New research suggests that sleep apnea and reduced deep sleep are associated with the development of brain biomarkers linked to an increased risk of stroke, Alzheimer's disease, and cognitive decline. While the study does not establish a causal relationship between sleep disturbances and brain changes, it highlights an important connection. The findings have been published in the journal Neurology.
The study focused on sleep factors and biomarkers that assess the health of the brain's white matter, which plays a crucial role in connecting different brain regions. One of the biomarkers, called white matter hyperintensities, refers to small lesions visible on brain scans. These hyperintensities become more prevalent with age or uncontrolled high blood pressure. The other biomarker evaluates the integrity of axons, which are nerve fibers responsible for connecting nerve cells.
Diego Z. Carvalho, a member of the American Academy of Neurology and study author from the Mayo Clinic in Rochester, Minnesota, explained that these biomarkers are indicative of early cerebrovascular disease. The study revealed that severe sleep apnea and a decrease in slow-wave sleep were associated with these biomarkers. Carvalho emphasized the significance of these findings, given the absence of treatment options for such brain changes. He stressed the need to prevent or mitigate their progression.
The research involved 140 participants, aged on average 73, with obstructive sleep apnea. The participants underwent brain scans and overnight sleep studies in a laboratory. None of the participants had cognitive issues at the beginning of the study, nor did they develop dementia during the study period. The severity of sleep apnea varied among the participants, with 34% experiencing mild cases, 32% moderate cases, and 34% severe cases.
The sleep study measured the time individuals spent in slow-wave sleep, also known as non-REM stage 3 or deep sleep, which is considered a reliable indicator of sleep quality. The researchers discovered that for every 10% decrease in the percentage of slow-wave sleep, there was an increase in the presence of white matter hyperintensities equivalent to aging by 2.3 years. The same decrease was also associated with reduced axonal integrity, comparable to aging by three years.
Participants with severe sleep apnea exhibited a higher volume of white matter hyperintensities compared to those with mild or moderate sleep apnea. Additionally, their brains showed reduced axonal integrity. Carvalho emphasized the need for further research to determine whether sleep issues influence these brain biomarkers or if the relationship works the other way around. The study also calls for investigations into whether improving sleep quality or treating sleep apnea can impact the progression of these biomarkers.
In summary, the study highlights the association between sleep apnea, reduced deep sleep, and the development of brain biomarkers associated with stroke, Alzheimer's disease, and cognitive decline. While the causal relationship is yet to be established, the findings underscore the importance of addressing sleep disturbances and their potential impact on brain health. Further research is necessary to explore the interplay between sleep issues and brain biomarkers and to evaluate potential interventions to prevent or mitigate these changes.