According to Swedish researchers, parents and grandparents of people with ADHD have a higher risk of Alzheimer’s and dementia than people without ADHD in their families. According to the findings, parents of an ADHD child have a 34% increased risk of dementia and a 55% increased risk of Alzheimer’s. Grandparents are at an 11 percent higher risk of developing either condition.
A large study at Sweden’s Karolinska Institutet discovered a link between ADHD and dementia across generations. The study, published in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association, found that parents and grandparents of ADHD individuals had a higher risk of dementia than those with ADHD children and grandchildren.
“The findings imply that the association between ADHD and dementia is caused by shared genetic and/or environmental factors. More research is needed to understand the underlying mechanisms “Le Zhang, a Ph.D. student at Karolinska Institutet’s Department of Medical Epidemiology and Biostatistics, is the study’s first author.
Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterized by inattention, impulsiveness, and hyperactivity. It is estimated that 3% of adults worldwide are affected.
The ADHD patients were linked to more than 5 million biological relatives – parents, grandparents, aunts, and uncles; using national registries. They then looked to see if these relatives had dementia or Alzheimer’s disease. The findings imply that the association between ADHD and dementia is caused by shared genetic and/or environmental factors.
Le Zhang
The number of new ADHD diagnoses has risen dramatically in recent decades, owing to increased awareness and understanding of the disorder. However, because the diagnosis is still relatively new, there have only been a few small studies on the development of dementia in people with ADHD, with often contradictory results.
The current study sought to address this by examining the extent to which older generations of ADHD patients were diagnosed with dementia. The study included over two million people born in Sweden between 1980 and 2001, with approximately 3.2 percent diagnosed with ADHD. Using national registries, the researchers linked these people to over five million biological relatives, including parents, grandparents, uncles, and aunts, and looked into how much dementia these relatives had.
The researchers discovered that parents of ADHD children had a 34% higher risk of dementia than parents of non-ADHD children. The risk of Alzheimer’s disease, the most common type of dementia, was found to be 55% higher in parents of ADHD patients. Individuals with ADHD were more likely to have parents who had early-onset dementia than those who had late-onset dementia.
The researchers note that the parent cohort’s absolute risk of dementia was low; only 0.17 percent of the parents were diagnosed with dementia during the follow-up period. The association was weaker for second-degree relatives of people with ADHD, such as grandparents, uncles, and aunts. Grandparents of ADHD patients, for example, had a 10% higher risk of dementia than grandparents of non-ADHD patients.
While the study was unable to establish a cause-and-effect relationship, the researchers presented several potential explanations that can be investigated further 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, the study’s last author and researcher at Karolinska Institutet’s Department of Medical Epidemiology and Biostatistics. “Another possible explanation is that ADHD raises the risk of physical health problems, which raises the risk of dementia.”
The ADHD patients were linked to more than 5 million biological relatives — parents, grandparents, aunts and uncles — using national registries. They then looked to see if these relatives had dementia or Alzheimer’s disease.
Parents did have a significantly increased risk of dementia, but the risk decreased with the distance of family relation, according to the researchers. Grandparents were at a lower risk than parents, and aunts and uncles were even less at risk.
Even though ADHD parents had a significantly increased risk of dementia, their absolute risk of the degenerative brain condition remained low, according to the study’s authors. In total, less than 0.2 percent of the parents identified in the study were diagnosed with dementia.
