A new study on men living in Sweden suggests that a poor insulin response in midlife, the main characteristic of diabetes, is linked to an increased risk
of developing Alzheimer's disease up to 35 years later.
The study is published in the early online 9th April issue of Neurology and was conducted by Dr Elina Rönnemaa, from Uppsala University in Uppsala, Sweden, and colleagues.
Rönnemaa said the findings:
"Have important public health implications given the increasing numbers of people developing diabetes and the need for more powerful interventions."
For the longitudinal study, 2,269 men living in Sweden underwent glucose testing for diabetes in 1970, when they were enrolled in the Uppsala Longitudinal Study of Adult Men at age 50.
The results showed that:
- Men who had a low insulin response at age 50 (baseline) were nearly 1.5 times more likely to develop Alzheimer's disease than men who did not have insulin problems.
- The risk was still significant after adjusting for age, blood pressure, cholesterol, smoking, body mass index, insulin resistance and educational status.
- The link was stronger in those men who did not have the APOE4 gene, which is known to increase Alzheimer's risk.
- Impaired glucose tolerance increased the risk of vascular dementia but not Alzheimer's.
- Impaired insulin secretion, glucose intolerance, and estimates of insulin resistance, were all linked with elevated risk of any dementia and cognitive impairment.
"In this longitudinal study, impaired acute insulin response at midlife was associated with an increased risk of Alzheimer disease (AD) up to 35 years later suggesting a causal link between insulin metabolism and the pathogenesis of AD."
Rönnemaa said the results suggested:
"A link between insulin problems and the origins of Alzheimer's disease and emphasize the importance of insulin in normal brain function."
She explained that perhaps insulin problems lead to damaged blood vessels in the brain, which causes problems with memory and Alzheimer's disease, but she emphasized that further research was needed to discover the detailed underlying biology.
Rönnemaa pointed out that this finding shows that problems with insulin secretion are an important risk factor for Alzheimer's disease, when the genetic risk from the APOE4 gene is absent.
"Impaired insulin secretion increases the risk of disease."
E. Rönnemaa, B. Zethelius, J. Sundelöf, J. Sundström, M. Degerman-Gunnarsson, C. Berne, L. Lannfelt, and L. Kilander.
Neurology, first published online on 09 April 2008.
Click here for Abstract.
Source: Neurology abstract, American Academy of Neurology press release.
Written by: Catharine Paddock, PhD