New Study Finds Link Between Adult ADHD and Dementia Risk

An association exists between adult ADHD and an increased risk of dementia, according to a new study led by Stephen Levine, PhD, of the school of public health at University of Haifa in Israel.¹

“The present study results showed that an adult ADHD diagnosis was associated with a 2.77-fold increased risk of incident dementia,” the investigators wrote.

Many older adults develop dementia, and the investigators said recognizing risk and preventive factors for dementia is “an international priority.” In 2022, the estimated number of US individuals aged >65 years old with dementia was 6.5 million—that number is predicted to increase to 13.8 million by 2060.

Since previous research suggested that adult ADHD mimics the cognitive symptoms of dementia, the investigators wanted to see if there was a link between adult ADHD and the increased risk of dementia.

“It may be plausible that adult ADHD reflects a brain pathobiological process that reduces the ability to compensate for the effects of later-life neurodegenerative and cerebrovascular processes,” the team wrote. “Less cognitive and brain reserve may result in pathobiological processes of ADHD that, in turn, reduce compensatory abilities.”

Previous research had identified 6 health outcomes—for example, depression, midlife hypertension, smoking, type 2 diabetes, and low levels of education and physical activity—which are modifiable dementia risk factors and consequences of ADHD.²

Levine and colleagues conducted a national cohort study of 109,218 members from the nonprofit Israel health maintenance organization, Meuhedet Healthcare Services. Participants were born between 1933 – 1952 (aged 51 – 70 years; mean age: 57.7), and they entered the cohort in January 2003. Over half of the participants were female (51.7%).At the time of entry, no participants had an ADHD or dementia diagnosis. Participants who had a diagnosis for dementia and a diagnosis of ADHD by December 2002 were not eligible for the study. Participants were then followed up on through February 2020.1

During the follow-up, 0.7% of participants (n = 730) received an adult ADHD diagnosis and 7.1% (n = 7726) received a dementia diagnosis.

Dementia developed in 13.2% (n = 96) of participants with ADHD and 7% (n = 7630) of participants without ADHD.

The team found in the primary analysis that the presence of ADHD was significantly associated with an increased risk of dementia (unadjusted hazard ratio [HR], 3.62; 95% CI, 2.92 – 4.49; P <.001); adjusted HR, 2.77; 95% CI, 2.11 – 3.63; P <.001).

As for the test for the proportional hazard assumption, there was not a statistically significant association between ADHD and the risk of dementia (χ2 = 2.42; P = .12).

There was also no significant increase in the risk of dementia associated with adult ADHD for participants who take psychostimulant medication.

“This association requires further study before causal inference is plausible,” the investigators wrote. “There are multiple risks (eg, increased blood pressure or heart rate) and benefits (eg, reduced risk of accidents and injuries) to weigh before considering psychostimulant medication as a dementia prevention strategy.”

The team noted that this finding of the addition of psychostimulants could have different interpretations.

“It is possible that ADHD treated with medication reflects more severe ADHD compared with ADHD not treated with prescribed psychostimulants, which may reflect milder symptoms or even a less-accurate diagnosis,” the investigators wrote.

References

1. ^{Levine, S, Rotstein A, Kodesh, A, et al. Adult Attention-Deficit/Hyperactivity Disorder and the Risk of Dementia. JAMA Network Open. 2023. doi:10.1001/jamanetworkopen.2023.38088}
2. ^{Zhang L, Du Rietz E, Kuja-Halkola R, et al. Attention-deficit/hyperactivity disorder and Alzheimer’s disease and any dementia: a multi-generation cohort study in Sweden. Alzheimers Dement. 2022;18(6):1155-1163. doi:10.1002/alz.12462}