A study that appeared recently in the open-access journal PLOS ONE shows that the use of antibiotics in midlife by women could promote cognitive decline years later.
The large-scale study was carried out by scientists from Massachusetts General Hospital, Harvard Medical School, and Harvard T.H. Chan School of Public Health. Researchers from Rush Medical College and Boston’s Brigham and Women’s Hospital also took part.
Subjects who used antibiotics for months during a period returned lower scores in neuropsychological tests done several years later. The effects were comparable to those of up to four years of aging.
Antibiotics and cognitive function
On what could be responsible for the observed outcomes, Harvard Medical School gastroenterologist Andrew Chan stated that a disruption of the gut microbiota is the most likely explanation, according to Medscape Medical News. It is also possible that the drugs work directly on the brain to cause cognitive decline, however.
Studies have revealed a link between gut microbiota and brain health via what is known as the gut-brain axis. This means that the gut communicates with the central nervous system. It is not surprising then that what affects the gut may impact mental health.
In one study, people with Alzheimer’s were found to have a modified gut microbiome when compared to healthy individuals. They had more of the clinical pathogens Bacteroides while having less of the beneficial Bifidobacterium species, as an example.
Previous research also shows that the use of antibiotics can cause major microbiome disruptions, leading to undesirable effects. Chan said the drugs and the resulting disruptions could set off “a chronic state of inflammation that predisposes people to cognitive decline.”
In mice, for example, scientists have shown a link between antibiotic use and gut dysbiosis as well as cognitive impairment. But these drugs were not detected in the brain.
One of the ways gut microorganisms impact mental health is by promoting the release of neurotransmitters. They can help to activate the vagus nerve and are able to relate with immune cells.
Cognitive impairment in women
For this research, scientists made use of data from the Nurses’ Health Study II. This is an ongoing effort that collects female nurses’ health data over several years.
The research team examined the information of more than 15,000 female nurses as regards antibiotic use and their performance in cognitive tests. It divided the nurses into groups based on their antibiotic use, ranging from no use to using for more than two months.
The researchers, who honed in on middle-aged female nurses with a mean age of 54.7 years, compared people who used antibiotics over different lengths of time to people who did not use them. These subjects were assessed on cognitive tests relating to memory, attention, learning, and thinking speed. The tests were conducted seven years after antibiotic use.
Female nurses who used antibiotic drugs for at least two months returned lower cognitive scores, compared to those who used them for shorter durations or took none.
The scientists compared the extent of observed cognitive decline to between three and four years of aging.
However, Chan noted that it was too early to use these findings for recommendations on antibiotic use with a view to protecting mental health. It only shows a need for caution when using these drugs for now.