Brain Fog After Poor Sleep: Too Little Oxygen Or Too Much Cortisol?

Ever have one of “those” days after a night of poor sleep? Your memory doesn’t seem to be at its best and your thoughts are sluggish. It has been demonstrated that sleep deprivation strongly impairs memory and learning, but the actual mechanism causing these deficits has not been definitively identified. Now, a study from the University of California, San Diego done on persons with sleep apnea may provide some much-needed answers as to why.

The researchers 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.

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 and is intimately involved in acquiring information and consolidating that information into long-term memory. This is important because it may explain why sleep-deprived individuals frequently exhibit poor memory and concentration abilities.

We know that people who have insomnia and those who chronically get inadequate sleep because of personal lifestyle choices have elevated levels of the stress hormone cortisol. These people do not have sleep apnea or low nighttime oxygen levels, yet they frequently exhibit cognitive dysfunction similar to patients with sleep apnea, so the common link may be the cortisol. We know that overstimulation of the adrenal gland produces the excess cortisol and the common thread is stress, produced by either insufficient sleep, or in the case of sleep apnea, fragmented sleep. Therefore, reducing cortisol output would be the base strategy to improving sleep quality and subsequent brain function.

First, adequate attention should be paid to maintaining a proper sleep environment. Keeping the room as dark as possible, noise- and distraction-free, and typically not warmer than 69 degrees will help promote proper rest. Avoiding stimulants such as caffeine, alcohol and high sugar foods, as well as television and other bright visual stimuli, prior to bedtime will also keep the body in a more relaxed state. (However, eating a healthy snack with some protein and fats 2-3 hours before bedtime will help keep the body from going into a hypoglycemic state overnight that triggers a release of cortisol.) Finally, find a way to mentally wind down before going to bed. Clear your mind of all the issues for tomorrow that you can’t do anything about tonight (except cause yourself more stress and poor sleep!). Take a hot, relaxing shower or bath, meditate or enjoy some quality family time. Take the steps to set yourself up for lower stress and a good night’s sleep, including planning enough time to actually sleep, and see if your mental function doesn’t improve as a result.

In Health, 

Dr. Brad Niewierowski