A study involving 360 patients with degenerative dementia (109 people with dementia with Lewy bodies (DLB) and 251 with Alzheimer's) and 149 matched controls, has found that 48% of those with DLB had previously suffered from adult ADHD. This compares with 15% found in both the control group and the group with Alzheimer's. DLB tends to be under-diagnosed, but is thought to account for around 10% of dementia cases in older people.
ADHD and DLB are thought to both involve the same neurotransmitter pathway problems.
(2011). Previous adult attention-deficit and hyperactivity disorder symptoms and risk of dementia with Lewy bodies: a case-control study.
European Journal of Neurology. 18(1), 78 - 84.