Catching a cold, flu or stomach bug could speed memory loss in people with Alzheimer's disease, suggests a study in the journal Neurology.
Researchers found that among patients with Alzheimer's disease, those who had suffered sudden or chronic infections, or even bruises from a fall, were much more likely to experience faster memory loss than people who did not have infections.
The researchers, from Britain's University of Southampton, think the reason for the difference may be traced to a protein involved in inflammation. There appears to be a link between inflammatory processes and Alzheimer's, though the link is not yet fully understood.
Those patients who had battled a chronic or sudden infection had high blood levels of tumor necrosis factor-alpha, a protein involved in the inflammatory process/
A team led by Dr. Clive Holmes measured the memory abilities of 222 people with Alzheimer's disease with an average age of 83. They also measured their blood levels of TNF-alpha.
Over the next six months, caregivers for roughly half the group reported their patients had experienced a sudden infection or injury that led to inflammation and a spike in TNF-alpha levels. Those who had become ill experienced memory loss that was at twice the rate of those who did not have infections or injuries, ther researchers found.
Patients who had high levels of the protein in their blood at the beginning of the study, which may indicate chronic inflammation, had memory loss at four times the rate of those with low levels of the protein at the start of the study.
Those who had high levels of the protein at the start of the study who also experienced acute infections during the study had memory loss at 10 times the rate of those who started with low levels and had no infections over the six-month period.
In contrast, those who had low levels of serum TNF-alpha throughout the study showed no cognitive decline over the six-month period.
Dr. Susanne Sorensen, head of research at Britain's Alzheimer's Society, which funded the research, said the study is an important step towards understanding the processes that occur during the onset of Alzheimer's disease.
Holmes said more research is needed to understand the role of TNF-alpha in the brain, but it's possible that finding a way to reduce levels of the protein could benefit Alzheimer's disease patients.
