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Infections Linked to Mental Decline in Alzheimer's Disease

Patients with Alzheimer's who had acute systemic inflammation had higher rate of cognitive decline

WEDNESDAY, Sept. 9 (HealthDay News) -- Acute systemic inflammation linked to episodes of illness or injury may speed the rate of cognitive decline in individuals with Alzheimer's disease, according to research published in the Sept. 8 issue of Neurology.

Clive Holmes, Ph.D., of the University of Southampton in the United Kingdom, and colleagues analyzed data from 275 patients with mild to severe Alzheimer's disease (mean age, 82.7 years). Subjects underwent cognitive assessment and blood testing at baseline and two, four and six months, and caregivers provided information on recent systemic inflammatory events (including respiratory, gastrointestinal or other infections, and minor injury from falls) that occurred in the subjects.

The researchers found that higher baseline levels of tumor necrosis factor α (TNF-α) were associated with a four-fold increase in the rate of cognitive decline during six months of follow-up. During follow-up, about half of subjects had acute systemic inflammatory events, which were associated with a rise in TNF-α and a two-fold increase in the rate of cognitive decline over six months.

"In keeping with other studies, high TNF-α levels in this study were associated with increased mortality. This may have led to an underestimate of the cognitive effects of TNF-α on cognitive decline," the authors write. "The role of TNF-α within the brain is controversial, with evidence supportive of both deleterious and protective effects. However, if systemic inflammation has different central nervous system consequences depending on the existing relative activation state of the central innate immune system, dampening down systemic TNF-α may prove to be beneficial in Alzheimer's disease."

Several co-authors reported financial relationships with a pharmaceutical company and a variety of associations and research councils.

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