Parents and grandparents of people with attention-deficit/hyperactivity disorder (ADHD) are at increased risk of Alzheimer’s disease and dementia, according to a study findings published in the journal Alzheimer’s & Dementia.

“The findings suggest that there are common genetic and/or environmental contributions to the association between ADHD and dementia. Now we need further studies to understand the underlying mechanisms,” said study first author Le Zhang, a PhD student in the department of medical epidemiology and biostatistics at Karolinska Institutet in Sweden.

Zhang and colleagues investigated the incidence of Alzheimer’s disease and any dementia among more than 5 million relatives (parents, grandparents, and aunts and uncles) of 2.1 million individuals born in Sweden between 1980 and 2001. Among them, 3.2% had a diagnosis of ADHD.

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Parents of individuals with ADHD had a 55% higher risk of Alzheimer’s disease compared with parents of individuals without ADHD, according to the study. The risk of any dementia was 34% higher for parents of individuals with ADHD. Associations were stronger for early-onset Alzheimer’s disease and any dementia compared with late-onset disease.

On the whole, however, researchers pointed out that the absolute risk of dementia for parents of individuals with ADHD was low, at just 0.17%, during follow-up.

Meanwhile, grandparents of individuals with ADHD had approximately a 10% higher risk of Alzheimer’s disease and any dementia compared with grandparents of individuals without ADHD.

“We found that ADHD coaggregated with Alzheimer’s disease and any dementia within families, and the strength of association attenuated with decreasing degree of genetic relatedness,” researchers wrote. “Molecular genetic and family studies aiming to identify pleiotropic genetic variants and family-wide environmental risk factors contributing to both conditions are warranted.”

References

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. Published online September 9, 2021. doi: 10.1002/alz.12462

Link between ADHD and dementia across generations. News release. Karolinska Institutet. September 9, 2021. Accessed September 17, 2021.