Tuberculosis Has Been Shown to Cause Dementia

Tuberculosis has a long history with dementia and specifically Alzheimer’s disease, one type of dementia.

Tuberculosis (TB) is caused by a slow growing bacterium with the name of Mycobacterium tuberculosis. The “myco” in mycobacterium refers to a thicker than normal cell wall. Because it grows slowly, TB spreads from person to person only through frequent and close contact. By breathing the bacterium, TB usually starts by attacking the lungs first and then spreads (seeding) to other parts of the body, including your kidneys, brain and spine. Wherever it seeds it damages the organ. In the kidneys it causes urine and blood in the urine (sterile pyuria), Pott disease (spondylitis) in the spine, hepatitis in the liver, lack of steroid hormones (Addison’s disease) in the adrenal gland, swelling in the neck (scrofula) in the cervical lymph nodes, and inflammation (meningitis) in the brain. Meningitis is the inflammation of the three membranes (meninges) protecting your brain and spinal cord. The tough outer membrane is called the dura mater, then the arachnoid and finally the delicate pia mater, the inner most layer that touches the brain. TB meningitis affects one in fifty cases of TB (much higher among children and those with HIV.) When these protective layers are attacked there are serious consequences to the brain.

The average survival with such TB–ridden brain was seven years, similar to the mortality span of Alzheimer’s disease. Most patients with Alzheimer’s disease typically die from infection or pneumonia and not cognitive decline—we will revisit this again later.

In 2010 Neil Anderson with Auckland City Hospital, New Zealand and his colleagues reported that people with TB meningitis had serious complications. Around a third suffered from a stroke, problems with eye/eyelid, pupil and lens, and epileptic seizures.  Around one in twenty suffered from the treatment itself (iatrogenic) through drug-induced hepatitis, while a fifth of the patients died early from the disease. For those that survive, one in ten had long-term cognitive impairment and/or epilepsy. With such dramatic complications it is surprising to realize how common TB remains to this day.

After HIV, TB is the major cause of death from a single infectious agent and is one of the top 10 causes of death worldwide with 1.8 million people dying from the disease in 2016. Drug-resistant strains of TB have already been identified in 105 countries including the U.S., and once infected, we cannot do anything but watch helplessly as the person dies.

But there is another twist to the story of this bacterium.

In 2017 Lawrence Broxmeyer with the New York Institute of Medical Research, undertook a historical review of how TB might have been the cause of Alzheimer’s disease even during Alois Alzheimer’s time. Broxmeyer argues that Alzheimer must have known this but elected to ignore it. By 2013 Francis Mawanda and Robert Wallace with the University of Iowa, reported that one of the prime suspects for Alzheimer’s disease was chronic bacterial infections like tuberculosis. The brilliant Oskar Fischer of the Prague clinic, a contemporary of Alois Alzheimer, noted this as well. The competition between Alzheimer’s Munich clinic (headed by Emil Kraepelin) and Fischer’s Prague clinic (headed by Arnold Pick) predestined animosity. And there was no collaborative effort to reconcile these observations about TB and Alzheimer’s disease. Instead the Munich clinic was out for glory and the creation of a “new” disease to enhance their legacy.

We continue discovering that there are many causes of Alzheimer’s disease. The disease is a reaction to these many traumas. In response to this trauma, studies are now strongly pointing to inflammation—a reaction to these traumas—that causes the damage to brain cells. Inflammation, seen as a penumbra on imaging techniques, is a shadow of dying cells in the brain. The question still remains how the inflammation—the penumbra—can be reduced and eliminated while for others the inflammation continues to grow nonstop. Each cause of dementia—for example, physical trauma from playing football or TB—will have its own pattern of progression. And this is the rub.

While federal funds are squandered on looking at the progression of the disease, the causes of dementia remain in the shadow of the research spotlight. The outcome of this ignorance is the utter lack of progress made in the last 100 years and the zero clinical outcomes from forty years of U.S. National Institute on Aging funding. Zero.

An alternate approach would be to focus on preventive measures. Not as sexy as “finding the cure” but we can guarantee success on day one. Diet and exercise, always a good strategy for a fulfilling life, is not enough. The low hanging fruit would involve protecting the head during contact sports and other activities where physical trauma eventually leads to dementia. Better vascular management, treatment and control are a second line of attack that will significantly reduce dementia rates. The third line of attack is to understand and control inflammation. It seems contradictory, but overall, in order to prevent dementia, research needs to move away from dementia and move again to basic science. Dementia is broader than what our focus has been so far. Historically politics dictated this narrow approach, but science is pointing in a different direction, but we seem to remain shackled to the past.

Emerging research shows that one type of trauma that causes dementia are bacteria, with TB being a very common bacteria agent among humans. But this is not just about “killing the bacteria.” Bacteria, and especially TB that we see today are not the same bacteria we saw a hundred or a thousand years ago. They have evolved with us. And they are still evolving and matching our development. We are evolving with them both as a species, as a community (different TBs across the globe) and as we age. This could (partially) explain why some people can control the spread of the penumbra, the inflammation, while others relent to its power.

Laura Pérez-Lago, from Madrid General Hospital and her colleagues found that there are many different types of tuberculosis bacterium within the same patient. They also found that individuals infected with TB might have genetics that promote TB to mutate. It seems that we continue co-evolving with the TB bacterium and some people allow for the bacterium to change within us while others restrict it from changing. Peng Yi-Hao, along with the China Medical University Hospital in Taiwan, looked at more than six thousand patients newly diagnosed with TB patients. Although patients that had TB were more likely to have other existing health problems—including; irregular heartbeat (atrial fibrillation), hypertension, diabetes, heart failure, stroke, depression, and head injury, all of which are correlated with increased risk for dementia—after controlling for these factors the overall risk of developing dementia in six years was higher, by an additional one person for every five in the non-TB patients. Among the patients with TB, men and people between 50 and 64 years were more likely to develop dementia compared to the TB-free group. Except for the patients with TB, those with a head injury exhibited the highest risk of developing dementia.

What seems to be emerging is that there is likely a genetic predisposition to allow TB to mutate and cause damage to many organs in the body, including the brain. Also with age we become more susceptible to TB and our inflammation response becomes a greater problem for the brain to cope with.

Nicholas Dunn with the University of Southampton, UK and his colleagues confirmed this point when they showed that elderly patients with dementia have a higher ratio of infection episodes in the four years preceding the diagnosis of dementia.  We become more prone to infections, which causes inflammation which harms us as we age.

The lesson that TB is teaching us is that we need to look at the many possible ways that the brain can be hurt. Focusing on the trauma that starts the cascade of inflammation is a sure bet to eventually be able to first understand the dementia and then perhaps cure it. Like cancer, dementia is neither simple nor static. The role of TB in causing dementia has waited too long to be given the importance it deserves.

© USA Copyrighted 2017 Mario D. Garrett  

References

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Pérez-Lago, L., Palacios, J. J., Herranz, M., Serrano, M. R., Bouza, E., & García-de-Viedma, Dario. (2015). Revealing hidden clonal complexity in Mycobacterium tuberculosis infection by qualitative and quantitative improvement of sampling. Clinical Microbiology and Infection, 21(2), 147-e1. 

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