Diabetes combined with depression doubles the risk of dementia

If you are so unfortunate to both suffer from diabetes and depression, then your risk of also developing dementia increases by 117 per cent compared to a person who does not suffer from diabetes or depression.

This is shown by a major new registry study from the research group MEPRICA (Mental Health in Primary Care) at Aarhus University, who have for the first time examined the risk of developing dementia among people who suffer from both depression and diabetes.

The basis for the study is data from all Danes over the age of fifty, both ill and healthy, a total of 2,454,532 persons, of which almost 95,700 suffer from both depression and diabetes. The results have been published online in the scientific journal JAMA Psychiatry.

The risk is greater than expected

And the result has surprised the researchers:

"We already knew that diabetes and depression each increase the risk of developing dementia – by 20 per cent (diabetes) and 83 per cent (depression). But the combination of the two has been found to give a greater risk of dementia than we expected based on the level of risk for each disease individually. So the combination of the two is a dangerous cocktail," says PhD student and MD Anette Riisgaard Ribe from Aarhus University.

She adds that the new knowledge should primarily sharpen doctors' focus on this special group of patients:

"One obvious place to start would be to encourage people with depressive symptoms to go to their GP," she says.

Undertreatment of diabetes can play a role

Even though the researchers do not yet know what goes wrong, one hypothesis could be that patients suffering from depression do not have the necessary personal resources to take care of their diabetes and that it is therefore undertreated:

"We know that people with depression are more often undertreated in the healthcare system in cases where they also suffer from physical illnesses. If this also turns out to apply in connection with diabetes, then it may contribute to the increased risk of dementia that we have now found," says Anette Riisgaard Ribe.

She adds that future research can hopefully identify the factors which make the combination particularly dangerous and thus show the way towards new types of prevention and treatment.

Read the article "Effect of Depression and Diabetes Mellitus on the Risk of Dementia" in JAMA Psychiatry.

Facts:

• Dementia is experiencing rapid growth and currently affects 5-6 per cent of people over 60 years of age.
• The study was carried out in collaboration with researchers from the Department of Psychiatry and Behavioral Sciences, University of Washington, Seattle, USA.
• The study was financed by the Lundbeck Foundation.
• The data was taken from the following Danish national registers: The Danish Civil Registration System, the Danish National Diabetes Register, the Danish Psychiatric Central Register, the Danish National Patient Register and the Register of Medicinal Product Statistics.

Further information:

PhD student, MD Anette Riisgaard Ribe
Aarhus University, Department of Public Health and the Research Unit for General Practice
Tel.: +45 5092 8613
ar@feap.dk

Professor Mogens Vestergaard
Aarhus University, Department of Public Health and the Research Unit for General Practice
Tel.: +45 2343 9990
mv@ph.au.dk