April 15, 2015

expert reaction to depression, diabetes and dementia

As depression and diabetes are individually thought to be risk factors for dementia, a team of researchers has investigated the effects of having both depression and diabetes. Publishing in JAMA Psychiatry, the researchers report that the risk of developing dementia is greater for people with both depression and diabetes than would be expected by simple addition of the individual risks for each disease.

Dr Doug Brown, Director of Research and Development at Alzheimer’s Society said:

“The more we learn about dementia the more we learn how other conditions may play a part in increasing risk of developing the condition. This study adds to a growing body of evidence that poorly managed type II diabetes and depression may increase risk and suggests that together, the two conditions could interact in a way that contributes to even greater risk. What’s not clear cut is why. This is a complex area that we need to see more research into so that we can fully understand this link and what this means for us all.

“This was a large and well conducted study looking at almost 2.4million people in Denmark which found that of the 59,663 people in the cohort who developed dementia, over a quarter had developed depression, ten per cent developed diabetes and nearly seven per cent developed both. Although insightful, we now need to take this observational study and investigate in more detail before we can draw firm conclusions.

“Research such as this can help improve public health policy, but we don’t want people with diabetes or living with depression to see this news and take it to mean that they’re going to develop dementia. If you’re concerned, contact your GP but in the meantime the best way to reduce risk of developing dementia is to eat a healthy balanced diet, take plenty of exercise, maintain a healthy weight and not smoke.”

Dr Tara Spires-Jones, Reader, Centre for Cognitive and Neural Systems, University of Edinburgh, said:

“This study of 2.4 million people highlights the need for more fundamental research into the relationships between depression, diabetes, and dementia.  While very interesting and important, this type of observational study does not prove that there is a direct link between these conditions and dementia. More studies will be needed to determine whether depression, diabetes, or the combination of the two are biologically important in causing dementia, or whether other related factors such as diet, genes, and healthy lifestyle are the culprits.

“A thorough understanding of the biology underpinning dementia is necessary for the development of effective therapeutics, and large studies such as this give us clues about important targets for further research.”

Dr Eric Karran, Director of Research at Alzheimer’s Research UK, the UK’s leading dementia research charity, said:

“This very large study adds weight to a body of evidence that has already linked type 2 diabetes and depression to an increased risk of dementia. Observational studies such as this are useful for highlighting health trends, but we can’t be sure whether other factors might have affected these results and this research doesn’t tell us that type 2 diabetes or depression cause dementia. The symptoms of dementia can overlap with symptoms of depression, with the early stages of dementia sometimes misdiagnosed as depression, and we don’t know whether this might have been the case for some of the people involved in this study. It’s also important to note that the percentage of people who developed dementia by the end of the study was small, even in the groups with the highest risk.

“Understanding the risk factors for dementia is important for gaining a clearer picture of how diseases that cause dementia develop, and for helping people to understand how to reduce their risk. We still need a better understanding of why conditions such as diabetes and depression might affect our risk of dementia, and investment in further research will be crucial to help answer this question. In the meantime, the best evidence suggests that we can help to reduce our risk of dementia by eating a healthy, balanced diet, exercising regularly, not smoking, drinking in moderation and keeping blood pressure and weight in check.”

‘Effect of Depression and Diabetes Mellitus on the Risk for Dementia: A National Population-Based Cohort Study’ by Katon et al. published in JAMA Psychiatry on Wednesday 15^th April. 

Declared interests

Dr Doug Brown: None declared

Dr Tara Spires-Jones: I am paid by the University of Edinburgh and am funded by Alzheimer’s Research UK, the University of Edinburgh and an anonymous foundation. I am on the Alzheimer’s Research UK Grants Advisory Board, am a member of the Journal of Neuroscience Editorial Board, and a member of SFN, FENS and BNA. I collaborate with Cognition Therapeutics, a pharmaceutical company in the US (not paid except occasional advisory board meeting compensation).

Dr Eric Karran: None declared