Patients who receive at least one influenza immunization over the course of their lives may be less likely to develop Alzheimer’s disease compared with those who are never vaccinated, according to research presented at the virtual Alzheimer’s Association International Conference in July.
Albert Amran, a fourth-year medical student at McGovern Medical School at the University of Texas Health Science Center at Houston, and colleagues analyzed data from 9,600 electronic medical records drawn from more than 600 hospitals and clinics. They found that compared with patients who had never received an influenza immunization, men who received one influenza immunization had a 27% lower likelihood of developing Alzheimer’s disease, and women had a 22% lower likelihood of developing Alzheimer’s disease. The researchers also found that influenza immunization was associated with a 28% lower likelihood in patients with diabetes.
Although the study was not designed to determine exactly how influenza immunization might lower risk, it may be that vaccination affects known risk factors for Alzheimer’s disease, such as chronic conditions that cause inflammation, Amran told Psychiatric News. This may be why vaccination appeared to lower Alzheimer’s risk in patients with diabetes, as diabetes is associated with inflammation, he added.
“Inflammation in the brain is thought to be a key player in the development of Alzheimer’s disease. The amyloid plaques that are the hallmark of this disease can induce neuroinflammatory responses themselves, and a strong immune reaction to these plaques is thought to drive cellular death,” Amran explained. “Controlling risk factors that are related to inflammation throughout the body is currently one of the focuses of research on how to prevent Alzheimer’s disease.”
Infections also cause inflammation, so avoiding the flu via immunization may help, Amran said.
“As people get older, the immune system is less able to control infection, which is what we’re currently seeing in the [COVID-19] pandemic with the virus affecting older people more than younger people,” Amran said. “Getting vaccinated may keep the immune system in shape.”
Amran said that further research is necessary, but in the meantime, patients should be counseled to get immunized.
“Although we can’t say that preventing Alzheimer’s is another reason to get a flu shot, it certainly won’t increase the risk,” Amran said. “Patients who haven’t gotten flu shots before should get one this year anyway. It’s more important than ever because of the pandemic.” ■
