New Study Links Sleep Disorders to Dementia
New findings presented at the 2014 Alzheimer’s Association International Conference revealed a link between disturbed sleep and dementia. The results came from a team of researchers at UC San Francisco.
Led by principal investigator Kristine Yaffe, M.D., the UC San Francisco team examined the medical records of 192,266 Armed Forces veterans over the age of 55. The medical record data was randomly selected from the Department of Veterans Affairs National Patient Care Database. Since the vast majority of current U.S. Armed Forces veterans are male, the majority of the randomly selected subjects for this study were also male. None of the subjects were suffering from dementia at the start of the study.
Previous research has found that sleep latency (trouble falling asleep), sleep fragmentation (frequently waking up), lower levels of REM sleep and sleep disorders all become more common as humans get older. Some prior research also suggests that veterans as a whole experience a higher rate of sleep disturbance than non-veterans.
No Dementia Present at Baseline
The researchers first established a baseline from the time medical records were chosen for the study between 2002 and 2003. At this baseline, 7.5 percent of the subjects were suffering from some kind of sleep disturbance, such as sleep apnea or insomnia.
Between 2004 and 2011, the UCSF researchers followed up with each patient’s records in order to discover the incidence of dementia. They found that 10.6 percent of the veterans who had problems with sleep disturbance at the baseline had subsequently developed dementia. In contrast, 9 percent of the veterans without sleep disturbance had developed dementia.
The team’s final calculations, after accounting for demographics and comorbid conditions, showed an increased dementia risk of 30 percent for veterans with sleep disturbances compared to veterans without sleep disturbances. The results specifically for sleep apnea and insomnia were similar: a 33 percent increased risk for the former, and a 27 percent increased risk for the latter.
So far, the researchers can only speculate about the physiological mechanisms behind this higher risk of dementia. According to Dr. Yaffe, some animal research has suggested a link between hypoxia (disrupted oxygen flow) in the brain from sleep disturbances and amyloid deposition, which has been connected to dementia.
With PTSD, Risk Skyrockets
The new study also showed that the additional presence of post-traumatic stress disorder (PTSD) in veterans with disrupted sleep patterns increased the risk of dementia from 30 percent to a very disturbing 80 percent. PTSD is found in veterans of the Armed Forces at much higher rates than in the general population. The combination of higher rates of sleep disturbances and higher rates of PTSD among the veteran population suggests that veterans overall may face a much greater risk of developing dementia.
Dr. Yaffe believes that this information could be put to effective use in efforts to prevent dementia in this and other vulnerable populations. Some sleep disturbances are easy to treat, but studies have found that a large number of them are never diagnosed. If older patients could be more aggressively screened and treated for sleep disturbances, it could have a significant impact on the number of people who suffer from dementia later in life.
It also provides yet another strong incentive to identify and treat PTSD in veterans and the general population. This illness can involve frustratingly painful and even debilitating symptoms such as traumatic flashbacks, memory problems, extreme outbursts of anger, emotional numbness and extreme tension or nervousness. The threat of dementia in addition to these and other symptoms only adds to the urgent need for treatment.