While all of our brains get smaller as we get older, a startling new study shows that the amount of sleep we get -- or the lack thereof -- could affect how fast they shrink, particularly in people over 60 years old.
“We found that sleep difficulties (for example, trouble falling asleep, waking up during the night, or waking up too early) were associated with an increased rate of decline in brain volume over 3 [to] 5 years,” lead researcher Claire Sexton, DPhil, with the University of Oxford, wrote in an email to The Huffington Post. "Many factors have previously been linked with the rate of change in brain volume over time -- including physical activity, blood pressure and cholesterol levels. Our study indicates that sleep is also an important factor."
The study, published Wednesday in the journal Neurology, is an associative one, which means it doesn’t show whether sleep causes rapid brain shrinkage or if a rapidly shrinking brain results in poorer sleep. Still, Sexton said future research based on her findings could encourage people to take their sleep schedule more seriously.
"In [the] future, we would like to investigate whether improving sleep can help slow decline in brain volume," wrote Sexton. "If so, this could be an important way to improve brain health."
For the study, Sexton evaluated 147 adults between 20 and 84 years old. They all underwent two MRI brain scans an average of 3.5 years apart. They also answered a survey about their sleep quality.
Among the participants, 35 percent had poor sleep quality (which considers factors like how long it takes to fall asleep at night or sleeping pill use, among other things). Sexton found that their brain scans showed a more rapid decrease in the frontal, temporal and parietal parts of the brain.
The frontal lobe regulates decision-making, emotions and movement, while the parietal lobe is where letters and words combine into thoughts, according to the National Institutes of Health. Meanwhile, the temporal lobe is associated with memory and learning.
Sexton's research echoes other recent studies on sleep and the aging brain. A study from a group of scientists from Duke-NUS Graduate Medical School Singapore was published last July that found people who slept fewer hours had brains that aged faster than the controls (in this study, it was demonstrated with brain ventricle enlargement, which is a marker for cognitive decline). Another study, from Beth Israel Deaconess Medical Center in New York, found that the decline of a certain cluster of neurons was associated with higher rates of disrupted sleep in adults over 65. The effect was even more pronounced in study participants with Alzheimer's disease.
Louis Ptacek, M.D., a neurology professor and sleep expert at UC San Francisco, praised Sexton’s “reasonable” and “sound” study for controlling for factors like BMI and physical activity, which are known to affect sleep habits. But he also said the study’s findings, while interesting, are not surprising.
"We know, for example, that in many neurodegenerative diseases, you get all kinds of sleep problems,” Ptacek told HuffPost. "It’s not 100 percent uniform, but we know that Alzheimer’s patients, dementia patients and Parkinson’s patients all have different kinds of sleep phenotypes.”
It's not surprising that bad sleep is associated with decreased size or increased atrophy in different parts of the brain -- "in fact, I would have predicted that," Ptacek said. "But of course, these investigators did the study and proved it."
Ptacek hopes that as more research on the importance of sleep emerges, the public will begin to prioritize sleep seriously as another aspect of health, as opposed to thinking of it as an inconvenience or something to shortchange. We still have a long way to go, both in recognizing how vital sleep is to well-being and in funding more research on the mechanisms of sleep, he said.
“We all spend a third of our lives doing it, and yet, the understanding of the importance of good quality sleep to our health is sort of where tobacco and smoking was 40 years ago,” said Ptacek. " We know almost nothing about sleep at a basic mechanistic level: What is sleep really, and why do we do it?”
Even in 2014, "no one has any idea about the answers to these questions," he said.