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T. Kawada


Department of Hygiene and Public Health, Nippon Medical School

Corresponding Author: Tomoyuki Kawada, Department of Hygiene and Public Health, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-Ku, Tokyo 113-8602, Japan,

J Prev Alz Dis 2022;
Published online April 28, 2022,


I read the paper by Wang et al. with great interest (1). The authors conducted a prospective study to evaluate the effect of early-onset type 2 diabetes (T2DM) on the risk of all dementia, Alzheimer Disease (AD) dementia and stroke. The adjusted hazard ratios (95% confidence intervals [CIs]) of patients with early-onset T2DN under 55 years of age for all dementia, Alzheimer disease dementia and stroke were 2.86 (1.16-5.51), 2.42 (1.63-4.33), and 2.85 (1.37-3.98), respectively. In contrast, there was no significant risk of all dementia and Alzheimer disease dementia in patients with T2DM, who were 55 or older. I present some information about their study.
First, Barbiellini Amidei et al. conducted a prospective study with a median follow-up of 31.7 years (2). The adjusted HRs (95% CI) of participants with T2DM onset >10 years, 6 to 10 years, and ≤5 years for dementia were 2.12 (1.50-3.00), 1.49 (0.95-2.32), and 1.11 (0.70-1.76), respectively. Risk of dementia after T2DM onset was not observed within 10 years, and the gradient of dementia risk against the time of T2DM onset became smaller in older population. They also observed that younger age at T2DM onset, especially in patients aged 55 years, presented steeper gradient for the incidence of dementia by following-up. Although this report did not specify the type of dementia as clinical outcomes, simultaneous cardiovascular comorbidities of stroke, coronary heart disease and heart failure contributed to the increased risk of dementia, presenting HR (95% CI) of 4.99 (2.19-11.37). They used stroke events as an independent variable for predicting dementia. As stroke is a cause of dementia, prediction model should be made with caution.
Second, Reinke et al. conducted a prospective study to investigate the effect of T2DM duration on the risk of dementia, and there was a U-shaped dementia risk over time (3). After T2DM diagnosis the dementia risk decreased and reached a minimum at 4.75 years, followed by an increase through the end of follow-up. They included T2DM complications at the time of T2DM diagnosis for the analysis, and new onset of comorbidities during the follow-up may also contribute to the subsequent risk of dementia.
Anyway, further study is needed to speculate the mechanism of the association between T2DM onset and subsequent risk of all dementia and AD dementia.


Conflict of interest: None declared.



1. Wang K, Liu H. Early-onset subgroup of type 2 diabetes and risk of dementia, Alzheimer’s disease and stroke: A cohort study. J Prev Alzheimers Dis 2021;8(4):442-447; doi: 10.14283/jpad.2021.35..
2. Barbiellini Amidei C, Fayosse A, Dumurgier J, et al. Association between age at diabetes onset and subsequent risk of dementia. JAMA 2021;325(16):1640-1649; doi: 10.1001/jama.2021.4001..
3. Reinke C, Buchmann N, Fink A, Tet al. Diabetes duration and the risk of dementia: a cohort study based on German health claims data. Age Ageing 2022;51(1):afab231; doi: 10.1093/ageing/afab231.