Older people who require an anaesthetic are not at an increased risk of developing dementia, including Alzheimer's disease, a new study suggests.

According to US doctors, some elderly patients experience cognitive problems weeks or even months after a procedure that requires an anaesthetic. Because of this, there was concern that anaesthesia may play a role in long-term cognitive problems, such as dementia, in these patients.

Previous studies involving animals had suggested this was possible.

The doctors decided to investigate this further. They monitored around 900 dementia sufferers, all aged over 45, over a 10-year period and compared them to people without dementia.

The study found that a similar number - around seven in 10 people - from both groups underwent surgery that required general anaesthesia. Those that already had dementia did not experience a worsening of the condition after having an anaesthetic, while those without dementia did not go on to develop the condition.

"It's reassuring we're adding to the body of knowledge that there is not an association of anaesthesia and surgery with Alzheimer's. There are a lot of things to worry about when an elderly person has surgery, but it seems that developing Alzheimer's isn't one of them," the doctors said.

Details of these findings are published in the journal, Mayo Clinic Proceedings.

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