A new study suggests that antibiotics do not impair cognitive function in older adults or increase their risk of dementia.
Researchers from Harvard University published these findings in the international journal Neurology.
This study contrasts with previous research from Seoul National University in 2022, which found that adults over 40 who were prescribed antibiotics for more than three months had a 44% higher risk of developing dementia compared to those who weren’t. That study also indicated a 46% increase in Alzheimer’s disease risk.
Andrew Chan, a gastroenterology professor at Harvard Medical School and the study’s lead author, observed that previous studies have demonstrated that antibiotics disrupt the gut microbiome. This microbiome is the community of tiny organisms living in the gut that aid digestion.
He explained that given the crucial role of gut microbiota in overall health and cognitive function, there were concerns about antibiotics’ potential long-term adverse effects on brain health, necessitating further investigation.
The team analyzed data from over 13,500 healthy Australians aged 70 and above who participated in a clinical trial examining the health benefits of low-dose aspirin.
Using prescription records, they found that about 63% of participants had used antibiotics at least once during the two-year study period.
The researchers monitored the participants’ brain health for an average of five years, regularly assessing memory, attention, executive function, language, and reasoning skills. During this time, nearly 2,600 participants developed cognitive impairment, and over 460 were diagnosed with dementia.
Surprisingly, the study found no significant cognitive differences between seniors who took antibiotics and those who didn’t. Even after accounting for other risk factors linked to cognitive decline, antibiotic use was not associated with cognitive impairment or dementia.
The researchers also found no link between cognitive issues and cumulative, prolonged, or specific types of antibiotic use.
Chan stated that the findings should reassure older adults, who often receive antibiotic prescriptions and face a higher risk of cognitive decline, that the use of antibiotics is likely safe in terms of brain health.
However, he acknowledged the study’s limitations, noting that the research involved relatively short-term follow-up of older adults. He emphasized that more extensive studies are needed to confirm whether antibiotics have any long-term effects on brain health.
Hongkai Ji and Alden Gross from Johns Hopkins Bloomberg School of Public Health also pointed out that the study’s other limitation is that prescription records might not accurately reflect actual antibiotic use.
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