Flu, Alzheimer's Have Similar Patterns But No Apparent Relationship

Alzheimer’s disease, a neurological disorder expected to more than triple in incidence by 2051, has some interesting similarities with infections like the flu.

Drug developments related to the “amyloid hypothesis” have failed to produce clinically effective drugs, but neuroinflammation is an emerging pathogenesis candidate for Alzheimer’s disease.

Researchers have previously found the following similarities between Alzheimer’s and the flu:

· Mental status changes, including confusion, delirium, convulsions, and encephalopathy.

· Neuropsychiatric disorders later in life among pregnant patients' unborn babies.

· An immune response in the hippocampal regions of mice that kills cells in a manner reminiscent of Alzheimer’s.

Might a study of the relationship between influenza and Alzheimer’s be in order?

An article published ahead-of-print in Brain, Behavior, and Immunity indicated that there is no association between influenza infection and the risk of Alzheimer’s disease development. The authors used data from the Clinical Practice Research Datalink, which includes 10 million primary care patients, for their analysis.

They assessed patients diagnosed with Alzheimer’s, any unspecified dementia, or first prescriptions for acetylcholinesterase inhibitors between January 1998 and July 2013 for past influenza.

Neither the severity nor the number of influenza infections were associated with increased risk of Alzheimer’s.

More than 90% of patients with Alzheimer’s had no history of influenza infection, and only 1% had multiple infections in the database’s lifetime. Less than 1% of patients with Alzheimer’s had a history of neurological complications during a past influenza infection.

Comorbid chronic inflammatory disorders were not associated with increased risk of Alzheimer’s, either.

A previous study found no relationship between influenza and Alzheimer’s, but it did suggest that influenza may exacerbate Alzheimer’s and that other viruses may also have an impact.

A lack of universal viral testing limited the ability to confirm influenza diagnoses. In addition, it is possible that Alzheimer’s may be tied to influenza infections farther in the past than what was available in the digital record.