Sleep apnea is characterized by breathing that repeatedly stops and starts, loud snoring, restless sleep, and sleepiness throughout the day. For some time, we have known that those with sleep apnea in mid-life are more likely to have Alzheimer's later on. Now, researchers have found neurological evidence for the link.
For their study, the researchers studied 34 postmortem samples from people who had obstructive sleep apnea. While none of the patients had received a dementia diagnosis, 70% had neurofibrillary tangles, and 38% had amyloid plaques on their hippocampi.
After adjusting factors such as age, body mass index, and sex, the researchers noticed that the severity of the condition correlated with reductions in volume in the hippocampus, a part of the brain key for memory that also reduces in volume in people with Alzheimer's. They also noticed that some had a density of plaques and tangles sufficient to qualify for Alzheimer's disease.
Adding to this, they found that each person's severity of sleep apnea correlated with how much amyloid plaque they had in their hippocampi. They found, however, that sleep apnea did not correlate with the number of neurofibrillary tangles in the hippocampi.
Nevertheless, in mild cases of sleep apnea, the researchers reported finding plaques and tangles only in a cortical area near the hippocampus- exactly where they first occur in Alzheimer's disease.
Explaining how this happens, the researchers suggested that repeated bouts of oxygen deprivation from sleep apnea may cause oxidative stress to build up amyloid plaques in the hippocampus. They say that this process may make these areas more vulnerable to Alzheimer's.
Although interesting findings, the researchers caution that their results come from a relatively small sample size, and that their study did not involve a control group. As such, further research is needed to confirm their validity.