Both Diabetes and Depression Raise Risk of Dementia Interview with:
Dimitry S. Davydow, MD, MPH
Associate Professor
Department of Psychiatry and Behavioral Sciences
University of Washington School of Medicine
Seattle, WA 98195

Dr, Davydow wishes to acknowledge Dr. Wayne Katon, the lead investigator of the study, who passed away on March 1, 2015.

Medical Research: What is the background for this study?

Dr. Davydow: The medical and public health communities have known for quite a while that diabetes and depression are both potential risk factors for developing dementia later in life. Dr. Wayne Katon previously published two articles detailing the results of two studies of relatively large groups of patients (one with nearly 4,000 patients and the other with 29,000 patients) with diabetes showing that those with diabetes and co-existing depression had a greater risk of developing dementia later in life than those patients with just diabetes. These initial studies were important since patients with diabetes are 3 to 4-times more likely to suffer from depression compared to the general population.

However, it remained unclear when comparing to a population without either diabetes or depression, to what extent each independently raised the risk of developing dementia, and then to what extent having both conditions increased an individual’s subsequent risk of dementia. We sought to answer these questions with this study.

In addition, with the growing obesity epidemic, which carries with it higher burdens of both diabetes and depression, there is reason to be concerned that the risk of dementia could be higher at even younger ages. To address this issue, we also wanted to see if there was a differential impact of the combination of diabetes and co-existing depression on dementia risk among those younger than 65 compared to individuals 65 or older.

We were fortunate to be able to examine health data from all Danish citizens 50 or older over a 6 year period, a population numbering nearly 2.5 million people to be able to answer these questions.

Medical Research: What are the main findings?

Dr. Davydow: We found that compared to individuals without diabetes or depression, those with diabetes alone had about a 15% greater risk of developing dementia, those with depression alone had about an 83% greater risk of developing dementia, and those with both diabetes and co-existing depression had a 107% greater risk of developing dementia compared to those without either condition.

We also found that of all of the cases of dementia diagnosed in Denmark among individuals 50 or older between 2007 through 2013, 6% were potentially due to combination of having both diabetes and depression. This was also true for those 65 or older, where 6% of all diagnosed dementia was potentially attributable to the combination of both diabetes and depression. However, among individuals under age 65, we found that 25% of all cases of dementia may have been directly attributable to the combination of diabetes and co-existing depression.

Medical Research: What should clinicians and patients take away from your report?

Dr. Davydow: Our findings are very important for both patients and their health care providers. Arguably, the best treatment available for dementia is to prevent it from developing. If it turns out through future research that what we have found in our study documents a true, causal link between diabetes, depression and dementia, then there is the potential that successfully treating these illnesses could prevent future cases of dementia and improve quality of life for millions of individuals world-wide. Diabetes and depression are both diagnosable, and treatable conditions, and both can improve significantly with the right treatments. However, we don’t do a very good job of diagnosing either diabetes or depression early. Too frequently, diabetes isn’t found until patients have already had complications, and depression isn’t addressed until it is interfering with care for medical conditions, causing  problems with relationships and/or work/school, and/or resulting in suicide. Many studies have found that some interventions, based in primary care and other medical care settings, may lead to improved recognition and treatment of depression. One such study led by Dr. Wayne Katon, the TEAMcare study, which was published in the New England Journal of Medicine in 2010, found that a primary care-based intervention for patients with depression and either diabetes, high blood pressure, and/or elevated cholesterol not only reduced symptoms of depression but also improved blood pressure, cholesterol and blood glucose control. It remains to be seen whether interventions such as this one can prevent longer-term devastating consequences of these diseases, such as dementia.

Our results focusing on the risks for individuals under age 65 with both diabetes and depression are particularly concerning in light of the rates of obesity and associated chronic illnesses in the United States, and further highlight the need to improve recognition and treatment of medical conditions and co-existing psychiatric conditions, such as depression, in order to help prevent a potential tsunami of dementia over the next several decades.

Medical Research: What recommendations do you have for future research as a result of this study?

Dr. Davydow: Based on the results of our study, future research should seek to increase understanding of the biological mechanisms for how depression and diabetes may increase the risk of dementia, in order to develop potential treatments. For example, there is a fairly large body of research that has found that increased systemic inflammation may lead to cognitive impairment and decline, with elevated inflammation over time possibly increasing the risk of developing dementia. There have also been many studies that have found that during a depressive episode, patients have evidence of systemic inflammation, including elevated levels of cells regulating the body’s inflammatory response. One hypothesis is that increased inflammation could be a pathway by which depression, particularly repeated episodes of depression throughout life, may raise the risk of developing dementia later in life. We need additional research in this area.

In addition, we need more research examining whether existing interventions, such as the TEAMcare interventions or other similar programs, could ultimately prevent dementia, as well as the continued development of new interventions that can prevent the development of dementia.

Citation: Interview with: Dimitry S. Davydow, MD, MPH (2015). Both Diabetes and Depression Raise Risk of Dementia 

Last Updated on April 28, 2015 by Marie Benz MD FAAD