What’s the connection between flu vaccination and lower risk of Alzheimer’s Disease?

As far fetched that it may sound, there is growing evidence that flu vaccination is associated with lower risk of being diagnosed with Alzheimer’s Disease (AD).1

The most compelling evidence to date comes from a 2022 retrospective, propensity-matched study involving a nationwide sample of over 2 million U.S. adults ≥ 65 years old.1  This study found a 40% reduction in the risk of incident AD during the 4-year follow-up period when individuals receiving at least 1 dose of flu vaccine were compared to those who did not receive flu vaccination during the study period (number needed to treat-NTT 29.4). 

Despite its limitations, the results of the above study were concordant with those of several smaller studies that found an association between flu vaccination and lower risk of dementia of any cause.1-3  A 2022 meta-analysis also concluded that flu vaccination was associated with significantly lower risk (33%) of dementia among older people. Interestingly, in a study involving veterans, receipt of ≥6 doses of flu vaccines (not fewer) was associated with lower risk of dementia.4

Several hypotheses have been posited to explain the potential beneficial impact of flu vaccination on the risk of dementia, including: 1. Influenza-specific mechanisms, such as mitigation of damage secondary to influenza infection and/or epitopic similarity between influenza proteins and AD pathology; 2. Non-influenza-specific training of the innate immune system; and 3. Non-influenza-specific changes in adaptive immunity via lymphocyte-mediated cross-reactivity.1

So, in addition to its protective effect against severe influenza,5 and its association with lower risk of hospitalization for cardiac disease and stroke and reduction in death due to combined cardiovascular disease events (eg, heart attacks/strokes),  flu vaccination may be protective against AD! Who would have thought that a simple vaccine may have far reaching health benefits?

Bonus Pearl: Did you know that mice infected with non-neurotropic influenza strains have been found to have excessive microglial activation and subsequent alteration of neuronal morphology, particularly in the hippocampus, and that in APP/PS1 transgenic mice, peripheral influenza infection induces persistent elevations of amyloid- (A) plaque burden?Intriguing indeed!!!

Liked this post? Download the app on your smart phone and sign up below to catch future pearls right into your inbox, all for free!

Subscribe to Blog via Email

Enter your email address to subscribe to this blog and receive notifications of new posts by email.

References

  1. Bukhbinder AS, Ling Y, Hasan O, et al. Risk of Alzheimer’s disease following influenza vaccination: A claims-based cohort study using propensity score matching. Journal of Alzheimer’s Disease 2022; 88:1061-1074. https://pubmed.ncbi.nlm.nih.gov/26945371/  
  2. Liu JC, Hsu YP, Kao PF, et al. Influenza vaccination reduces dementia risk in chronic kidney disease patients: A population-based cohort study. Medicine (Baltimore) 2016 95 :32868. https://pubmed.ncbi.nlm.nih.gov/26945371/
  3. Wiemken TL, Salas J, Hoft DF, et al. Dementia risk following influenza vaccination in a large veteran cohort. Vaccine 2021;39:5524-5531. https://pubmed.ncbi.nlm.nih.gov/34420785/
  4. Veronese N, Demurtas J, Smith L, et al. Influenza vaccination reduces dementia risk: A systematic review and meta-analysis. Ageing Res Rev 2022;73:101534. https://pubmed.ncbi.nlm.nih.gov/34861456/
  5. Godoy P, Romero A, Soldevila N, et al. Influenza vaccine effectiveness in reducing severe outcomes over six influenza seasons, a case-cae analysis, Spain, 2010/11 to 2015/16.  Euro Surveill 2018;23:1700732. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6208006/
  6. Hosseini S, Michaelsen-Preusse K, Schughart K, et al. Long-term consequences of non-neurotropic H3N2 influenza A virus infection for the progression of Alzheimer’s Disease symptoms. Front. Cell. Neurosci 28 April 2021; https://doi.org/10.3389/fncel.2021.643650 https://www.frontiersin.org/articles/10.3389/fncel.2021.643650/full

Disclosures: The listed questions and answers are solely the responsibility of the author and do not necessarily represent the official views of Mercy Hospital-St. Louis, Massachusetts General Hospital, Harvard Catalyst, Harvard University, their affiliate academic healthcare centers, or its contributors. Although every effort has been made to provide accurate information, the author is far from being perfect. The reader is urged to verify the content of the material with other sources as deemed appropriate and exercise clinical judgment in the interpretation and application of the information provided herein. No responsibility for an adverse outcome or guarantees for a favorable clinical result is assumed by the author. Thank you!

 

What’s the connection between flu vaccination and lower risk of Alzheimer’s Disease?

Can Covid-19 exacerbate seizures in patients with epilepsy?

There have been several reports of seizure exacerbation in epileptic patients after Covid-19 infection. Seizure exacerbations have been observed in epileptic patients with uncontrolled epilepsy, as well as patients who were previously controlled with antiepileptic drugs (AEDs).1,2

In a survey of 362 epileptic patients in Wuhan, China, the site of the initial outbreak, 31 (8.6%) patients reported an increased number of seizures in the month after the public lockdown began; 16 (51.6%) of the 31 patients with seizure exacerbation had prior exposure to Covid-19.1

In a study of 439 patients with Covid-19 infection in Egypt, 19 (4.3%) patients presented with acute seizures.2  Two of the 19 seizure patients had a previous diagnosis of epilepsy, which had been controlled for up to 2 years. Interestingly, the other 17 patients had new onset seizures without a previous epilepsy diagnosis.

Covid-19 has been proposed to induce seizures by eliciting inflammatory cytokines in the central nervous system, leading to neuronal necrosis and increased glutamate levels in the cerebral cortex and hippocampus.3

Covid-19 infection may have also indirectly caused seizure exacerbations in a number of epileptic patients. Interestingly, stress related to worrying about the effect of the outbreak on a patient’s seizure activity was associated with seizure exacerbations (odds ratio: 2.5, 95% CI: 1.1-6.1)2. It is also possible that some seizure exacerbations may have been due to fear of visiting the hospital and AED withdrawal, as was demonstrated during the 2003 SARS outbreak.4

Bonus Pearl: Did you know that Guillain–Barré Syndrome has also been observed in patients with Covid-19 infection?5

Contributed by Luke Vest, Medical Student, St. Louis University Medical School

Liked this post? Download the app on your smart phone and sign up below to catch future pearls right into your inbox, all for free!

Subscribe to Blog via Email

Enter your email address to subscribe to this blog and receive notifications of new posts by email.

References:

  1. Huang, S., Wu, C., Jia, Y., et al. (2020). COVID-19 outbreak: The impact of stress on seizures in patients with epilepsy. Epilepsia, 61(9), 1884-1893. https://doi.org/10.1111/epi.16635  
  2. Khedr, E. M., Shoyb, A., Mohammaden, M., & Saber, M. (2021). Acute symptomatic seizures and COVID-19: Hospital-based study. Epilepsy Res, 174, 106650. https://doi.org/10.1016/j.eplepsyres.2021.106650
  1. Nikbakht, F., Mohammadkhanizadeh, A., & Mohammadi, E. (2020). How does the COVID-19 cause seizure and epilepsy in patients? The potential mechanisms. Multiple sclerosis and related disorders, 46, 102535. https://doi.org/10.1016/j.msard.2020.102535
  2. Lai, S. L., Hsu, M. T., & Chen, S. S. (2005). The impact of SARS on epilepsy: the experience of drug withdrawal in epileptic patients. Seizure, 14(8), 557–561. https://doi.org/10.1016/j.seizure.2005.08.010
  3.  Abu-Rumeileh, S., Abdelhak, A., Foschi, M., Tumani, H., & Otto, M. (2021). Guillain-Barré syndrome spectrum associated with COVID-19: an up-to-date systematic review of 73 cases. Journal of neurology, 268(4), 1133–1170. https://doi.org/10.1007/s00415-020-10124-x   

Disclosures: The listed questions and answers are solely the responsibility of the author and do not necessarily represent the official views of Mercy Hospital-St. Louis or its affiliate healthcare centers, Mass General Hospital, Harvard Medical School or its affiliated institutions, or St. Louis University Medical School. Although every effort has been made to provide accurate information, the author is far from being perfect. The reader is urged to verify the content of the material with other sources as deemed appropriate and exercise clinical judgment in the interpretation and application of the information provided herein. No responsibility for an adverse outcome or guarantees for a favorable clinical result is assumed by the author. Thank you!

Can Covid-19 exacerbate seizures in patients with epilepsy?

Can a seizure cause abnormalities on the brain MRI?

Yes it can, and the MRI abnormalities could represent seizure’s effects on the brain, not the seizure’s structural cause. Seizure-related MRI changes are often associated with status epilepticus, but have also been reported in complex partial status epilepticus.1,2

T2-weighted MRI images may show increased signal intensity at the cortical gray matter, subcortical white matter, or hippocampus. The MRI changes are unilateral about one-half of the cases, while in about 8% of patients leptomeningeal contrast-enhancement may be observed. Partial simple and complex seizures are associated with hippocampal involvement.3

The increased signal intensity following seizures is thought to be due to increased metabolism at the epileptogenic area, which in turn results in increased oxygen consumption, hypoxia, hypercarbia, lactic acidosis, and ultimately vasodilation and edema.

Reversibility of MRI changes following seizures has been noted between 15 and 150 days (average, 62 days). A structural abnormality is more likely the cause of a seizure when the MRI changes do not resolve during this period.3 Therefore, seizure-induced brain-MRI abnormalities remain a diagnosis of exclusion.

References

  1. Kim JA, Chung JI, Yoon PH, et al. Transient MR signal changes in patients with generalized tonicoclonic seizure or status epilepticus: periictal diffusion-weighted imaging. Am J Neuroradiol 2001; 22:1149–1160 http://www.ajnr.org/content/22/6/1149.long
  2. Henry TR, Brunberg DI, Pennell PB, et al. Focal cerebral magnetic resonance changes associated with partial status epilepticus. Epilepsia 1994; 35:35–41 http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.916.5237&rep=rep1&type=pdf
  3. Cianfoni A, Caulo M, Cerase A, et al. Seizure-induced brain lesions: a wide spectrum of variably reversible MRI abnormalities. Eur J Radiol. 2013; 82(11):1964-72. http://www.ejradiology.com/article/S0720-048X(13)00271-4/fulltext

 

Contributed by Johan H.L. Boneschansker, MD, Mass General Hospital, Boston, MA.

Can a seizure cause abnormalities on the brain MRI?