Sleep is a continuous state that varies highly from minute to minute. Sleep is made up of two ‘types’ of stages: REM and non-REM, both characterized by differences in EEG. Non-REM includes stages 1, 2 and 3, with non-REM 3 (Slow Wave Sleep) being the deepest. Sounds simple enough. But, in addition, within these sleep stages, there are ‘micro’ markers of sleep, including sleep spindles. Sleep spindles occur mainly during non-REM2, and they look like small spools within the EEG. Among other things, sleep spindles are thought to be a marker of brain plasticity. Increased sleep spindle density (number of spindles per minute) has been linked with increased learning ability and increased intelligence. What’s more, boosting sleep spindle density seems to improve memory formation. So, put simply, the more spindles, the better.
So do those with untreated sleep apnea (i.e., disturbed sleep) still have sleep spindles? They sure do, but it has been suggested that those with untreated apnea have a reduced density of sleep spindles. If this were so, might CPAP (the gold standard sleep apnea treatment) reverse this reduction? This question was tested recently by a group of researchers at the JFK Neuroscience Institute in New Jersey, USA.
To perform this test, a group of individuals with untreated severe sleep apnea were prescribed to CPAP. The sleep spindle density of non-REM2 was tested before and after CPAP titration, and these values were compared. It was found that sleep spindle density increased significantly following titration. Spindle density was 5.5 spindles per minute before treatment, and 8.2 following treatment.
These findings are quite amazing given that sleep spindles are beneficial for brain functioning. This study showed that treating sleep apnea by applying CPAP restored sleep to a healthier level and thus boosted the cognitive benefits of sleep. Over time, improved cognition can contribute to fending off age-related cognitive decline. Therefore, each night of sleep apnea treatment can improve long-term cognition. Take home point: get treated and stay treated!
Source: Chokroverty, S., Bhat, S., Donnelly, D., Gupta, D., Rubinstein, M., & DeBari, V. A. (2015). Sleep spindle density increases after continuous positive airway pressure titration in severe obstructive sleep apnea: a preliminary study. Sleep Medicine.