Are Antibiotics Causing Cognitive Decline?
By Maggie Walsh ‘25
Commonly referred to as the ‘second brain,’ the gut microbiome has repeatedly been shown to have close ties with cognitive functioning and mental health. The gut microbiome is composed of over 100 trillion microbes, both good and bad, which inhabit your digestive system. Each microbiome has a unique composition, with great disparities in the balance between harmful and helpful bacteria. The potential implications of a healthy microbiome have only recently been realized, and, even with relatively little research, we are already uncovering the strong effects that the gut microbiome composition has on physical health, immune function, mental well-being, and cognitive processes. While the composition is partly a product of genetics and early life experiences, there are many concrete steps which can be taken to promote a more favorable balance of bacteria in the gut. Likewise, there are many behaviors which seem to damage the microbiome, and, unfortunately, some of these behaviors, such as antibiotic use, are an inevitable part of daily life.
Antibiotics work by impeding vital processes of bacteria, which either kills them or takes away their ability to multiply. When there is unwanted bacteria in our body, this function of antibiotics is extremely beneficial; in fact, antibiotics have saved millions of lives. While some antibiotics are highly specialized and only attack certain types of bacteria, many attack a broad range of bacteria. This broad range often includes good bacteria, and killing those can upset a healthy microbiome.
While few studies have examined the relationship between chronic antibiotic use and cognitive decline in midlife patients without dementia, a recent study done between Massachusetts General Hospital and Harvard Medical School analyzed this relationship for 15,000 women with an average age of 54.7 years and no universal health issues. The study looked at a health questionnaire which gave insight into the women’s degree of antibiotic use over the last four years. The categories used to communicate antibiotic use were no use, less than 15 days, 15 days to 2 months, and over 2 months. Then, roughly seven years after their listed antibiotic exposure, these women were cognitively tested using a card stimulation assessment. Psychomotor speed was tested through one’s ability to quickly identify and detect cards, and working memory was tested through one’s ability to recall information pertaining to the cards. After adjusting for age-related differences and relevant risk factors, researchers found that just two months of antibiotic exposure was associated with decreases in psychomotor speed and working memory. While these differences are relatively small, they correspond with the magnitude of cognitive decline which typically occurs with about 3-4 years of aging. This cognitive decline is thought to stem from the killing of good bacteria and the subsequent upset of the gut microbiome balance.
This study adds to the plethora of studies which exemplify the various ways in which antibiotic use may have harmful long-term effects and provides insight for these harmful effects on a prominent yet understudied group of people: middle aged women of average health. While this relationship cannot be confirmed until further studies are conducted, there is ample evidence at this time to warrant caution when proceeding with antibiotics. This is not to say you should completely forgo antibiotic use; many times, antibiotics have net positive effects and are necessary. It is to say, however, that antibiotics should not be taken in a careless manner or without need. Before deciding to consume antibiotics, one should consult with a healthcare professional and take into account the effects that this decision will have on their microbiome composition.
It seems that each additional study in this quickly growing field of gut microbiome research makes us increasingly appreciate how influential the gut microbiome, and thus behaviors which alter its composition, are to our health and well-being. The need for further research cannot be understated. At this time, we are unsure of the reversibility of the negative cognitive effects associated with chronic antibiotic use. Could it be possible to regain cognitive function if the microbiome is altered back to a more favorable composition? If so, what would be the expected timeline of such an occurrence? If the current trend in the field of gut microbiome research continues, we should have answers to questions like these and many more in the near future.
At this time, we understand that antibiotic use is not the sole determinant of gut microbiome health. Thankfully, there are plenty of steps which can be taken by all, regardless of their status of antibiotic use, to promote a healthy gut microbiome. For now, do your microbiome a favor; be sure to eat a diverse diet with lots of plants, get adequate sleep, limit stress, move your body, and avoid unnecessary antibiotic use.
Sources:
Can Chronic Antibiotic Use Cause Cognitive Decline?
10 Ways to Strengthen Your Microbiome
Antibiotic Use Midlife May Lead to Cognitive Decline in Women
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