What we know about the link between taking antibiotics and cognitive deterioration

Currently there is a post circulating on several Telegram channels that echoes a study in which several scientists supposedly had found “an as-yet unexplained link between antibiotics and cognitive deterioration”. However, it is a MISLEADING headline: yes, one recent study has shown that there could be a link between taking antibiotics and cognitive deterioration. However, the researchers only considered the consequences of the prolonged consumption (two months or more) of these medications.

An as-yet unexplained link between antibiotics and cognitive deterioration has been revealed.

The study has been shared on various media outlets, but the way in which some of them are written, such as the one circulating in certain Telegram groups, seems to indicate that even just taking an antibiotic occasionally can affect the brain. But that is not what the scientists discovered. What’s more, their results are not conclusive.

A survey of almost 15,000 nurses

The scientists arrived at their results, published in the journal Plos ONE, after performing a series of surveys on a cohort (Spanish only) of 14,542 nurses who had been part of the Nurses’ Health Study II carried out by Harvard University (USA). The scientists noticed that the nurses, with an average age of 54 years, who had taken antibiotics for at least two months in this period of four years (between 2014 and 2018) had lower mean cognitive scores in tasks related to working memory, learning, attention and psychomotor speed in comparison to those who had not taken antibiotics for that much time. “Our study does not show that antibiotics cause cognitive deterioration; rather, it raises the concern that antibiotics may lead to worse cognition”, Raaj Mehta explains to Verificat. Mehta is a doctor in the Clinical and Translational Epidemiology unit at Massachusetts General Hospital (USA) and head researcher of the study.

In other words, what the scientists found was that there was a cognitive deterioration in the seven years after taking antibiotics. But it does not mean that the cause of the deterioration is specifically the consumption of antibiotics, and it is certainly not the case in all populations, age groups or doses.

Limitations of the study

The study has several limitations that must be considered. One is that it did not make a comparison between healthy and unhealthy women, instead obtaining the data in retrospect directly from a group of patients who were prescribed antibiotics for a period of two months at a particular point in their life.

Another limitation is that the scientists did not take into account the specific type of antibiotic they analysed and instead based it on drugs prescribed to treat various types of illnesses.

Finally, the sample was not representative of the entire population, given that the data was “restricted to women” whose cognitive function “may differ with respect to men”, the study’s authors explain. In other words, they continue, “the rates of cognitive deterioration may be different between women and men as well as among different racial and ethnic groups”, hence the need for “more studies in a number of populations”.

The study will have the last word

As we have explained on other occasions (Spanish only), clinical trials undergo various phases until a concrete hypothesis is confirmed. It is not possible to extrapolate the results of a survey of roughly 15,000 nurses to the entire population, although it is true that the study does not discard that hypothesis either.

What could be the conclusive evidence that gives us a clear answer on the issue? Mehta explains to Verificat that “a clinical trial would be needed to prove that antibiotics cause cognitive deterioration”. In other words, it would require randomised trials with at least two groups to judge whether there is a cognitive deterioration after taking antibiotics in the experimental group versus the control group.