Approximately Half of AD Dementia Cases are Mild, One-fifth are Severe

14 January 2021

Small amount of data on the severity of disease among people living with AD is currently available

Boston, MA, USA    What percent of patients with Alzheimer’s disease (AD) currently have severe dementia? Do more people have mild disease? Or are the majority suffering with moderate dementia? A new study published in the Journal of Alzheimer’s Disease using data from the Framingham Heart Study (FHS) sheds light on these trends.

Boston University School of Medicine researchers have found that slightly more than half (50.4 percent) of cases are mild, just under one-third (30.3 percent) of cases are moderate and 19.3 percent are severe cases. Among all participants with mild cognitive impairment (MCI) and AD, the pooled percentage was 45.2 percent for the combined group of mild AD dementia and MCI that later progressed to AD.

“Early intervention in MCI or the mild stage of AD dementia has been the primary focus for AD research and drug development in recent years. We found that approximately 45 percent of all those who are cognitively impaired or diagnosed with AD-dementia had early AD. Our results serve to inform the design of future research studies such as clinical and observational studies and provide optimal resource allocation for policy-making,” explained corresponding author Rhoda Au, PhD, professor of anatomy and neurobiology at Boston University School of Medicine.

To characterize the distribution of severity of AD dementia and MCI among prevalent cases in the population, FHS participants (aged 5094) with prevalent MCI or AD dementia clinical syndrome were selected from three time-windows: 20042005, 20062007 and 20082009. Estimates of the severity distribution were achieved by pooling results across time-windows. Diagnosis and severity were assessed by consensus dementia review. MCI-progressive was determined if the participant had documented progression to AD dementia clinical syndrome using longitudinal data.

According to the researchers the finding that half of the people living with AD have mild disease underscores the need for research and interventions to slow decline or prevent progression of this burdensome disease. “It is crucial to determine risk factors or develop therapies that could alter the disease trajectory to improve individuals’ quality of life and alleviate the socio-economic burden,” adds Au.

The researchers believe that most people who have AD are still at a stage when there is still some preserved quality of life. “This means any drug treatment that is effective might help prevent their AD from getting worst.”



Full Article: "Severity Distribution of Alzheimer's Disease Dementia and Mild Cognitive Impairment in the Framingham Heart Study" by J Yuan, N Maserejian, Y Liu, S Devine, C Gillis, J Massaro, and R Au (DOI: 10.3233/JAD-200786, published online in the Journal of Alzheimers Disease, ahead of the publication of Volume 79, Issue 2 (2021). The article can be viewed online at:

Funding for this study was provided his work was supported by the Framingham Heart Study’s National Heart, Lung, and Blood Institute contract (N01-HC-25195; HHSN268201500001I), and NIH grants from the National Institute on Aging (AG008122, AG016495, AG033040, AG054156, AG049810, AG062109), and Pfizer; Analytic support was provided by Biogen.

Media contact: Gina DiGravio, Boston University (+1 617-224-8962 or

About the Journal of Alzheimer's Disease 
Now in its 24th year of publication, the Journal of Alzheimer's Disease (JAD) is an international multidisciplinary journal to facilitate progress in understanding the etiology, pathogenesis, epidemiology, genetics, behavior, treatment, and psychology of Alzheimer's disease. The journal publishes research reports, reviews, short communications, book reviews, and letters-to-the-editor. Groundbreaking research that has appeared in the journal includes novel therapeutic targets, mechanisms of disease, and clinical trial outcomes. JAD has a 2019 Journal Impact Factor of 3.909 according to Journal Citation Reports (Clarivate, 2020). It is published by IOS Press.