November 1, 2023
An international team of researchers recently published the first meta-analysis of studies examining the prevalence of ADHD in older adults, with a particular focus on those fifty and older. They also looked at rates of treatment.
Since clinical evaluations a reconsidered the gold standard in diagnosing ADHD, and validated rating scales are considered more of a preliminary screening tool, the team distinguished between the two and ran two separate meta-analyses:
· Using validated ADHD rating scales. Combining nine studies with just over 32,000 participants, the team reported a prevalence of 2.2 percent. However, since the studies were not uniform in fixing the minimum end of their age ranges, constraining the results to persons 50 and older lowered the prevalence to 1.5 percent.
· Using clinical diagnoses. Combining seven studies with 11.7 million participants, they found a crude prevalence of 0.23 percent, which, after removing persons under 50, was adjusted to 0.19 percent. Limiting the results to the use of national registries further reduced the prevalence to 0.14 percent.
That means there's an order of magnitude (tenfold) difference between the two estimates of prevalence.
Recognizing that clinical diagnoses are the preferred means of diagnosis, the authors wrote, "methodological aspects need to be considered when interpreting the gap between the pooled prevalence estimates based on different assessment methods. The estimates from studies based on research diagnosis [ADHD rating scales] may overestimate the prevalence of ADHD in older adults. ... Thus, screening assessment tools for ADHD should only be used as the first step of a more comprehensive clinical ADHD assessment."
On the other hand, the authors also see an indication "that clinicians, to some extent, might fail to recognize and properly treat ADHD symptoms in older adults. Clinical presentation of ADHD may change with age, with inattentive symptoms becoming more prevalent than hyperactivity and impulsivity."
The team also performed a third meta-analysis, to look at ADHD pharmacological treatment rates among older adults. For this one, they pooled four studies encompassing over 9.2 million persons. After constraining the results to those fifty and older, they found a prevalence of only 0.02%. This points to a wide gap between rates of diagnosis and rates of treatment, even after noting that only one of the studies included data on non-pharmacological treatment.
MajaDobrosavljevic, Carmen Solares , Samuele Cortese, Henrik Andershed, Henrik Larsson, "Prevalence of attention-deficit/hyperactivity disorder in older adults: A systematic review and meta-analysis," Neuroscience and biobehavioral reviews (2020), 118, 282-289, https://doi.org/10.1016/j.neubiorev.2020.07.042.