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Hendriks S, Peetoom K, Bakker C, van der Flier WM, Papma JM, Koopmans R, Verhey FR, de Vugt M, Köhler S, Young-Onset Dementia Epidemiology Study Group, Withall A, Parlevliet JL, Uysal-Bozkir Ö, Gibson RC, Neita SM, Nielsen TR, Salem LC, Nyberg J, Lopes MA, Dominguez JC, De Guzman MF, Egeberg A, Radford K, Broe T, Subramaniam M, Abdin E, Bruni AC, Di Lorenzo R, Smith K, Flicker L, Mol MO, Basta M, Yu D, Masika G, Petersen MS, Ruano L. Global Prevalence of Young-Onset Dementia: A Systematic Review and Meta-analysis. JAMA Neurol. 2021 Sep 1;78(9):1080-1090. PubMed.
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Mayo Clinic
The vast majority of research in the dementia field has focused on late-onset dementia. Historically, initial studies focused on estimating the prevalence and incidence, followed by identifying risk factors and biomarkers, and assessing best methods for differential diagnosis and prognosis. Much less of a focus was on young-onset dementia, mainly because it was so rare compared to late-onset dementia.
This paper by Hendriks and colleagues attempts to more accurately assess the prevalence of young-onset dementia across the world by incorporating 95 unique studies published to date. They demonstrate that, although still relatively rare, the prevalence is higher than previously estimated, even after excluding studies of specific ethnic populations and specific patient groups at high risk (e.g., HIV dementia, Down’s syndrome) or residents of care homes. Thus, the results are underestimates of the true prevalence of young-onset dementia.
This information is important for developing services and care for individuals and families affected, and for highlighting the fact that low- and middle-income countries will bear the biggest burden of young-onset dementia. An inherent next step is to better identify risk factors that contribute to young-onset dementia (genetic, sociocultural, and biological) that may help to explain some of the cross-country differences and could lead to potential interventions.
View all comments by Michelle MielkeThis paper, based on a comprehensive review of published papers that contain information about prevalence of dementia in persons younger than 65, and the accompanying editorial, provide good information about the relative frequency of dementia in younger persons. Compared with late-in-life dementia the frequency is dramatically less. I would classify it as rare and unusual, but nonetheless tragic. Younger persons will usually have longer duration of illness and perhaps a delay in diagnosis. The real public health burden of dementia is late-onset dementias, but those with earlier onset also benefit from good and ongoing care.
The prevalence seemed higher than I expected, but that’s because the sources are so different from real population-based and longitudinal data sources. What was most interesting was the different distributions of diagnoses—the editorial describe some variation [in diagnoses] based on demographics of people who attend the Mayo Clinic—and their geographic studies. The real value of this paper is for neurologists. It may not be that useful for planners or even public health researchers because there is so much variation in the [study] settings.
View all comments by Eric LarsonUCL Institute of Neurology
The greatest burden of dementia is found in the elderly, hence for clinicians, dementia, and thereby the diagnostic approach, is focused on diseases of the elderly such as Alzheimer’s disease and cerebrovascular disease.
Young-onset dementia (YOD), however, is not trivial and presents particular challenges for families involved. This systematic review and meta-analysis of the prevalence of YOD by Hendriks et al. provides a valuable reminder of the importance of this patient group and offers valuable data for health care planning.
Unsurprisingly, the published studies analyzed focused on the diagnoses we normally associate with late-life dementia, such as AD. Moreover, the authors excluded cohort specific studies such as those of HIV and trisomy 21. If our focus is broader and included the many diseases that can be associated with significant cognitive impairment, e.g., HIV, head trauma, etc. then the burden of young-onset disease is even greater.
View all comments by Martin RossorVA Boston Healthcare System
This article is an important reminder that dementia does not only affect older adults, but younger adults between the age of 30 and 64 as well.
Most individuals with young-onset dementia were between the ages 45 and 64; between ages 30 and 44 dementia was exceedingly rare. This suggests that clinicians should rarely diagnose a patient younger than age 44 with dementia, and then only with a positive biomarker or early onset genetic marker.
The most common young-onset dementia was Alzheimer’s disease (worldwide prevalence 41.1 per 100,000), which was more than twice as prevalent as vascular dementia (worldwide prevalence 14.9), and more than 17 times as prevalent as frontotemporal dementia (worldwide prevalence 2.3). This result was surprising because we generally think of the prevalence being equal between Alzheimer’s and frontotemporal dementia in individuals younger than age 65. However, the authors point out that frontotemporal dementia may have been misdiagnosed as another disorder given that pathology and biomarkers were rarely available.
View all comments by Andrew E. BudsonUniversity of New South Wales
The upper age limit of YOD remains disputed. Perhaps one should try to ascertain an empirical cut-off rather than using 65 years as an administrative one. A number of factors should go into this:
1. If one looks at the inflection point for prevalence estimates of dementia, perhaps 55 years is closer to where the inflection occurs.
2. Using 65 years makes the big three—AD, VaD, FTD—the major causes of both YOD and LOD, making the differentiation less meaningful.
3. If one considers the prevalence of AD, the inflection point is possibly later, and closer to 70 years. YOD is a tragic disease and has some unique characteristics. The definition should try to best capture this.
View all comments by Perminder SachdevMake a Comment
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