Adults with attention-deficit/hyperactivity disorder (ADHD) are nearly three times more likely to develop dementia than those without the condition, according to a study.

ADHD is a neurodevelopmental disorder characterised by excessive amounts of inattention, hyperactivity, and impulsivity.

Researchers found the presence of adult ADHD was associated with a significantly higher risk of dementia even when other risk factors for dementia were taken into account, such as cardiovascular conditions.

ADHD in adults may materialise as a neurological process that reduces the ability for them to compensate for the effects of cognitive decline later in life, they noted.

"Physicians, clinicians and caregivers who work with older adults should monitor ADHD symptoms and associated medications," said Abraham Reichenberg, a professor at the Department of Psychiatry at the Icahn School of Medicine at Mount Sinai in the US.

The study, published in JAMA Network Open, followed more than 100,000 older adults in Israel over 17 years to examine if adults with ADHD are at increased risk for dementia, including Alzheimer’s disease.

"By determining if adults with ADHD are at higher risk for dementia and if medications and/or lifestyle changes can affect risks, the outcomes of this," said Michal Schnaider Beeri, at Brain Health Institute (BHI) at Rutgers University.

"Symptoms of attention deficit and hyperactivity in old age shouldn’t be ignored and should be discussed with physicians,” said Stephen Levine, a professor at the School of Public Health at the University of Haifa in Israel.

The study suggests ADHD treatment incorporating psychostimulants may help reduce the risk of dementia in adults with ADHD as psychostimulants are known to modify the trajectory of cognitive impairment. However, researchers said future studies should examine in more detail the impact of medications in patients with ADHD and how they could affect risk.