Attention-deficit/hyperactivity disorder (ADHD) is linked to Alzheimer’s disease (AD) and other types of dementia throughout generations. The relationships weakened as genetic relatedness decreased, indicating a shared familial risk for ADHD and AD. ADHD is a common neurodevelopmental disease characterized by poor sustained attention, poor impulse control, and hyperactivity.
A big study at Sweden’s Karolinska Institutet discovered a relationship 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 adults had a higher risk of dementia than those with ADHD children and grandkids.
“The findings imply that the link 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.
The findings imply that the link between ADHD and dementia is caused by shared genetic and/or environmental factors. More research is needed to understand the underlying mechanisms.
Le Zhang
Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterized by inattention, impulsiveness, and hyperactivity. It is estimated that 3% of adults globally are affected.
The incidence of new ADHD diagnoses has risen considerably in recent decades, owing to increased awareness and understanding of the illness. However, because the diagnosis is still relatively recent, there have only been a few short investigations on the development of dementia in patients with ADHD, with often contradictory results.
The current study sought to address this issue by investigating the extent to which elder generations of ADHD patients were diagnosed with dementia. The study included almost two million Swedish people born between 1980 and 2001, with around 3.2 percent diagnosed with ADHD. Using national registries, the researchers linked these individuals to almost five million biological relatives, including parents, grandparents, uncles, and aunts, and assessed the extent to which these relatives had dementia.
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 shown to be 55% greater 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 observe that the parent cohort’s absolute risk of dementia was modest; only 0.17 percent of the parents were diagnosed with dementia throughout the follow-up period.
The relationship was weaker for second-degree relatives of those 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 numerous alternative hypotheses 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, researcher at Karolinska Institutet’s Department of Medical Epidemiology and Biostatistics and the study’s last author. “Another probable explanation is that ADHD increases the risk of physical health issues, which in turn increases 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 next looked to see if these relatives had dementia or Alzheimer’s disease.
Parents did have a significantly elevated risk of dementia, but the risk decreased with the distance of family link, according to the study. Grandparents were at a lower risk than parents, while aunts and uncles were much less at risk.
Even though ADHD parents had a significantly elevated risk of dementia, their absolute risk of the degenerative brain disorder remained modest, according to the study’s authors. In total, less than 0.2 percent of the parents identified in the study were diagnosed with dementia.
