Depression and dementia risk

It is not widely recognised that depression increases the risk of late-life dementia.

Written by Kaarin Anstey

Recently, long-term studies have shown that adults who experienced mid-life depression were 20% more likely to develop dementia in late life than adults who did not experience mid-life depression.

Depression is common - in fact one in five adults will experience depression at some stage in their life. This means that all of us will know family members and friends with depression, or experience it ourselves.

Among older adults, the symptoms of depression are sometimes confused with other health problems. As well as depressed mood, depression may also involve problems with sleep, tiredness, lack of motivation and irritability. A person must have these symptoms for more than two weeks to be diagnosed with depression.

In late-life, it is common for symptoms of depression to accompany a decline in cognitive function and memory. This may be in part a reaction to the awareness that one is deteriorating cognitively. It is also thought that for some people, depressed mood is directly linked to the brain changes that cause dementia, particularly vascular changes.

Why? No one really understands the mechanisms fully. Genetics and other biological factors are important causes of Alzheimer’s disease and dementia, and it is likely that risk factors such as depression interact with these. Depression is associated with cardiovascular disease (both as a risk factor and consequence) and heart health is strongly linked with brain health. Depression is associated with increased inflammation, which in turn is associated with brain ageing and Alzheimer’s disease. Also, It is more difficult for us to maintain a healthy lifestyle while we are feeling sad or down, and more difficult to feel motivated to see friends, exercise and eat well. Depression may also lead to increased stress hormones and these may affect parts of the brain that are vulnerable in dementia.

So what can we do?

First, make lifestyle changes that may help reduce depressive symptoms and reduce the impact of depression on your life. There is now good evidence that physical activity reduces depressive symptoms and some dietary patterns increase your risk of poor mood. Remaining socially engaged by seeing friends and family and participating in sports and social activities you enjoy is also important for brain health. These things may be difficult to maintain when people are depressed. So it is important to consider whether feeling down is reducing other activities in your life that are important for brain health and that may improve your mood.

Second, if you think you might be depressed, seek help and become informed - effective treatments include talking therapies, online therapies, and medication. Information on types of help available and practical advice on lifestyle can be found at beyondblue.org.au.

Written by Kaarin Anstey

Director of the Centre of Research on Ageing, Health and Wellbeing at the Australian National University Professor Anstey's research interests include prevention of cognitive decline and dementia, mental health and strategies to optimise ageing well.

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