Jan. 20, 2011 -- Adults with symptoms of ADHD, or attention deficit hyperactivity disorder, are more than three times as likely as other adults to develop a form of dementia later in life, according to new research from Argentina.
''We found a higher risk of dementia with Lewy bodies in patients with preceding adult ADHD symptoms," write the researchers from Hospital Italiano Buenos Aires. The study is published in the European Journal of Neurology.
Lewy body dementia (LBD) affects about 1.3 million people in the U.S., according to the Lewy Body Dementia Association. Lewy bodies is the name given to the abnormal protein deposits that disrupt the brain's normal functioning.
The symptoms include cognitive impairment, like the more well-known dementia, Alzheimer's disease. However, in the Lewy body form, patients can also have visual hallucinations, fluctuation in cognition -- sometimes appearing fine, other times not -- and motor abnormalities similar to those in Parkinson's disease patients.
But a U.S.-based expert cautions that the study found an association between ADHD symptoms and the dementia, not cause and effect. "It may be that both of these disorders are linked to some other risk factor that is common for both," says James B. Leverenz, MD, chair of the Lewy Body Dementia Association's scientific advisory council and professor of neurology and psychiatry and behavioral sciences at the University of Washington, Seattle. He reviewed the study for WebMD.
ADHD and Dementia: The Study
Led by Angel Golimstok at the Hospital Italiano Buenos Aires, researchers evaluated 360 patients with dementia -- 109 had LBD and 251 had Alzheimer's -- comparing them with 149 healthy people matched by sex, education, and age.
Then they looked at how often ADHD symptoms had been reported earlier. In patients who were too impaired to answer, they got information from an informant who had known the patient for at least 10 years and had information from a close relative who knew the patient in childhood. The researchers say that since this method has not been validated, they refer to the patients as having ADHD symptoms, rather than being diagnosed with ADHD.
- 47.8% of those with LBD had previous ADHD symptoms.
- 15.2% of those with Alzheimer's disease had previous ADHD symptoms.
- 15.1% of those in the healthy group did.
Why the link? "It is believed that the same neurotransmitter pathway problems are involved in the development of both conditions, so our research set out to test the theory that adult ADHD often precedes [Lewy body dementia],'' Golimstok says in a news release.
The researchers believe their study is the first to look at the link between ADHD symptoms and dementia.
In ADHD, often diagnosed in childhood, people have problems paying attention and can act impulsively. Symptoms can persist into adulthood.
“Our hypothesis is that ADHD could be the clinical result of the first step in these pathway disorders, and after a long time, this problem degenerates to a more severe pathology with structural changes in the brain, as Lewy Body Dementia is," Golimstok writes in an email interview with WebMD.
"A question to answer in the very near future is, Could available ADHD treatment prevent the conversion to a degenerative disease such as Lewy Body Dementia?" Golimstok writes.
ADHD and Dementia: Exploring the Link
Although the study doesn't prove cause and effect between ADHD and dementia, it is valuable, Leverenz says.
"The importance in this study ... is that we are trying to identify early symptoms and characteristics that may predict who is at high risk of developing this disease," he says of LBD.
That way, when a preventive treatment does become available, he says, ''We can help these people."
An ADHD expert who also reviewed the study for WebMD says the conclusion is backward. Instead of saying that people with ADHD symptoms are three times as likely to get LBD, the researchers should have concluded that "patients with LBD had three times the rate of ADHD symptoms," says L. Eugene Arnold, MD, professor emeritus of psychiatry at Ohio State University's Nisonger Center and a longtime ADHD researcher.
But Arnold says the link found is worth exploring and that the neurotransmitter problems thought to be involved in ADHD in fact may also be involved in the dementia.
Like other experts, Arnold says that retrospective studies are inherently flawed, as people must recall their histories or those of loved ones.
"The authors tried to obtain ratings of ADHD during childhood from knowledgeable informants of the patients and controls, and much hinges on the accuracy of these reports, and on their interpretation," says Douglas Galasko, MD, professor of neurosciences at the University of California San Diego, who also reviewed the study. He says the next step is replication of the findings by other researchers.
ADHD and Dementia: What to Do Now?
Meanwhile, is there anything an adult with ADHD might do to minimize later risk of dementia?
"I always tell people we don't know how to prevent this disease," Leverenz says of LBD. "However, we do know that people who maintain their general health -- the old boring stuff, exercise, proper diet -- they seem to be able to resist the effect of the disease better."
Arnold agrees. "Those two things will do a lot to prevent or delay most diseases."