Long-Term Antibiotic Use in Midlife Tied to Later Decline in Cognitive Function in Women

By Linda Carroll

March 24, 2022

NEW YORK (Reuters Health) - Women who report significant antibiotic use in midlife may be more likely to experience cognitive decline in later life, a new study finds.

An analysis of data from nearly 15,000 nurses revealed that women who reported at least two months of antibiotic exposure in midlife had lower mean cognitive scores seven years later, after adjustment for risk factors for cognitive decline.

The researchers behind the study, published in PLoS ONE, suggest the effect might be explained by changes in the microbiome due to the antibiotic use.

"A growing body of evidence supports that the gut microbiome may be linked to cognitive decline or the development of dementia," said Dr. Andrew T. Chan of Harvard Medical School and Massachusetts General Hospital, in Boston. "There is also evidence that long-term antibiotic use may alter the gut microbiome. Thus, our results showing that chronic antibiotic use in midlife was associated with cognitive function in later life supports a role for the gut microbiome on cognition."

To take a closer look at the impact of antibiotic use on cognition in older women, the researchers turned to the Nurses' Health Study II (NHSII), an ongoing U.S. nationwide prospective cohort study, which began in 1989 with an enrollment of more than 116,000 female nurses aged 25 to 42 years. NHSII asked participants to provide detailed information on lifestyle, medications and health-related factors via questionnaire every two years.

In 2009, NHSII researchers asked participants, whose mean age was 55 at the time, to report their total duration of antibiotic use in one of seven categories (ranging from none to three-plus years). An average of seven years later, the participants took a standardized and validated, self-administered online cognitive test battery (CogState).

Data on 14,542 of these women showed that increasing exposure to antibiotics at midlife was significantly associated with poorer scores on the CogState.

When the researchers compared women who used antibiotics to non-users, they found that women who used antibiotics for at least two months had mean scores that were lower by 0.11 standard units for global cognition, by 0.13 for psychomotor speed and attention and by 0.10 for learning and working memory, after adjustment for age and educational attainment of the parent and spouse (these data were used as a proxy indicator for socioeconomic status since the women were all nurses and therefore similar in education level).

The association remained even after adjustment for multiple risk factors for cognitive decline.

How could alterations in the gut microbiome impact cognition later in life?

"The gut microbiome may be associated with a chronic state of inflammation that may predispose to cognitive decline or poor brain health," Dr. Chan told Reuters Health by email. "The gut microbiome may also be associated with the production of specific proteins or metabolites that may influence cognition."

The research could lead to ways to protect the brain, Dr. Chan said.

"Our study supports a potential role of the gut microbiome on cognition, which opens new avenues of research into possible ways of modifying the gut microbiome to prevent cognitive decline with aging," he said. "This also underscores the importance of judicious use of antibiotics across the life course to minimize potential long-term consequences of altering the gut microbiome."

SOURCE: https://bit.ly/3qrHEv4 PLoS ONE, online March 23, 2022.