When Mr Lim, a retiree, forgot how to use the TV remote control and what he had for lunch, his family thought, "Oh, he's getting old." But soon, his memory started getting hazier. He forgot his grandchildren's names, and later his children's, although he could recollect childhood memories.

Then he began losing his way when driving, forgetting his way home; before long, he was asking his reflection in the mirror, "Who are you?" Meanwhile, his worsening dementia was accompanied by bouts of depression.
This connection between depression and dementia is something researchers have been looking at for some time now. Is there a link between the two? If so, which comes first? These questions are becoming more urgent, because dementia cases are on the rise both globally and locally.

Either dementia or depression can occur first

Professor Ranga Krishnan, formerly the Dean of Duke-NUS Graduate Medical School, explained that there is a vascular link between depression and dementia, and that either condition can occur first.

He said that in the last two decades, there have been about 200 studies on this subject. Retrospective investigations showed that many people who had depression later developed dementia. "It's the same illness showing up as dementia in one person and depression in another. Quite commonly, you see depression first and then dementia." He explained that silent strokes, multiple low-intensity strokes which people hardly notice and damaged nerves in the front of the brain can cause vascular depression. More extensive damage leads to vascular dementia. "When there is less damage, you get depression; more damage, you get dementia," Prof Ranga said.

He added that depression is vascular because psychiatric conditions are medical and involve the brain. "So, it's true when they say, 'It's all in your head!' All medical illnesses can lead to depression because of chemical changes in the brain. What is different is who treats them – psychiatrists, neurologists or general practitioners."

Causes of depression

There are many causes of depression. Vascular damage in the brain is one of them. Other causes, including stress, nutrition and possible genetic factors, also involve the brain. Other types of damage to the brain, such as frontotemporal dementia, can also lead to both depression and dementia.

Depression often manifests as sadness without reason, losing interest even in food, withdrawing, not going out, a change in sleep patterns, self-blame, a negative outlook, and feeling helpless, hopeless, worthless and suicidal.

Dementia manifests as a loss of short-term memory, although long-term memory remains intact. "It is akin to peeling an onion, with the outer layers (representing recent memory) coming off first. The bigger the onion, the longer it would take someone to peel it right to the core (long-term memory)."

Read on for the causes of dementia and how it can be prevented.

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