Page last updated at 23:52 GMT, Monday, 7 September 2009 00:52 UK

Infections 'speed memory loss'

Elderly man
Preventing common infections could stop memory loss

Infections outside the brain may speed memory decline in Alzheimer's disease, UK researchers say.

In a study of 222 elderly people with Alzheimer's they found that getting infections in places like the chest or urinary tract could double memory loss.

The Southampton University researchers think this leads to higher levels of an inflammatory protein called tumour necrosis factor (TNF) in the blood.

They say better care to prevent infections is very important.

Cognitive decline

The study published in the journal Neurology followed the Alzheimer's patients for six months.

Between them 110 of the 222 subjects developed a total of 150 infections, in areas such as the chest, stomach and intestines and the urinary tract, which led to the production of TNF proteins.

These are collectively known as acute systemic inflammation events (SIEs).

The worse the infection the worse the affect on the memory
Professor Clive Holmes, University of Southampton

Subjects with one or more SIEs during the six months follow-up had two times the rate of cognitive decline from their baseline score at the start of the study compared with those who had no SIE.

And those patients who had high baseline levels of TNF and then suffered an SIE over the following six months had a 10 fold increase in the rate of cognitive decline compared to those who were SIE free.

Further work

Professor Clive Holmes at the University of Southampton, who led the research, said they had looked at patients with mild, moderate and severe Alzheimer's disease.

"The worse the infection the worse the affect on the memory, but this is only an association at the moment.

'"One might guess that people with a more rapid rate of cognitive decline are more susceptible to infections or injury, but we found no evidence to suggest that people with more severe dementia were more likely to have infections or injuries at the beginning of the study.

It's important that older people, people with dementia and carers treat any infection seriously and seek medical help
Dr Susanne Sorensen, Alzheimer's Society

"If further work proves that TNF is causing more brain inflammation it may be possible to use drugs that block TNF to help dementia sufferers."

Professor Holmes said although common illnesses like colds and slight wounds could also set up an inflammatory response in the body, the data from his study did not support the idea that even these could cause memory loss.

Inflammatory processes

Dr Susanne Sorensen, Head of Research, Alzheimer's Society said: "This study is an important step towards understanding the processes that occur during the onset of Alzheimer's disease.

"We know there might be a link between inflammatory processes and Alzheimer's but this is not yet fully understood.

"These findings are helping us to understand more about possible reasons for this link.

"In the meantime it's important that older people, people with dementia and carers treat any infection seriously and seek medical help. "

Rebecca Wood, Chief Executive of the Alzheimer's Research Trust said: "This fascinating study shows that infections and inflammation may be linked to memory loss in Alzheimer's.

"We need to do more research into this and all aspects of the disease to understand its causes."

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