In a study of Gulf War veterans, disrupted sleep patterns were associated with a lower brain volume, suggesting that effective treatment for insomnia might improve some cognitive functioning.
"People discount the importance of sleep [to cognitive functioning],” researcher Linda L. Chao told Reuters. “So many things seem so much more important than a few extra hours of sleep a night. The study suggests we shouldn't discount sleep importance.” Chao, a scientist with the University of California at San Francisco, published a study this week in the journal Sleep after collaborating with researchers from the Department of Veterans Affairs.
While past work has linked sleep problems to brain changes, researchers in this study observed changes in the amount of grey matter — or “brains” — found in the frontal lobe, says psychiatrist John Winkelman, a sleep expert at Massachusetts General Hospital in Boston. "There's other corroborating data showing that insomnia and a variety of psychiatric illnesses are reflected in reduced volumes in the brain, which makes sense because sleep and mood are functions of the brain," he told Reuters.
The brain’s frontal lobes, he said, were “an essential part of human functioning” necessary for maintaining the continuous phenomenon we refer to as the self — that which plans and ponders, an emotive area also important to mood and affect.
Chao and her co-investigators initiated the study of Gulf War veterans to learn more about how post-traumatic stress disorder, also known as PTSD, may affect sleep patterns. Previous work has shown high rates of sleep disorders among U.S. military veterans returned from war in Iraq and Afghanistan, the latter of which still continues in a prolonged period of denoument.
In this investigation, Chao used functional-magnetic resonance imaging to scan the brains of 144 veterans, most of whom were men. The veterans rated their sleep health using the Pittsburgh Sleep Quality Index, a simple inventory covering sleep patterns over the past month. After comparing the self-reports with brain scans, Chao found that veterans with sleep problems had less grey matter in the frontal lobe than others. Although half abused alcohol and some 40 percent had experienced major depression disorder, the link between sleep problems and lowered brain volume appeared pretty tight, in the after-analysis, which also considered the effects of prescription medication, among others.
Other scientists hesitated to say whether disrupted sleep caused any loss of grey matter, however. Further investigation is needed, Chao agreed.
Source: Chao, Linda L., Mohlenhoff, Brian S., Weiner, Michael W., Neylan, Thomas. Sleep. 2014.