To assess the prevalence of early-onset dementia, researchers examined data from 95 studies, including data on 2.76 million people in 74 of these studies for a 5-year age-band meta-analysis. The age-standardized prevalence of young onset dementia increased from 1.1 per 100,000 population among adults 30 to 34 years old to 77.4 per 100,000 among adults 60 to 64 years old, the analysis found.
When researchers looked at all ages from 30 to 64 years together, they calculated an overall global age-standardized early-onset dementia prevalence of 119 per 100,000 population, or approximately 3.9 million individuals worldwide, according to the report in JAMA Neurology.
"The prevalence rates we found are not surprising, but a substantiation of previous estimates, and also highlight the worldwide prevalence of young-onset dementia," said senior study author Sebastian Kohler of the Alzheimer Center Limburg and Maastricht University in The Netherlands.
Because dementia is more commonly associated with older adults, clinicians may overlook the potential for an early-onset dementia diagnosis in younger patients and instead diagnose these patients with conditions such as burn-out or depression, Kohler said by email. This can lead to a long delay in arriving at the correct diagnosis while patients struggle with situations at home and at work that are related to dementia, Kohler said.
In subgroup analysis, researchers found a similar prevalence of early onset dementia in men (216.5 per 100,000 population) and women (293.1 per 100,000 population).
There was a lower prevalence of young-onset dementia in high-income countries (663.9 per 100,000 population) than in upper-middle-income countries (1873.6 per 100,000 population) and lower-middle-income countries (764.2 per 100,000 population).
Overall, 46 studies were done in high-income countries, 18 were done in upper-middle-income countries and 16 were done in lower-middle-income countries. Only one study was conducted in a low-income country.
The analysis included 27 studies done in Europe, 33 conducted in Asia, 7 from North America, 6 from South America, 4 done in Africa, and 4 conducted in Oceania.
One limitation of the analysis is that few studies were from Africa or low-income countries, the study team notes. Almost half of the studies in the analysis only included people 60 to 64 years old, and estimates of 5-year age bands may have been conservative as a result, they add.
While the vast majority of dementia cases occur after age 65, the study results do highlight the potential for cases to develop at much younger ages, said Dr. David Knopman, a professor of neurology at the Mayo Clinic in Rochester, Minnesota, and author of an editorial accompanying the study.
Based on the prevalence found in the current study and others, young-onset dementia (YOD) cases represent just 3%-5% of all dementia patients, Dr. Knopman notes in the editorial. "This low prevalence has a practical consequence because it directly translates into a lack of familiarity with YOD in the primary care and frontline neurology clinician communities," he writes.
"The take-home message for frontline and specialty physicians is that dementia under age 65 years does occur and the possibility cannot be simply dismissed on the basis of age," Dr. Knopman said by email.
SOURCE: https://bit.ly/3hPz1Gv and https://bit.ly/2ToxGNC JAMA Neurology, online July 19, 2021.
By Lisa Rapaport
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