Does Flu Vaccination Reduce Dementia Risk?

In my daily review of neuroscience news I ran across an article flu vaccination and dementia risk in heart failure.

This study was reported at the 3rd World Congress on Acute Heart Failure by Dr. Ju-Chi Liu from Taipei Medical University.

So how might influenza vaccination be related to dementia risk?  We do know acute influenza infection reaches the brain causing headache and increasing brain inflammation, at least temporarily. We also know brain inflammation may be involved in the mechanism of amyloid and tau protein deposition in the brain. So this link has some potential biological plausibility.

In the Taiwanese study, 20,509 subjects with a diagnosis of heart failure were followed via centralized records. About half received flu vaccination during follow up. Subjects receiving at least one flu vaccination had a 35% lower rate of dementia diagnosis compared to those not receiving any vaccination. Subjects receiving three or more vaccinations had a 55% lower risk of recorded dementia diagnosis on follow up.

I went to PubMed looking for more research for this association and a similar finding has been published by the same research group in a free full-text manuscript in patients with chronic kidney disease (CKD). The key elements of this study were:

• Subjects: All 32,844 individuals with a chronic kidney disease diagnosis in the Taiwan National Health Insurance Research Database. From this set 11,843 subjects had sufficient data for the study.
• Case definition: Influenza vaccination during the study period
• Outcome definition: Research database definition of dementia during follow up period
• Results: After controlling for confounding variables, influenza vaccination case subjects had a 36% lower rate of dementia diagnosis compared to those not vaccinated (odds ratio=.64)

Interestingly, there appeared to be a dose dependent effect with those receiving multiple influenza vaccinations showing even lower rates of dementia.

Also, somewhat unexpectedly, vaccinations given outside of the typical influenza season showed a greater effect.

The authors note in their discussion:

"In clinical practice, we suggest that CKD patients with high dementia risk be vaccinated."

The authors note dementia risk is increased in CKD with hypertension, high blood cholesterol and diabetes.

The most important potential implication in these two studies, is whether influenza might reduce dementia risk in the general non-medically ill population. I think we will have more research on this issue soon.

There are many reasons for regular influenza vaccination. Preserving brain health may be another important reason for expanded vaccination efforts.

You can access the free full-text manuscript of the CKD and dementia paper by clicking on the PMID link in the citation below.

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Figure of influenza virus in post is from Wikipedia Creative Commons file authored by: National Institutes of Health; originally uploaded to en.wikipedia by TimVickers (25 October 2006), transferred to Commons by Quadell using CommonsHelper

Liu JC, Hsu YP, Kao PF, Hao WR, Liu SH, Lin CF, Sung LC, & Wu SY (2016). Influenza Vaccination Reduces Dementia Risk in Chronic Kidney Disease Patients: A Population-Based Cohort Study. Medicine, 95 (9) PMID: 26945371

U.S. Flu Season 2015-16: Mild and Delayed

Credit U.S. Center for Disease Control

By at least one measure the 2015-16 influenza season in the U.S. was relatively mild and also delayed in it's peak.

The attached chart is from the CDC outpatient surveillance for influenza like illness. The rate for influenza symptom has be at the baseline level for the last three reporting cycles suggesting the end of the season for this cycle.

Peak rates for this cycle were the lowest in the last six years of data collection.

Congratulations to all who championed influenza vaccination in the United States this year!

An extended surveillance report from the CDC can be access HERE

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A Late Season Surge in U.S. Influenza

The CDC data surveillance on influenza is picking up an interesting pattern for 2015-2016 (See CDC chart).

The percentage of outpatient visits with influenza symptoms typically peaks around January 1, but this year (red triangle line) the number is continuing to increase making it the latest peak pattern.

Additional information about this year's influenza data from the CDC can be found here.

2015-16 CDC U.S. Influenza Trends: Bad Year or Not?

The U.S. Centers for Disease Control provides valuable data on tracking trends for influenza in the U.S.

The most recent trend using outpatient visit percentages is reproduced here. 

The trend for 2015-16 is below 2% of all outpatient visits through the most recent data.

However, the trends graph shows the typical epidemic period is still approaching. It will be a few more weeks before the 2015-2016 influenza trajectory can be assessed.

I have previously posted two items on the relevance of influenza to neuroscience medicine:

Prenatal influenza as a risk for pre-term birth (pre-term birth contributes to a variety of childhood brain disorders)

Prenatal influenza as a risk for adolescent and adult psychotic disorders

For more information on influenza trends in the U.S. from the CDC go here.

Figure is from CDC. Original is here.

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