By Robert Rosenberg, DO
You know how your brain acts when you’re tired: it’s hard to remember things and your thoughts are sluggish. Sleep deprivation strongly impairs memory and learning, and research confirms this (though the actual mechanism causing these deficits has escaped detection). However, a recent study done on persons with sleep apnea may provides some much-needed answers as to why.
The researchers, from the University of California, San Diego, checked 55 sleep apnea patients’ blood cortisol levels every two hours for 24 hours. The patients underwent sleep studies the following night and then took a battery of tests to assess cognitive function. The researchers looked to see how many times they stopped breathing, and how often their oxygen levels dropped in response to airway obstruction.
Previous research has assumed that sleep-related memory problems are caused by a drop in oxygen. But this study found that it was elevated cortisol levels that best predicted cognitive dysfunction.
The results are in line with previous studies that have demonstrated chronic exposure to elevated cortisol levels can result in impaired cognitive function. In fact, prior studies have revealed adverse effects of elevated cortisol on the brain’s hippocampus. The hippocampus is a structure that resides in the temporal lobe of the brain. It is intimately involved in acquiring information and consolidating that information into long-term memory.
Why is this important? It may explain why sleep-deprived individuals frequently exhibit poor memory and concentration abilities. We know that insomnia sufferers, and those who chronically get inadequate sleep because of life style choices, have elevated levels of stress hormones such as cortisol. These folks do not have sleep apnea or low nighttime oxygen levels, yet they frequently exhibit cognitive dysfunction similar to patients with sleep apnea. Perhaps what they have in common is elevated levels of the hormone cortisol.
It is plausible that overstimulation of the adrenal gland produces the excess cortisol. The common thread is stress, produced by either insufficient sleep, or in the case of sleep apnea, fragmented sleep. Measuring cortisol levels in patients with sleep apnea and insufficient sleep may provide an important diagnostic tool. I am hopeful that this might serve as a motivator to convince people of the importance of good quality sleep. If it worked, a simple lab test may convince people to take their sleep and sleep disorders seriously. I am aware that much of this is still speculative. However, if future studies related to sleep continue to demonstrate this relationship, the possibilities are exciting.
http://www.everydayhealth.com/columns/robert-rosenberg-sleep...
