Compared with a nondiabetic control population, those with type 2 diabetes had a statistically significant 35% increased chance of having vascular dementia in a large observational study.
By comparison, the risk for nonvascular dementia was increased by a "more modest" 8%, said the researchers from the University of Glasgow and the University of Gothenburg (Sweden), while the risk for Alzheimer's dementia appeared to be reduced by 8%.
The link between type 2 diabetes and dementia is not new, observed Carlos Celis-Morales, PhD, who presented the study's findings at the virtual annual meeting of the European Association for the Study of Diabetes. With people living longer thanks to improved preventative strategies and treatments, there is a risk for developing other chronic conditions, such as dementia.
"A third of all dementia cases may be attributable to modifiable risk factors, among them type 2 diabetes, which accounts for 3.2% of all dementia cases," said Dr. Celis-Morales, a research fellow at the University of Glasgow's Institute of Cardiovascular and Medical Sciences.
"Although we know that diabetes is linked to dementia, what we don't know really well is how much of this association between diabetes and dementia outcomes are explained by modifiable and nonmodifiable risk factors," Dr. Celis-Morales added.
"Diabetes and dementia share certain risk factors," commented coinvestigator Naveed Sattar, MD, in a press release issued by the EASD. These include obesity, smoking, and lack of physical activity and might explain part of the association between the two conditions.
Dr. Sattar said that the heightened vascular dementia risk found in the study was "in itself an argument for preventive measures such as healthier lifestyle," adding that "the importance of prevention is underscored by the fact that, for the majority of dementia diseases, there is no good treatment."
Using data from the Swedish National Diabetes Register NDR, the research team set out to determine the extent to which type 2 diabetes was associated with dementia and the incidence of different subtypes of dementia. They also looked to see if there were any associations with blood glucose control and what risk factors may be involved.
In total, data on 378,299 individuals with type 2 diabetes were compared with data on 1,886,022 similarly aged (average, 64 years) and gender-matched controls from the general population.
After a mean 7 years of follow-up, 10,143 people with and 46,479 people without type 2 diabetes developed dementia. Nonvascular dementia was the most common type of dementia recorded, followed by Alzheimer's diseaseand then vascular dementia.
"Within type 2 diabetes individuals, poor glycemic [control] increased the risk of dementia especially for vascular dementia and nonvascular dementia. However, these associations were not as evident for Alzheimer's disease," Dr. Celis-Morales reported.
Comparing those with hemoglobin bA1c of less than 52 mmol/mol (7%) with those whose A1c was above 87 mmol/mol (10.1%), there was a 93% increase in the risk for vascular dementia, a 67% increase in the risk for nonvascular dementia, and a 34% higher risk for Alzheimer's disease-associated dementia.
"We have focused on high levels of HbA1c, but what happens if you have really low limits? It's something we're working on right now," Dr. Celis-Morales said.
Importantly, cardiovascular-related risk factors – some of which, like systolic blood pressure and body weight, were potentially modifiable – accounted for more than 40% of the risk for dementia in type 2 diabetes. This suggests that a large percentage of the dementia risk could perhaps be addressed by identifying high-risk individuals and tailoring interventions accordingly.
"These are observational findings, so we need to be careful before we translate to any sort of recommendation," Dr. Celis-Morales said.
The study was financed by the Swedish state under the agreement between the government and the county councils, the ALF agreement, as well as grant from the Novo Nordisk Foundation and the Swedish Association of Local Authorities and Regions. Dr. Celis-Morales and Dr. Sattar had no conflicts of interest.
SOURCE: Celis-Morales C et al. EASD 2020, Oral presentation 06.
C. Celis-Morales1, S. Franzén2, A.-M. Svensson3, N. Sattar1, S. Gudbjornsdottir2;
1Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, UK, 2Department of Molecular and Clinical Medicine, University of Gothenburg, Gothenburg, Sweden, 3Swedish National Diabetes Register, Gothenburg, Sweden.
Background and aims:
Type 2 diabetes (T2D) has been associated with high dementia risk. However, the links to different dementia sub-types is unclear. We examined to what extent T2D associated with Alzheimer, vascular and non- vascular dementia incidence and whether such associations differed by glycaemic control.
Materials and methods:
In this Swedish National Diabetes Register study, we included 378,299 patients with T2D and 1,886,022 matched controls. The outcomes were incidence of Alzheimer, vascular and non- vascular dementia. The association of T2D with dementia was stratified by baseline Glycated Haemoglobin (HbA1c) concentrations. Cox regression was used to study the excess risk of outcomes.
The follow-up (median 6.8 years) 21,651 (5.7%) T2D patients and 98,723 (5.2%) controls developed dementia. The strongest association was observed for vascular dementia: here, patients with T2D had a HR of 1.36 [95% CI 1.03, 1.09] compared to controls. The association of T2D with non-vascular dementia was more modest (HR: 1.08 [95% CI 1.04, 1.12]). However, risk of Alzheimer was lower in T2D patients compared to controls (HR: 0.92 [95% CI 0.87, 0.98]). When the analyses were stratified by circulating concentrations of HbA1c a dose-response association was observed. Compare to patients with T2D with HbA1c <52 mmol/mol, those with HbA1c >87 mmol/mol had a higher risk of Alzheimer (HR: 1.34 [95% IC 1.03, 1.75]), vascular dementia (HR: 1.93 [95% IC 1.53, 2.42]) and non-vascular dementia (HR: 1.67 [95% IC 1.45, 1.91]). When a 3-years landmark analysis was conducted, the associations remained similar for vascular and non-vascular dementia but disappeared for Alzheimer’s diseases.
The association of T2D with neurodegenerative diseases differ by type of dementia. The strongest detrimental association was observed for vascular dementia. Moreover, T2D patients with poor glycaemic control have an increased risk of developing vascular and non-vascular dementia.
www red DiabetologNytt