Summary: People diagnosed with attention-deficit/hyperactivity disorder (ADHD) had a 34% higher risk of being diagnosed with dementia compared with those without ADHD. The risk of Alzheimer’s disease — the most common form of dementia — was 55% higher among relatives of people with ADHD.
Source: Karolinska Institute
A large, nationwide study from Karolinska Institutet in Sweden reports a familial association between ADHD and dementia spanning generations. Published in Alzheimer’s & Dementia, the study found that parents and grandparents of individuals with ADHD were more likely to receive a dementia diagnosis than relatives of people without ADHD.
“These results point to shared genetic and/or familial environmental factors that may underlie the link between ADHD and dementia. Further research is needed to unpack the mechanisms,” says Le Zhang, PhD student at the Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, and first author of the study.
ADHD is a neurodevelopmental condition characterized by inattention, impulsivity and hyperactivity. It affects an estimated 3% of adults globally. Diagnoses of ADHD have risen in recent decades as awareness and diagnostic practices have increased, but because systematic long-term research on ADHD and later-life cognitive disorders has been limited, earlier studies gave mixed results.
To address these gaps, the researchers used national population registers to follow a comprehensive cohort of people born in Sweden between 1980 and 2001. The study included more than two million “index persons,” about 3.2% of whom had an ADHD diagnosis, and linked them to over five million biological relatives — parents, grandparents, and uncles and aunts — to track dementia diagnoses across generations.
Key findings included a 34% higher overall risk of dementia among parents of individuals with ADHD, compared with parents of those without ADHD. The risk of Alzheimer’s disease was markedly elevated — 55% higher in those same parents. The study also found that parents of individuals with ADHD were more likely to experience early-onset dementia rather than late-onset dementia.
Despite these relative increases, the absolute risk in the parent cohort was small during the study’s follow-up: only 0.17% of parents received a dementia diagnosis. The pattern of association weakened with more distant relatives but remained detectable. For example, grandparents of individuals with ADHD had about a 10% higher risk of dementia compared with grandparents of those without ADHD.
The observational design means causation cannot be established. The authors outline several plausible explanations for the observed familial clustering. Shared genetic variants that influence both ADHD and neurodegenerative disease are one possibility. Shared family-level environmental factors — such as socioeconomic conditions, lifestyle, or long-term health exposures — could also contribute. Another hypothesis is that ADHD increases the risk of physical health problems that subsequently raise dementia risk.
Funding: This research was supported by grants from the Swedish Council for Health, Working Life and Welfare, the Swedish Research Council, the Swedish Brain Foundation, the European Union’s Horizon 2020 programme (Marie Skłodowska-Curie), the Fredrik & Ingrid Thurings Stiftelse and the Karolinska Institutet Research Foundation.
Co-authors Ebba Du Rietz and Henrik Larsson reported conflicts of interest outside the submitted work.
About this ADHD and dementia research news
Author: Press Office
Source: Karolinska Institute
Contact: Press Office – Karolinska Institute
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Original Research: Open access. “Attention-deficit/hyperactivity disorder and Alzheimer’s disease and any dementia: a multi-generation cohort study in Sweden” by L. Zhang, E. Du Rietz, R. Kuja-Halkola, M. Dobrosavljevic, K. Johnell, N. L. Pedersen, H. Larsson, and Z. Chang. Alzheimer’s and Dementia (study details reported in the journal).
Abstract
Attention-deficit/hyperactivity disorder and Alzheimer’s disease and any dementia: a multi-generation cohort study in Sweden
Introduction
This study investigated whether ADHD, a neurodevelopmental disorder characterized by attentional and behavioral symptoms, is associated with Alzheimer’s disease (AD) and other forms of dementia across generations.
Methods
Researchers assembled a nationwide cohort of individuals born between 1980 and 2001 and linked these index persons to biological relatives (parents, grandparents, uncles/aunts) using Swedish national registers. Cox proportional hazards models were used to estimate associations across generations.
Results
Among relatives of 2,132,929 index persons, the study reported that 3,042 parents, 171,732 grandparents, and 1,369 uncles/aunts had a diagnosis of Alzheimer’s disease. Parents of individuals with ADHD had a significantly increased risk of AD (hazard ratio 1.55; 95% confidence interval 1.26–1.89). The associations decreased but remained elevated among grandparents and uncles/aunts. The link was stronger for early-onset AD than for late-onset AD. Comparable results were observed for any dementia diagnoses.
Discussion
The study demonstrates an association between ADHD and Alzheimer’s disease and other dementias that extends across generations. The pattern of decreasing association with more distant genetic relatedness supports the interpretation of shared familial risk factors — genetic and/or environmental — linking ADHD and dementia. Further research should explore the specific biological and environmental pathways responsible for these findings and assess how they may inform prevention and early-detection strategies for dementia in families affected by ADHD.