Severity Distribution of Alzheimer’s Disease Dementia and Mild Cognitive Impairment in the Framingham Heart Study

Article type: Research Article

Authors: Yuan, Jing^{a; b; 1} | Maserejian, Nancy^{c; 1} | Liu, Yulin^{b; d} | Devine, Sherral^{b; d} | Gillis, Cai^c | Massaro, Joseph^{d; e} | Au, Rhoda^{b; d; f; g; *}

Affiliations: [a] Department of Neurology, Peking Union Medical College Hospital, Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing, People’s Republic of China | [b] Department of Anatomy and Neurobiology, Boston University School of Medicine, Boston, MA, USA | [c] Department of Epidemiology, Biogen, Cambridge, MA, USA | [d] Framingham Heart Study, Boston University School of Medicine, Boston, MA, USA | [e] Biostatistics Department, Boston University School of Public Health, Boston, MA, USA | [f] Department of Neurology, Boston University School of Medicine, Boston, MA, USA | [g] Department of Epidemiology, Boston University School of Public Health, Boston, MA, USA

Correspondence: [*] Correspondence to: Rhoda Au, PhD, 72 E. Concord Street, R10, Boston, MA 02118, USA. Tel.: +1 617 638 8067; Fax: +1 617 638 8086; E-mail: rhodaau@bu.edu.

Note: [1] These authors contributed equally to this work.

Abstract: Background:Studies providing Alzheimer’s disease (AD) prevalence data have largely neglected to characterize the proportion of AD that is mild, moderate, or severe. Estimates of the severity distribution along the AD continuum, including the mild cognitive impairment (MCI) stage, are important to plan research and allocate future resources, particularly resources targeted at particular stages of disease. Objective:To characterize the distribution of severity of AD dementia and MCI among prevalent cases in the population-based Framingham Heart Study. Methods:Participants (aged 50–94) with prevalent MCI or AD dementia clinical syndrome were cross-sectionally selected from three time-windows of the population-based Framingham Heart Study in 2004-2005 (n = 381), 2006-2007 (n = 422), and 2008-2009 (n = 389). Summary 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. Results:Among AD dementia participants, the pooled percentages were 50.4%for mild, 30.3%for moderate, and 19.3%for severe. Among all MCI and AD participants, the pooled percentages were 29.5%, 19.6%, 25.7%, and 45.2%for MCI-not-progressive, MCI-progressive, mild AD dementia, and the combined group of MCI-progressive and mild AD dementia, respectively. Distributions by age and sex were presented. Conclusion: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.

Keywords: Alzheimer’s disease, dementia, epidemiological study, epidemiology, Framingham Heart Study, mild cognitive impairment, prevalence

DOI: 10.3233/JAD-200786

Journal: Journal of Alzheimer's Disease, vol. 79, no. 2, pp. 807-817, 2021