From Medscape Medical NewsPTSD Linked to a Near Doubling of Dementia Risk in Veterans
June 16, 2010 — In the first study to suggest PTSD may be an independent risk factor for dementia, the disorder, which reportedly affects 17% of veterans returning from the current conflicts in Iraq and Afghanistan, was associated with a 2-fold increased risk for incident dementia in older veterans.
A large, retrospective cohort study that was initially presented at the International Conference of Alzheimer's Disease in July 2009, and reported by Medscape Psychiatry at that time, the study shows that during 7 years of follow-up, veterans with PTSD had almost a 2-fold increased risk of developing dementia compared with their PTSD-free counterparts. This association remained after adjusting for differences between the 2 groups, including demographics and medical and neuropsychiatric comorbidities.
According to investigators led by Kristine Jaffe, MD, from the University of California–San Francisco and San Francisco Veterans Affairs Medical Center, this research is "the first, to our knowledge, to report that PTSD may increase the risk of developing dementia."
The study appears in the June issue of the Archives of General Psychiatry.
According to investigators, it has been estimated that the prevalence of PTSD is 17% among veterans returning from the current conflicts in Iraq and Afghanistan. Previous research has shown that PTSD may impair cognition and that older individuals with PTSD experience a greater decline in cognitive performance relative to healthy control patients. However, little is known about PTSD as a potential risk factor for dementia.
To examine this issue, researchers analyzed data from 181,093 veterans aged 55 years or older without dementia from 1997 through 2000. Of these individuals, 53,155 had a diagnosis of PTSD and 127,938 did not.
The study's primary outcome measure was incident dementia during a 7-year follow-up period between October 1, 2000, and December 31, 2007.
The investigators found that veterans with PTSD had a 7-year cumulative incident dementia rate of 10.6% vs 6.6% in those without the disorder (P < .001). Unadjusted analyses revealed that patients with PTSD were more than twice as likely to develop incident dementia compared with those without PTSD (hazard ratio, 2.31; 95% confidence interval, 2.24 - 2.39).
After adjustment for demographics and medical and neuropsychiatric comorbidities, the study showed that veterans with PTSD were still more likely to develop dementia (hazard ratio, 1.77; 95% confidence interval, 1.70 - 1.85).
In addition, the researchers report that the study results were similar when they excluded patients with a history of head injury, substance abuse, or clinical depression.
According to the authors, there are several reasons why patients with PTSD may have an increased risk of developing dementia. PTSD may contribute to the cause of dementia, or chronic stress may link the 2 conditions. Stress may damage the hippocampus or cause alterations in neurotransmitter and hormone levels that could precipitate dementia.
"The finding that PTSD is associated with a near doubling of the risk of dementia has important public health, policy and biological implications," the authors write. "It is important that those with PTSD are treated, and further investigation is needed to see whether successful treatment of PTSD may reduce the risk of adverse health outcomes including dementia.
"In addition, it is critical to follow-up patients with PTSD, especially if they are of an advanced age to screen for cognitive impairment. Finally, mechanisms linking PTSD and dementia must be identified in hope of finding ways to improve the care and outcomes of patients with PTSD," the investigators write.
Commenting on the study for Medscape Psychiatry, Maria C. Carrillo, PhD, senior director, Medical and Scientific Relations, for the Alzheimer's Association, said this was "an extremely interesting" study that was highlighted at the International Conference of Alzheimer's Disease last year.
"As an association we are always trying to elucidate risk factors and understand how they interact with each other to increase Alzheimer's and dementia risk. We certainly recognize that that this was a great group of researchers, a great study, and certainly it had powerful numbers in terms of statistical significance," Dr. Carrillo said.
Dr. Carrillo added that the findings are particularly sobering in light of the fact that there will be a large number of returning veterans — many of whom will have PTSD — during the next 2 years.
"This means we're facing another large bolus of people with an increased risk of dementia over the next few decades, added to what we're already expecting in terms of the Baby Boomer population — the first wave of which will turn 65 [years old] in 2011," she said.
Dr. Carrillo said the finding that PTSD and dementia are linked was not entirely surprising "We already know that traumatic brain injury and certainly chronic stress increase the risk of cognitive decline and what this paper refers to as 'accelerated aging,' which may in turn lead to early dementia. So it makes sense that PTSD would increase the risk for dementia in the long run," said Dr. Carrillo.
Although further prospective research is warranted, on the basis of these findings it is important for the public and clinicians to understand that PTSD may elevate dementia risk, so the condition can be treated with a view to improving outcomes, including possibly reducing dementia risk, she added.
/The study was supported by the Military Operational Medicine Research Area Directorate, US Army Medical Research and Material Command, Fort Detrick, Maryland. Dr. Yaffe reports having served as a consultant to Novartis Inc. Dr. Vittinghoff reports having received grant support from Zelos Therapeutics, Tethys Bioscience Inc, and NPS Pharmaceuticals. Dr. Neylan reports having served as a consultant for Actelion Pharmaceuticals Ltd and Takeda Pharmaceutical Company Limited and receiving lecture fees from speaking at the invitation of the Chatham Institute and the Pri-Med Institute. Dr. Marmar reports having served as a consultant for Sanofi Aventis LLC and Actelion Pharmaceuticals Ltd.
Arch Gen Psychiatry. 2010;67:608-613. Abstract
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