“In a cohort of over 14,000 women, we observed that antibiotic use in midlife was significantly associated with subsequent poorer scores for global cognition, learning, and working memory, and psychomotor speed and attention,” write the researchers in their paper.

“To our knowledge, our study represents the first large study of chronic long-term use of antibiotics and subsequent cognition.”

The women in the cohort (a long-term chronic disease research project called Nurses’ Health Study) had taken antibiotic drugs for a variety of reasons, including for respiratory infections, dental problems, acne, and urinary tract infections.

For those on antibiotics, the resulting drop in brain power across the various categories of learning, response, and memory was the equivalent of about three or four years of normal aging, according to the data.