A large study of the Karolinska Institutet in Sweden found a link between dementia and ADHD across generations. The study found that parents and grandparents of individuals with ADHD were at a higher risk of dementia than those with children and grandchildren without ADHD.
There Research was published in the scientific journal Alzheimer’s & Dementia : The Journal of Alzheimer’s Association.
Dementia and ADHD: This is why they are related
The findings suggest that there are common genetic and / or environmental contributions to the association between dementia and ADHD. We now need more studies to understand the underlying mechanisms“Says the first author of the study Le Zhang, researcher at the Department of Medical Epidemiology and Biostatistics of the Karolinska Institutet.
ADHD ( attention deficit / hyperactivity disorder) is a neurodevelopmental disorder characterized by inattention, impulsivity and hyperactivity. It affects around 3% of adults worldwide.
The number of new ADHD diagnoses has increased dramatically in recent decades thanks to the growing awareness and knowledge of the disorder. However, as the diagnosis is still relatively new, there have only been a limited number of small studies on the development of dementia in people with ADHD, often with mixed results.
In the new research, the scholars wanted to overcome this problem by examining the extent to which older generations of individuals with ADHD have been diagnosed with dementia. The study looked at more than two million people born in Sweden between 1980 and 2001, of which approximately 3.2% were diagnosed with ADHD.. Using national registries, the researchers linked these people to more than five million biological relatives, including parents, grandparents and uncles and aunts, and studied the extent to which these relatives developed dementia.
The researchers found that parents of individuals with ADHD had a 34% higher risk of dementia than parents of individuals without ADHD. The risk of Alzheimer’s disease, the most common type of dementia, was 55% higher in the parents of individuals with ADHD. Individuals with ADHD were more likely to have parents with early-onset dementia than those with late-onset.
The researchers note that the absolute risk of dementia was low for the parental cohort; only 0.17% of 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, the grandparents of individuals with ADHD had a 10% increased risk of dementia compared to the grandparents of individuals without ADHD.
Although the study cannot determine a cause-and-effect relationship, the researchers present several potential explanations that can be explored in future research.
“One might imagine that there are unknown genetic variants contributing to both traits, or family-level environmental risk factors, such as socioeconomic status, that could impact the association.“, he claims Zheng Chang, researcher at the Department of Medical Epidemiology and Biostatistics at Karolinska Institutet and latest author of the study. “Another possible explanation is that ADHD increases the risk of physical health conditions, which in turn leads to an increased risk of dementia.”
Not just dementia and ADHD: parental type 1 diabetes can also lead to attention deficit / hyperactivity disorder in offspring
Children whose parents have type 1 diabetes have a higher risk of being diagnosed with attention deficit / hyperactivity disorder (ADHD), according to one study published online in the scientific journal Diabetes Care.
To be able to trace individuals with type 1 diabetes and their offspring, Jianguang Ji, MD, Ph.D., of Lund University in Sweden, and colleagues used the Swedish National Hospital Discharge Registry and the Swedish Outpatient Patient Registry, which were linked to the Swedish multi-generation registry.
Researchers identified 15,615 individuals born after their parents were diagnosed with type 1 diabetes. The offspring of patients diagnosed with diabetes had a significantly increased risk of ADHD (risk ratio [HR], 1.29), when checking for confounding variables. Although not statistically significant, maternal type 1 diabetes was associated with an increased risk of ADHD (HR, 1.35) compared to paternal type 1 diabetes (HR, 1.20). This means that there is not only a link between dementia and ADHD but also between parents with type 1 diabetes and offspring diagnosed with ADHD.
“In this reteospective cohort study, we found that a parental history of T1D was associated with a 29% increased risk of being diagnosed with ADHD,” the authors write. “The underlying mechanisms need to be explored in future studies ”.