Depression 'may increase risk of developing dementia'

The findings, from an American study, reinforce claims of a link

between depression and dementia.

Scientists are not sure why such an association might exist, but believe brain inflammation, the action of certain proteins, and lifestyle factors may play a role.

The latest research involved almost 1,000 people with an average age of 79 who had been enrolled into a large US heart study.

At the beginning, all were free of dementia. Psychological tests identified 125, or 13 per cent, of the study participants, were classified as being depressed.

By the end of the 17-year study, 164 of the recruits had dementia, of whom 136 were diagnosed with Alzheimer's.

Nearly 22 per cent of those who were depressed at the outset developed dementia compared with 16.6 per cent of those free from depression. They were around 30 per cent more likely to acquire a dementia illness.

The results, published yesterday in the journal Neurology, were unaffected by a person's age, sex, education, or possession of the defective APOE gene that is known to increase the risk of Alzheimer's disease.

Leading researcher Dr Jane Saczynski, from the University of Massachusetts Medical School in Worcester, US, said: "While it's unclear if depression causes dementia, there are a number of ways depression might impact the risk of dementia.

"Inflammation of brain tissue that occurs when a person is depressed might contribute to dementia. Certain proteins found in the brain that increase with depression may also increase the risk of developing dementia.

"In addition, several lifestyle factors related to long-term depression, such as diet and the amount of exercise and social time a person engages in, could also affect whether they develop dementia."

Previous studies have also suggested a link between depression and dementia, but their results have been inconsistent.

An estimated 750,000 Britons have some form of dementia, with more than half suffering from Alzheimer's.

A million people are expected to be living with dementia in 15 years time, and by 2051 the figure is expected to soar to 1.7 million.

Professor Clive Ballard, director of research at the Alzheimer's Society, said: "This is a large and robust study that adds considerable weight to the accumulating evidence of a link between depression and dementia.

"However, more research is now needed to establish why the link exists."