ADHD Linked to Lewy Body Dementia
Dementia with Lewy bodies (DLB) is a neurodegenerative condition characterized by progressive, disabling cognitive impairment. It is second only to Alzheimer’s disease as the most common cause of degenerative dementia in the elderly. A recent study published in the January issue of the European Journal of Neurology finds that adults with attention-deficit/hyperactivity disorder (ADHD) may be at an increased risk for developing the disease.
ADHD and Lewy Body Demenia Linked by Dysfunction in Neurotransmitter Pathway
Lewy bodies are abnormal protein deposits that disrupt the brain’s normal functioning. In addition to cognitive deficits, common symptoms include hallucinations and motor abnormalities similar to those in Parkinson’s disease.
Dr. Angel Golimstock and colleagues at the Hospital Italiano Buenos Aires in Argentina collected data on 109 patients with DLB, 251 patients with Alzheimer’s disease and 149 healthy controls between 2000 and 2005. The frequency of ADHD symptoms during adult life was evaluated using the DSM-IV criteria and the Wender Utah Rating Scale.
The researchers found that the prevalence of ADHD symptoms was significantly higher in patients with Lewy body dementia compared to either the Alzhieimer’s patients or the controls. The frequency of preceding ADHD symptoms in DLB cases was 47.8% versus 15.2% in Alzheimer’s and 15.1% in the healthy patients.
The researchers explain that both conditions appear to have a common neurotransmitter pathway dysfunction. Previous observations have noted that both children and adults with ADHD have abnormally high densities of dopamine transporters which remove excess dopamine from the synapses, leading to a depletion of the neurotransmitter. Loss of dopamine in the basal ganglia of the brain is also seen in patients with numerous Lewy bodies.
The findings may also be useful for Parkinson’s disease patients, as they also have low levels of tonic dopamine.
The study authors warn that their findings are preliminary, and that this is the first study in which an association between clinical ADHD and DLB has been established, but doesn’t prove cause and effect. They conclude that “further investigation will contribute to increase our knowledge about both diseases.”
Lewy body dementia affects about 1.3 million people in the United States, according to statistics from the Lewy Body Dementia Association. While exact prevention efforts to avoid the disease are yet unknown, those who maintain their general health throughout adulthood by eating a proper diet, exercising and avoiding tobacco smoke exposure seem better able to resist the disease, says James B Leverenz MD, chair of the Lewy Body Dementia Association’s scientific advisory council.
Golimstok A, Rojas JI, et al. "Previous adult attention-deficit and hyperactivity disorder symptoms and risk of dementia with Lewy bodies: a case–control study", European Journal of Neurology, DOI: 10.1111/j.1468-1331.2010.03064.x