Infections in Alzheimer's 'impact on memory'

Study links systemic inflammation to elevated levels of tumour necrosis factor alpha.

Respiratory and genitourinary infections may hasten memory loss in Alzheimer's disease, UK researchers believe.

Professor Clive Holmes and his colleagues at Southampton University looked at whether infection resulting in systemic inflammation affected rates of cognitive decline in Alzheimer's disease.

They assessed around 300 patients with the disease and found acute systemic inflammation occurred in around half of those studied. It was most frequently a result of respiratory or genitourinary infection.

Systemic inflammatory events were linked to a twofold increase in the rate of cognitive decline in these patients.

They were also associated with an increase in serum levels of the pro-inflammatory cytokine tumour necrosis factor alpha (TNF-alpha).

Patients whose mental faculties are declining faster do not seem to be more susceptible to infections, the researchers said.

'A plausible explanation of our observations is that, in Alzheimer's disease, acute systemic inflammation associated with increased TNF-alpha leads to increased cognitive decline, rather than systemic inflammatory events simply being a surrogate marker of disease progression,' they said.

They suggest that, because high TNF-alpha levels are associated with raised mortality, previous studies may have underestimated the effect of inflammation on cognition.

Dampening TNF-alpha levels following inflammation may prove beneficial in the treatment of Alzheimer's disease, they said.

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Neurology 2009; 73: 768-74.

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