Sleep apnea and brain injury raise risk of later dementia

August, 2011

Recent studies add to the evidence that sleep apnea and even mild brain injury increase the risk of developing dementia.

Sleep apnea linked to later dementia

A study involving 298 older women with sleep problems found that those who had disordered breathing (such as sleep apnea) were significantly more likely to develop dementia or mild cognitive impairment.

Around a third of the women (average age 82) had disordered breathing (slowing down or stopping breathing during sleep and often having to gasp to catch up). None showed signs of cognitive impairment at the time of the sleep testing. When re-tested some five years later, 45% of those who had disordered breathing had developed dementia or MCI, compared with 31% of those with no breathing irregularities.

Those whose sleep irregularities had been particularly severe (15 or more breathing stoppages per hour and more than 7% of sleep time not breathing) during the earlier part of the study were nearly twice as likely as those without breathing problems to develop dementia or MCI. Other measures of sleep quality — waking after sleep onset, sleep fragmentation, sleep duration — were not associated with cognitive impairment.

The finding adds to the evidence for the importance of treating sleep apnea. Previous research has found that CPAP treatment effectively counteracts cognitive impairment caused by sleep apnea.

Brain injury raises dementia risk

Analysis of medical records on 281,540 U.S. military veterans aged at least 55 at the beginning of the study has found that over the next seven years those who had at one time suffered a traumatic brain injury were more than twice as likely to develop dementia than those who had not suffered such an injury. Around 1.7% (4,902) had incurred a traumatic brain injury, in many cases during the Vietnam War, and over 15% of these developed dementia. In contradiction of the prevailing belief that only moderate or severe brain injuries predispose people to dementia, severity of the injury made no difference.

Injuries due to strokes were weeded out of the study.

In another study, following up on nearly 4,000 retired National Football League players surveyed in 2001, 35% appeared to have significant cognitive problems (as assessed by questionnaire). When 41 of them were tested, they were found to have mild cognitive impairment that resembled a comparison group of much older patients from the general population.

The findings are a reminder of the importance of treating even mild head injuries, and of following a regime designed to mitigate damage: exercising, eating a healthy diet, reducing stress, and so on.

Reference: 

[2444] Yaffe, K., Laffan A. M., Harrison S L., Redline S., Spira A. P., Ensrud K. E., et al.
(2011).  Sleep-Disordered Breathing, Hypoxia, and Risk of Mild Cognitive Impairment and Dementia in Older Women.
JAMA: The Journal of the American Medical Association. 306(6), 613 - 619.

The brain injury studies were reported in July at the Alzheimer's Association International Conference in France. http://www.alz.org/aaic/

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