Is there a relationship between diabetes and dementia? Are people with diabetes more at risk of developing Alzheimer’s disease than others? Why? These questions concern as much as 11% of adults in the US.
What is diabetes?
Diabetes is a lifelong disease in which levels of sugar in the blood are high. When food is digested, a sugar called glucose is moved to the blood stream. Glucose is a source of energy for the body. Insulin is a hormone that controls blood sugar by moving glucose from the bloodstream into muscle, fat, and liver cells, where it can be used as fuel. Diabetes is triggered when too little insulin is produced by the body or when the cells do not respond normally to insulin. The consequence is that too much glucose stay in the bloodstream.
A link between Alzheimer’s and diabetes
A very thorough analysis was recently published by a group of Japanese researchers. They followed over 1,000 adults for 15 years. All the participants were dementia-free at the beginning of the study. All agreed to take a glucose tolerance test to detect diabetes. Over the 15 years, 232 participants developed dementia.
The study showed that 27 percent of those with diabetes developed dementia, compared to 20 percent of people with normal blood sugar levels. This was true even when other risk factors were taken into consideration. The study also showed that pre-diabetes — higher than normal blood sugar levels — also raised the risk of dementia.
Alzheimer’s was the most common type of dementia diagnosed in the study. Participants with diabetes had slightly more than double the odds of developing Alzheimer’s compared to participants without diabetes.
Vascular dementia (which is caused by several strokes, causing impaired blood flow) was another type of dementia diagnosed in the study. An increased risk for vascular dementia was found for participants with diabetes. However the link disappeared when other lifestyle factors were taken into consideration (such as drinking, smoking and exercise).
How does it work?
There is no clear answer to this question. Diabetes could be connected to dementia because it contributes to vascular disease, disrupting the flow of oxygen to the brain. More research is needed to better understand the link between diabetes and dementia. Note also that we are talking about an association between the two which does not imply causation: Other factors could be responsible for the link.
Read about factors that may decrease risks of dementia:
- The Mediterranean Diet Lowers Risks of Cognitive Decline
- A Drink a Day can Decrease Risk of Memory Loss
Ohara, T. et al. (2011). Glucose tolerance status and risk of dementia in the community. The Hisayama study. Neurology, 77, 1126-1134.