Depression is an important risk factor of dementia

We can all feel down sometimes, but an unusually strong or enduring negative feeling can be a sign of depression.

Depression has a stigma and affects peoples’ self-esteem and self-judgement, which may affect who seeks help. People may think of their symptoms as a weakness that they don’t want to burden other people with.

Historically, depression is thought to have been under-reported for these reasons. However, clinical depression is an illness associated with changes in the brain.

We now know it to be one of Australia’s top health problems with more than a million Australians experiencing depression at any one time. In older adults, it is also an important risk factor for dementia.
 

Identifying depression
Everyone should know a little about identifying and addressing depression. Firstly, regardless of whether you experience depression yourself in your life, people close to you probably will.

Secondly, people may not recognise the signs in themselves, or be inclined not to mention it. Correctly addressing depression can greatly improve quality of life as the rates of recovery are good.

Alternatively, untreated depression is associated with a range of medical symptoms and raises the risk of other serious diseases.

Depression can start at any age or time. Factors such as social isolation and financial stress increase the risk of depression. Therefore, now more than ever, we should all be able to recognise the signs in ourselves and in those around us.

Identifying depression can be difficult and it is expressed differently in people. It always involves a persistent drop in your mood, with or without a clear cause.

People with depression may feel tired, want to sleep more and can lose their appetite and enjoyment in things. Others will be restless, irritable, unable to sleep properly or maintain their concentration. Some people notice a loss of mental function or stop wanting to be around others and some may feel they want to harm themselves.

Depression can often be harder to spot in others because some people get used to putting on a brave face to get through their day. Being male, older and living in a rural area are risk factors for not seeking help.
 

A link with dementia?
Epidemiological studies across the world have indicated that depression is an important risk factor for dementia. Most of an individual’s risk of dementia relates to their age and then inheritance of specific gene variations, factors which are not really modifiable.

Around about a third of dementia risk at a population level is related to what we refer to as potentially modifiable factors, of which depression is one. It has been estimated by the Lancet Commission on Dementia Prevention, Intervention and Care that depression accounts for approximately 4 per cent of total risk.

That is, if we were able to reduce depression completely in the community, there would be 4 per cent fewer people with dementia. That may not sound like much, but would correspond to around 2 million less cases of dementia around the world.

As with nearly every piece of medical research, there are important caveats in thinking about depression as a risk factor for dementia. Risk related to depression is probably more important when experienced later in life, than in early to mid-life. In addition, not all people who experience clinical depression will develop dementia, indeed, it would only be a small proportion.

Secondly, dementia itself can present with clinical features that mimic depression, so identifying the cause of a depressive state in an older person can be difficult.

Finally, while the population studies consistently identify a link between depression and dementia, we don’t yet know if alleviating depression, either medically or non-medically, prospectively reduces the risk.

Many studies are underway in this area, and so we hope to have a clear picture in the coming years of whether treating depression in older adults may reduce susceptibility to the cognitive changes associated with dementia.
 

Contributed by: The ISLAND Project
Wicking Dementia Research and Education centre

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