Antibiotic use in older adults not linked to cognitive impairment or dementia

Use of antibiotics by healthy elderly persons does not cause an increase in the risk of cognitive impairment or dementia, researchers reported on December 18, 2024 in Neurology.

“Antibiotics have been found in previous research to disrupt the gut microbiome, which is the community of tiny organisms that live in our intestines and support digestion,” said  author Andrew T. Chan, MD, MPH, Professor of Medicine at Harvard Medical School, Chief of the Clinical and Translational Epidemiology Unit, and the Program Director for gastroenterology training at Massachusetts General Hospital in Boston, Massachusetts. “Because the gut microbiome has been found to be important for maintaining overall health, and possibly cognitive function, there was concern that antibiotics may have a harmful long-term effect on the brain. Given that older adults are more frequently prescribed antibiotics and are also at higher risk for cognitive decline, these findings offer reassurance about using these medications.”

The investigators enrolled 13,571 healthy subjects over 70 (mean age 75 years, 54.3% female).

Subjects had no cognitive impairment and dementia during the first two years of the study.

The investigators used prescription records to ascertain use of antibiotics. They found that a total of 63% of the subjects were treated with an antibiotics at least once during that two-year period.

They divided the entire study group into two sub-groups, antibiotic users during the two-year period and antibiotic never-users during the same period.

The subjects were also divided into sub-groups according to the number of antibiotic prescriptions they had received in the two years, from 0 to over 5.

The investigators tracked the subjects for an average of 4.7 additional years. During this period, 461 subjects developed dementia and 2,576 people developed cognitive impairment.

At baseline, subjects took cognitive tests. They did so again after one year. The testing was repeated every two years thereafter. The testing showed changes in cognition and memory skills like attention, executive function and language.

Upon comparing the data from antibiotic users and non-users, the investigators concluded, “Compared with nonuse, antibiotic use was not associated with increased risks for dementia.”