Using Antibiotics May Increase Risk of Developing ALS, Swedish Study Suggests

Using Antibiotics May Increase Risk of Developing ALS, Swedish Study Suggests

Using antibiotics may increase the risk of developing amyotrophic lateral sclerosis (ALS), with a higher number of prescriptions linked to greater risk, a nationwide study in Sweden suggests. 

However, the researchers caution that more studies are needed to prove a direct, cause-and-effect relationship between antibiotics use and ALS.

For the study, titled “Antibiotics Use and Risk of Amyotrophic Lateral Sclerosis in Sweden,” researchers investigated the association between antibiotics and the future risk of ALS by comparing the medicine’s use by 2,484 ALS patients, and the general population in Sweden. The report was published in the journal European Journal of Neurology.

Studies in animal models previously suggested that changes in gut bacteria, or gut microbiota, might be associated with ALS. However, results addressing this possibility in humans have been conflicting.

Antibiotics are well known to greatly change the composition of intestinal bacteria. Broad-spectrum antibiotics, for instance, were shown to alter 30% of gut bacteria, reducing their diversity.

Given the impact of these medicines in gut microbiota, the researchers investigated whether individuals who use antibiotics are at a higher risk of developing ALS. The team addressed this question retrospectively, examining data from all prescriptions given since July 1, 2005 in Sweden, using several national health registers.

The researchers investigated how many antibiotics were given to a total 2,484 ALS patients before they were diagnosed with the disease, between 2006 and 2013. This data was compared with prescriptions given 12,420 healthy people, matched by sex, age, and area of residence.

Antibiotics included those used for respiratory infections — amoxicillin, penicillin, cephalosporin, and macrolides — and those prescribed to treat urinary tract and skin and soft tissue infections, including pivmecillinam, sulphonamide, trimethoprim, norfloxacin, ciprofloxacin, nitrofurantoin, flucloxacillin, cloxacillin, and dicloxacillin.

To account for delays in ALS diagnosis, all prescriptions within one year before diagnosis were excluded from the main analysis.

The data showed that people who were prescribed antibiotics, even once, had a slightly higher risk of developing ALS later on.

Moreover, that risk increased with the number of antibiotic prescriptions. The risk was higher for people who had been prescribed the medicine two to three times before, and even greater if they had been given it four times or more.

Similar results were noted regardless of whether the antibiotics were used for respiratory infections, or urinary or skin and soft tissue infections.

However, after specifically examining each type of antibiotics, the investigators found that the risk of ALS was especially increased for those who had received more than two prescriptions of beta-lactamase sensitive penicillins. These penicillins are used to treat more resistant types of some infections.

The researchers found that ALS patients had used antibiotics more often (65.1%) than the general population (61.8%). The increased use among people with ALS was seen as early as six to eight years before diagnosis, and increased sharply over the year immediately prior to diagnosis.

“In conclusion, we found that antibiotics use, especially repeated use, was associated with an increased risk of ALS,” the researchers said.

“The precise biological mechanisms underlying such a relationship remain to be clarified. However, a biological pathway through the altered gut microbiome might be at play,” they added.

Although this was a large, nationwide study, the investigators cautioned that the results are only suggestive, and said more evidence is needed before any cause-and-effect relationship can be claimed.

The study did not account for other potential risk or protective factors for ALS, such smoking, alcohol use and diet.

“[I]t is difficult to disentangle the effect of antibiotics from the effect of the underlying indications for the use of antibiotics, i.e. infections that might be secondary to the underlying ALS disease,” the researchers said.
That means the findings “are only suggestive and cannot prove causality,” they added.
Another important factor, the researchers said, is that the study is based on antibiotics prescribed and dispensed, which does not mean that all people were effectively taking them.


  1. Bill says:

    Unfortunately many people will read this and have one take. Antibiotics cause ALS. The data certainly is not very striking, is potentially inflammatory to those people fearing medication and in my opinion way too early to publish.

  2. Semir says:

    Sounds very inconclusive. Does not look like a statistically significant difference – 61% vs 65%.

    And even if it were true, what if the underlying reason for the ALS is some stubborn infection or inflammation contracted in the years before the diagnosis, and the frequent need for antibiotics was actually an early indicator of ALS-to-come?

  3. I have been working on the theory that my own personal case of ALS is due to a disturbed gut microbiome. In the summer of 2007, I got a nasty gut infection and i took a series of different antibiotics in order to try to destroy the infection. I was also swimming in a polluted lake every day during the time I took those antibiotics. It is a very reasonable theory that I swallowed enough water to reseed my gut microbiome in a very unhealthy way.

    I tried fecal transplantation a total of 7 times between late 2015 and early 2017 with no notable results.I did not take any antibiotics in association with those first seven trials.
    More recently I had a urinary tract infection, and I supplemented those antibiotics by two other types in an attempt to kill as much as possible of my microbiome. Then I did a fecal transplant twice, one day and two days after stopping the antibiotic treatment. That was in February and since then I have been improving.

    I do realize there is no way to untangle the possible placebo effect from my actual symptoms however I will be going in for my breathing test in a few days and if my breathing improves substantially I will certainly volunteer for the study of patients who improved by my doctor, doctor Brooks and also doctor bedlack of Duke University.

    I have had a long email conversation with James Metcalf in particular who is microbiologist on the team looking into the bmaa/ALS connection. I believe in fact that my case of ALS may be mediated by bmaa that is being produced in my gut buy a strain of Malainabacteria that has taken up residence in my colon.

    This is all based on current research findings and not something crazy. I bemoan the fact that I have been unable to have the BMAA-level analyzed in my stool. I pray that my improvement datapoint will motivate some researchers to develop methods to measure both bmaa and to find the bacterial genes that synthesize bmaa in my stool.

    • Anna says:

      Thats very interesting. Can you keep us updated on the results of the breathing test?
      I was harmed by Cipro and levaquin in 2014 and 16 and Tool flagyl and amoxicillin last summer. Since then neuropathy and speech issues. Balance issues and now weekness of tounge, mouth And throat muscles and right arm and hands along with fasciculations all over my body. No diagnosis yet but appointment next week for testing since doctor suspects ALS.
      I was thinking about fecal transplant aswell.

  4. Theo van Eerden says:

    I got a prescription for antibiotics for the last 30 yrs for every visit to the dentist because I suffered from endocarditis a long time ago. Maybe the cause of my ALS?

  5. Alfred Miller,M.D. says:

    ALS is caused by Borrelia Burgdorferi.
    Proper testing (not CDC) will confirm the diagnosis and treatment with appropriate antibiotics will eradicate this infection.
    Alfred Miller,M.D.

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