ADHD triples dementia risk, found in first study
A common form of dementia has been linked to attention-deficit and hyperactivity disorder (ADHD).
The neurologic disorder that seems to be preceded by ADHD, found in the study is dementia with Lewy bodies (DLB). Researchers from Argentina were able to confirm their findings in a study of 360 patients with degenerative dementia and 149 healthy matched controls based on age, education and gender. The researchers believe the research is the first to link ADHD to later development of dementia.
In the dementia study group, 109 people had DLB and 251 had Alzheimer’s disease. The researchers found 48 percent of those with dementia with Lewy bodies had attention-deficit and hyperactivity disorder. According to lead author Dr Angel Golimstok, "This was more than three times the 15 per cent rate found in both the control group and the group with Alzheimer's.
ADHD is a common disorder in children and adolescents says Golimstok, and DLB accounts for about ten percent of dementias in older people.
Symptoms of DLB are progressive and disabling and include difficulty with physical skills, declines in mental capacity, movements similar to Parkinson’s disease and sometimes hallucinations. Symptoms of ADHD include hyperactivity, impulsivity and trouble with attention, according to information from the study.
According to Dr Golimstok, "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 DLB."
In the study, the patients were 74 and 75 years old on average for dementia with Lewy bodies and Alzheimer’s disease respectively. Criteria for the study included mild to moderate dementia, based on the mini mental status examination scale and one to two for clinical signs of dementia.
ADHD was assessed directly from the participants or informants. For those with cognitive impairment, reports were obtained from individuals who had known the subject for at least 10 years, had information from relatives and knew the participant during childhood.
To ensure assessments of ADHD, DLB and Alzheimer’s disease were correct, two neurologists, unaware of the study, also examined the study participants and were in agreement with the researchers findings in of 98 per cent in the DLB group, 96 per cent in the Alzheimer's group and 97.5 per cent in the control group.
The neurologists used the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) and Wender Utah Rating Scale tool that assesses ADHD. In cases of disagreement about ADHD, a third neurologist was asked to assess the study group. Attention-deficit and hyperactivity disorder was recorded only if two out of three agreed. Finally, a fourth neurologist confirmed the findings, who were also aware of the objectives of the study.
The authors say the findings are believed to be the first to link ADHD in to DLB. They believe their research shows a clear association between attention-deficit and hyperactivity disorder and dementia with Lewy bodies, concluding there is a “clearly a common process” between ADHD and dementia that occurs with aging.
European Journal of Neurology. 18, pp78-84. (January 2011). DOI: 10.1111/j.1468-1331.2010.03064.x
“Previous adult attention-deficit and hyperactivity disorder symptoms and risk of dementia with Lewy bodies: a case-control study. Golimstok et al.”