Link between ADHD and dementia across generations

Date:
September 9, 2021
Source:
Karolinska Institutet
Summary:
A large study has found a link between ADHD and dementia across
generations. The study shows that parents and grandparents of
individuals with ADHD were at higher risk of dementia than those
with children and grandchildren without ADHD.



FULL STORY ==========================================================================
A large study at Karolinska Institutet in Sweden has found a link
between ADHD and dementia across generations. The study, published in Alzheimer's & Dementia: The Journal of the Alzheimer's Association, shows
that parents and grandparents of individuals with ADHD were at higher
risk of dementia than those with children and grandchildren without ADHD.


==========================================================================
"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," says the
study's first author Le Zhang, PhD student at the Department of Medical Epidemiology and Biostatistics at Karolinska Institutet.

ADHD (attention-deficit/hyperactivity disorder) is a neurodevelopmental disorder characterized by inattention, impulsiveness and hyperactivity. It affects an estimated 3 percent of adults worldwide.

The number of new ADHD diagnoses has increased dramatically in
the last decades amid increasing awareness and knowledge about the
disorder. However, since the diagnosis is still relatively new, there
has only been a limited number of small studies on the development of
dementia in people with ADHD, often with conflicting results.

In the current study, the researchers wanted to overcome this by examining
to what extent older generations to individuals with ADHD were diagnosed
with dementia. The study looked at more than two million people born in
Sweden between 1980 and 2001, of whom around 3.2 percent were diagnosed
with ADHD.

Using national registries, the researchers linked these persons to
over five million biological relatives, including parents, grandparents
and uncles and aunts, and investigated to what extent these relatives
developed dementia.

The researchers found that parents of individuals with ADHD had 34 percent higher risk of dementia than parents of individuals without ADHD. The risk
of Alzheimer's disease, the most common type of dementia, was 55 percent
higher in parents of individuals with ADHD. Individuals with ADHD were
more likely to have parents with early-onset dementia than late-onset.

The researchers note that the absolute risk of dementia was low for
the parent cohort; only 0.17 percent of the parents were diagnosed with dementia during the follow-up period.

The association was lower for second-degree relatives of individuals with
ADHD, i.e. grandparents and uncles and aunts. For example, grandparents of individuals with ADHD had 10 percent increased risk of dementia compared
to grandparents of individuals without ADHD.

While the study is unable to determine a cause-and-effect relationship,
the researchers present several potential explanations that can be
explored in future research.

"One could imagine that there are undiscovered genetic variants
that contribute to both traits, or family-wide environmental
risk factors, such as socioeconomic status, that may have an
impact on the association," says Zheng Chang, researcher at
the Department of Medical Epidemiology and Biostatistics at
Karolinska Institutet, and the study's last author. "Another
possible explanation is that ADHD increases the risk of physical
health conditions, which in turn leads to increased risk of dementia." ========================================================================== Story Source: Materials provided by Karolinska_Institutet. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Le Zhang, Ebba Du Rietz, Ralf Kuja‐Halkola, Maja
Dobrosavljevic,
Kristina Johnell, Nancy L. Pedersen, Henrik Larsson, Zheng Chang.

Attention‐deficit/hyperactivity disorder and Alzheimer's
disease and any dementia: A multi‐generation cohort study
in Sweden.

Alzheimer's & Dementia, 2021; DOI: 10.1002/alz.12462 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/09/210909123905.htm

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