ADHD in Adults Associated With Higher Risk for Dementia With Lewy Bodies

Attention-deficit/hyperactivity disorder (ADHD) in adults is associated with an increased risk of developing dementia with Lewy bodies (DLB), according to study findings published in The American Journal of Geriatric Psychiatry.

Previous research has suggested a link between ADHD and conversion to dementia, although the type of dementia is unclear. Researchers conducted a prospective observational cohort study to evaluate the relationship between ADHD as a risk factor for DLB.

The study was conducted at the Association Lewy Body Disease (ALBA) in Buenos Aires, Argentina, and at the Italian Hospital Medical Care Program (IHMCP) from February 2, 2007, to December 31, 2012. For inclusion, the researchers considered patients aged 45 to 70 with cognitive complaints or health screenings for early diagnosis of cognitive impairment who presented to the neurology service at the IHMCP or ALBA.

The analysis was conducted in two patient groups: patients diagnosed with adult ADHD and healthy patients without ADHD. Participants taking psychoactive medications, treated with ADHD medications for more than 5 months, or taking medications at baseline were excluded. Those taking a benzodiazepine or hypnotic for the indication of insomnia were permitted for inclusion. 

Patients were diagnosed according to the Diagnostic and Statistical Manual of Mental Disorders (DSM) IV, Text Revision (TR) criteria. A total of 161 participants with ADHD and 109 without ADHD were included in the study at baseline.

By the end of the average follow-up period of 12.1 years, dementia incidence was significantly increased among patients with ADHD compared to those without ADHD, with 87.1% (n=27) of patients developing dementia from the ADHD cohort. 

The most common type of dementia was DLB, with 95% (n=19) of cases from the ADHD cohort. Other frequent types of dementia included Alzheimer disease (14.1%) and vascular dementia (11.11%), with no significant differences between the study and comparator groups.  

Nonamnestic mild cognitive impairment (MCI) was present among 67.1% of patients with ADHD (n=108) compared to 17.4% (n=19) in the comparator group. Depression was significantly increased among patients with ADHD, as this group consisted of 77.27% (n=85) of all cases in this study. In the follow-up period, there were no significant differences in mortality. 

The average survival time among patients in the ADHD cohort was 14,628 (Standard Error, 0.0978; 95% CI, 14,436-14,820). After 15 years, the survival proportion without dementia among patients with ADHD was 62.9% and was 92.5% in the control population. There was also a significant difference reported between patients with ADHD and patients in the control group with conversions to LBD.

The multivariate adjusted model revealed hazard ratios of 3.33 (95% CI, 1.0915-10.1699) for dementia and 54.54 (95% CI, 7.4849-397.5028) for LBD among patients with ADHD. 

Study limitations included a lack of pathological anatomy confirming the dementia cases, the lack of information regarding vascular risk factors, and a small number of participants. 

“Future studies should be carried out to determine the mechanisms underlying this existing relationship and to investigate preventive measures acting on patients who present a risk profile for cognitive impairment,” the researchers concluded.