI scores. However, study participants were screened for neurologic and psychiatric illness.

In addition, sleep quality was assessed an average of 1.3 years after the second neuroimaging assessment, which may have "added noise to our analyses," the authors write.

Important Implications

Asked to comment on these findings, Judy Willis, MD, a neurologist with an interest in memory and sleep based in Santa Barbara, California, and a member of the American Academy of Neurology, said the study supports and extends previous findings linking poor sleep quality with atrophy in a region of the right superior frontal cortex.

Noteworthy about this study, said Dr. Willis, is that in participants over age 60, a significant increase in the proportional change in cortical volume was associated with reduced sleep efficiency. As well, she said, the differences in sleep quality couldn't be explained by changes in physical activity, BMI, or blood pressure.

These new results, said Dr. Willis, have important implications for future research. "As we continue to search for causes of Alzheimer's disease and other types of cognitive decline, as well as for exacerbating factors, comorbidities, and interventions to reduce risk and severity of these conditions, further assessments are needed to evaluate if poor sleep quality may be a cause or a consequence of brain atrophy," she told Medscape Medical News.

Dr. Willis agreed with the authors that the associations uncovered by the study between the rate of atrophy and disorders of sleep quality should promote further longitudinal investigations. "While further studies continue to evaluate causation, investigations also should go forward to evaluate the impact that treatment of sleep quality disorders has on both the rates of atrophy and the degree of cognitive decline."

The study was supported by the Research Council of Norway, the United Kingdom National Institute for Health Research, Wellcome Trust, Norwegian Research Council, European Research Council, and University of Oslo. Dr. Sexton has disclosed no relevant financial relationships.

 Neurology. Published online September 3, 2014. Abstract

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