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March 7, 2022
Alzheimer's disease is characterized by an aging-related progressive deterioration in cognition and ability for independent living. It is the most common form of dementia. Few studies, with limited sample sizes, have probed the relationship between ADHD and dementia, with conflicting results.
A Swedish study team used the country's universal system of population and health registers' linked through unique personal identification numbers - to examine patterns among the more than 2.1 million Swedes born between 1980 and 2001.
Each of these individuals was then linked to their biological relatives, parents, grandparents, uncles, and aunts through the Medical Birth Register and Multi-generation Register.
This generated three cohorts of relatives representing different levels of genetic relatedness: parents sharing half of their genes; grandparents sharing a quarter of their genes; and uncles and aunts who also share a quarter of their genes with index persons. After linking index persons to their biological relatives, the study cohorts contained more than 2.2 million parents, over 2.5 million grandparents, and almost a million uncles/aunts.
By the end of follow-up, 3,042 (0.13%) parents, 171,732 (6.82%) grandparents, and 1,369 (0.15%) uncles/aunts had a diagnosis of Alzheimer's. The numbers for any dementia were 3,792 (0.17%) for parents, 197,843 (7.86%) for grandparents, and 1,697 (0.18%) for uncles/aunts.
Parents of persons with ADHD were 34% more likely to have any dementia, and 55% more likely to have Alzheimer's. Among grandparents of persons with ADHD, the association dropped to 10-11% more likely for any kind of dementia. Among aunts and uncles, it dropped to a 14% greater likelihood of Alzheimer's(similar to grandparents) and a 4% greater chance of any dementia. In this case, however, the results were not statistically significant, probably due in part to the much smaller sample size
Both with parents and grandparents of persons with ADHD, the risk of early onset of any kind of dementia was well over twice as high as the risk of late-onset.
"We found that ADHD aggregated with AD [Alzheimer's disease] and any dementia within families, and the strength of association attenuated with decreasing degree of genetic relatedness," the authors concluded, and called for further studies to identify genetic variants and family-wide environmental risk factors contributing to both conditions. If verified by such studies, that would indicate a need for "investigation of early-life psychiatric prevention on the development of neurodegenerative diseases in older age."
Le Zhang, Ebba Du Rietz, Ralf Kuja-Halkola, MajaDobrosavljevic, Kristina Johnell, Nancy L. Pedersen, Henrik Larsson, ZhengChang, "Attention-deficit/hyperactivity disorder and Alzheimer's disease and dementia: A multi-generation cohort study in Sweden," Alzheimer's &Dementia (2021), published online,https://doi.org/10.1002/alz.12462.
The Background:
Stimulant medications (like methylphenidate and amphetamines) and non-stimulants (like atomoxetine and guanfacine) remain the first-line treatments for ADHD, but their long-term use is often constrained by parental concerns, side effects (reduced appetite, sleep disruption, cardiovascular effects), and the fact that roughly 30% of children respond only partially or not at all. These medications tend to help with attention and behavior, but they do less to address emotional regulation or broader physical health, leaving some parents to seek other safe, complementary treatments.
Nutritional approaches, including omega-3 fatty acids, are one such avenue. Oily fish is the natural source, but clinical trials typically rely on supplements instead, since they allow for precise dosing, avoid the heavy-metal exposure that can come with high fish intake, and sidestep the problem of inconsistent dietary habits. Two omega-3s stand out as particularly relevant: DHA, which supports brain structure and cell-to-cell communication, and EPA, which helps reduce brain inflammation and improve blood flow. Both influence the dopamine and serotonin systems implicated in ADHD.
The Study:
Previous meta-analyses have generally found only modest overall benefits with mixed results. This mixed-results pattern may reflect the fact that children who had low omega-3 levels to begin with stand to benefit more than those whose levels are already adequate. This meta-analysis set out to test that idea directly, asking whether a child's baseline omega-3 status predicts how well they respond to supplementation.
To be included, studies had to be randomized controlled trials (RCTs) involving children diagnosed with ADHD who did not have major coexisting medical conditions. Trials that used broad multinutrient interventions, where the effect of omega-3s specifically couldn't be isolated, were excluded.
The resulting analysis of seven RCTs covering 654 children found small overall improvements in ADHD symptoms with omega-3 supplementation, consistent with earlier meta-analyses. There was little variation across studies, but a clear signal of publication bias, which the authors did not attempt to statistically correct for.
Among four RCTs involving 369 children with low baseline omega-3 levels, supplementation produced a moderate improvement in ADHD symptoms, with consistent results across studies. By contrast, the six RCTs covering 559 children with normal or high baseline omega-3 levels showed no improvement at all, again with consistent results across studies.
The Results:
The authors concluded: this systematic review and meta-analysis offers preliminary evidence that children’s response to long-chain omega-3 supplementation for ADHD may depend on their starting omega-3 nutritional status. Larger effects emerged in the subgroups defined by individual studies as having low baseline levels, while normal, high, or unstratified groups showed little evidence of benefit. In other words, there may be a benefit to children with ADHD taking omega-3 supplements, but only if they are already deficient.
Even still, a sensitivity analysis limited to ADHD symptom-rating scales found only a numerically higher effect in the low-baseline group. This means that these results, though positive, are not considered statistically significant.
The Take-Away:
Given that the evidence rests on just seven trials, that “low baseline” was defined differently across studies (using different biological markers and thresholds), and that several subgroup comparisons were not planned in advance, the authors caution that these findings should be treated as hypothesis-generating rather than conclusive.
The Background:
Previous research has suggested that people with ADHD have higher rates of death than those without the condition. Until now, many of those studies lacked the detail needed to untangle why this might be the case. A recent meta-analysis of eight separate studies reported that ADHD roughly doubled the risk of death, and it hinted that factors like socioeconomic status and other mental illnesses might help explain the link.
The Study:
To explore this in more detail, researchers used the US National Health Interview Survey, a nationally representative prospective cohort of just over 52,000 adults. Survey records were linked with the National Death Index, and participants were followed from the date of interview until death or December 31, 2019, whichever came first. The main outcome was death from any cause. With a median follow-up of just under eight years, there were 6,024 deaths recorded.
When the team adjusted their analysis for age, sex, ethnicity, and the year of the survey, having ADHD was associated with a 58% higher risk of death. Controlling further for family income and educational level reduced that increased risk slightly, to 50%.
Controlling for health conditions (like high blood pressure, diabetes, stroke, heart disease, and cancer) and lifestyle factors (smoking, alcohol use, physical activity, and body weight) also reduced the association to about 46%.
By contrast, when the researchers adjusted for two psychiatric conditions (anxiety and depression) commonly found alongside ADHD, the link between ADHD and higher mortality disappeared statistically. In other words, once anxiety and depression were taken into account, ADHD itself was no longer associated with a clearly measurable increase in the risk of death.
What Does This Mean?
The authors conclude that the apparent effect of ADHD on mortality seems to operate largely through accompanying mental illness, and to a lesser extent through lifestyle and physical health problems. They suggest that treating and managing these co-occurring issues (through medications, therapy, and behavioral interventions) might help reduce the risk of premature death in people with ADHD, although they note that further evidence is needed.
The Background:
Dementia is a rapidly growing public health problem affecting more than 50 million people worldwide. Nearly 10 million new cases are diagnosed each year, and that number is expected to almost triple by 2050. The most common form is Alzheimer’s disease, accounting for roughly 60–70% of cases, followed by vascular dementia at around 20%. Other types include dementia with Lewy bodies, Parkinson’s disease dementia, and frontotemporal dementia. While no cure exists, managing modifiable risk factors (such as high blood pressure, smoking, physical inactivity, and poorly controlled diabetes) can delay or slow both the onset and progression of the condition.
Several studies have reported an elevated dementia risk among people with ADHD, and a number of mechanisms may explain this association. These include shared genetic or neurobiological vulnerabilities, reduced cognitive reserve (leaving the brain less resilient to age-related damage), and greater lifetime exposure to other established dementia risk factors.
Earlier reviews explored the possible link between ADHD and dementia, but tended toward a broader scope (incorporating other neurodegenerative disorders or mixing study designs), which introduced substantial variability and precluded quantitative synthesis. The relevant research literature has also expanded considerably since those reviews appeared.
The Study:
This meta-analysis restricted inclusion to case-control and cohort studies, yielding five that met the criteria. One was a case-control study with 400 participants; the other four were cohort studies collectively covering 3.7 million individuals, two retrospective and two prospective.
The Results:
Pooling the four cohort studies, individuals with ADHD showed approximately two-and-a-half times the dementia risk of those without the diagnosis. There was no indication of publication bias.
The Take-Away:
The authors concluded that ADHD is associated with a significantly increased risk of all-cause dementia in later life, while noting that its relationship to specific dementia subtypes remains less clear and warrants attention in future research.
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