Flu, pneumonia vaccinations may reduce risk for Alzheimer’s disease
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Flu and pneumonia vaccines appeared linked to reduced risk for Alzheimer’s disease, according to data presented at the Alzheimer’s Association International Conference 2020.
“With the COVID-19 pandemic, vaccines are at the forefront of public health discussions,” Maria C. Carrillo, PhD, chief science officer of the Alzheimer’s Association, said in a press release. “It is important to explore their benefit in not only protecting against viral or bacterial infection but also improving long-term health outcomes.
“It may turn out to be as simple as if you’re taking care of your health in this way — getting vaccinated — you’re also taking care of yourself in other ways, and these things add up to lower risk of Alzheimer’s and other dementias,” Carrillo added. “This research, while early, calls for further studies in large, diverse clinical trials to inform whether vaccinations as a public health strategy decrease our risk for developing dementia as we age.”
Results of three studies supported the association between these vaccinations and reduce risk for Alzheimer’s disease.
Reduced Alzheimer’s disease incidence from seasonal flu vaccine
No large, comprehensive studies have previously evaluated the relationship between flu vaccines and Alzheimer’s disease, despite some evidence showing suggested vaccinations may protect against cognitive decline. Albert Amran, a fourth-year medical student at McGovern Medical School at the University of Texas Health Science Center at Houston, and colleagues aimed to address this research gap by analyzing data of 9,066 patients included in a large American health record dataset.
Results showed one flu vaccination was linked to a lower prevalence of Alzheimer’s disease. Individuals who consistently received an annual flu shot exhibited a lower risk for Alzheimer’s disease, with a nearly 6% reduction among those aged 75 years to 84 years.
Those who received their first flu vaccine at a younger age exhibited a stronger protective association.
“Our study suggests that regular use of a very accessible and relatively cheap intervention — the flu shot — may significantly reduce risk of Alzheimer’s dementia,” Amran said in a press release. “More research is needed to explore the biological mechanism for this effect — why and how it works in the body — which is important as we explore effective preventive therapies for Alzheimer’s.”
Pneumonia vaccine associated with late-life Alzheimer’s disease risk reduction
Svetlana Ukraintseva, PhD, associate research professor of the Biodemography of Aging Research Unit at Duke University Social Science Research Institute, and colleagues evaluated associations between risk for Alzheimer’s disease and pneumococcal vaccination, with and without an accompanying seasonal flu shot, and accounted for the role of a specific G allele known to be a risk factor.
“Very different pathogens (viral, bacterial, fungal) have been linked to Alzheimer’s disease during the past decade of research, which indicates a possibility that compromised host immunity may play a role in it through increasing overall brain vulnerability to various microbes,” Ukraintseva told Healio Psychiatry. “Vaccinations against pneumonia and the flu showed beneficial ‘off-target’ effects, including on dementia-related outcomes, in some studies.
“One reason for this could be that such vaccines may potentially improve host immunity on a broad scale,” Janbek added. “If so, they might be reasonable candidates for repurposing for prevention of various disorders, in which vulnerability to infections may play a role, including Alzheimer’s disease.”
They included participants 65 years and older who were included in the Cardiovascular Health Study,
Results showed an association between pneumococcal vaccination between ages 65 years and 75 years and a reduced risk for developing Alzheimer’s disease by 25% to 30%, after adjusting for race, birth cohort, education, sex, smoking and number of G alleles. Individuals who were vaccinated against pneumonia who were also non-carriers of the risk gene exhibited the largest risk reduction, which was up to 40%. Further, total number of vaccinations against the flu and pneumonia between ages 65 years and 75 years was also linked to a lower risk for Alzheimer’s disease; however, the flu shot alone did not appear to produce this effect.
“Results of our study suggest that adult pneumococcal vaccine may reduce Alzheimer's disease risk depending on individual genotype, which supports its further investigation as a candidate for repurposing in personalized Alzheimer's disease prevention,” Ukraintseva said in the release. “These results also support a possibility of boosting the immune robustness/resilience for preventing Alzheimer’s disease..”
Viral, bacterial, other infections increase mortality among those with dementia
Viral, bacterial and other infections commonly occur among individuals with dementia, and researchers have begun to more closely examine whether infections may be worsening or potentially causing dementia.
Janet Janbek, a PhD student of the Danish Dementia Research Centre at the University of Copenhagen in Denmark, and colleagues investigated mortality among 1,496,436 Danish residents older than 65 years who were included in national health registries for hospital visit with an infection.
"We know from previous studies that pneumonia and sepsis infections are linked to higher mortality risk among people with dementia," Janbek told Healio Psychiatry. "We don’t know how these infections compare with other infection types and whether mortality risk is also higher for other infections, such as an ear or eye infection, among people with dementia. We also don’t know a lot about the long-term mortality risk."
Results showed a 6.5 times higher mortality rate among those with both dementia and such hospital visits vs. those who had neither. Moreover, participants with either dementia alone or infect-relation contacts alone exhibited a rate that was threefold higher. The mortality rate was highest within the first 30 days after the hospital visit.
Janbek and colleagues also reported that among those with dementia, mortality rates were elevated for 10 years after the initial infection-related hospital visit. Mortality rates from all infections among this population were higher than those of people without dementia or an infection-related hospital visit.
"A more specialized clinical attention needs to be given to people with dementia following any type of infection because they may lack the appropriate medical care after discharge from the hospital," Janbek told Healio Psychiatry. "We need to further our understanding of the possible patient and health care factors that contribute to the increased mortality. Identifying these makes it possible to develop targeted interventions and approaches towards better clinical care that can ensure better overall health for people living with dementia and limit adverse outcomes on their short- and long-term health.
"We also know that infections can be avoidable, and from our study we now know more about their serious consequences among people with dementia," Janbek added. "It could therefore be of benefit to explore possible preventive measures in this particularly vulnerable group."