Long-Term Antibiotic Use and Dementia Risk in Older Adults: What’s the Link?

Antibiotic use does not increase the risk for dementia; cognitive impairment, no dementia (CIND); or cognitive decline among healthy older adults. These are the findings of a study published in Neurology.

In previous studies, researchers have found that amyloid-like peptides can be produced by the microbiota in the gut. As antibiotics can alter the biodiversity of gut microbiota, they may affect the risk for dementia onset.

A team of researchers from Massachusetts General Hospital and Harvard Medical School sourced data for this study from the ASPirin in Reducing Events in the Elderly (ASPREE; ClinicalTrials.gov Identifier: NCT01038583) study, which was a randomized, placebo-controlled trial conducted in Australia between 2010 and 2014. Use of antibiotics in the first 2 years of ASPREE follow-up, according to the Pharmaceutical Benefits Scheme (PBS), was associated with risk for dementia onset.

The participants who did (n=8481; mean age, 74.9; women, 56.1%; White, 98.6%) and did not (n=5090; mean age, 75.0; women, 51.3%; White, 98.6%) use antibiotics had a body mass index (BMI) of 28±4.6 and 27.7±4.4 kg/m² (P <.0001), and 24.9% and 24.6% had a family history of dementia, respectively.

Among participants who used antibiotics, the most common antibiotics included beta-lactams (57.2%); other beta-lactams (49.3%); and macrolides, lincosamides, and streptogramins (26.7%).

During a median follow-up of 4.70 years, 461 incident dementia cases and 2576 CIND cases were observed.

In the minimally adjusted model, antibiotic use in the first 2 years of follow-up did not increase risk for incident dementia (adjusted hazard ratio [aHR], 1.06; 95% CI, 0.88-1.28; P =.541) but did increase risk for CIND (aHR, 1.09; 95% CI, 1.01-1.18; P =.031). However, in the fully adjusted model, antibiotic use was not associated with CIND risk (aHR, 1.02; 95% CI, 0.94-1.11; P =.686).

Stratified by antibiotic subclass, no significant trends in dementia or CIND risk were observed.

Similarly, in the subgroup analyses, no significant interactions were observed, however, antibiotic use tended to increase risk for CIND among individuals with a 10-item Center for Epidemiologic Studies Depression (CESD-10) score of 8 or greater (P =.05).

Antibiotic use was not associated with longitudinal changes in psychomotor speed (B, 0.01; P =.39), global function (B, -0.009; P =.60), language and executive function (B, -0.03; P =.15), episodic memory (B, -0.02; P =.28), or composite (B, -0.02; P =.13) cognitive test scores.

The major limitation of this study was the reliance on PBS data which only contains information about antibiotic prescription fills and not data on antibiotic use.

“[A]mong adults aged 70 years and above, antibiotic use was not associated with incident dementia, CIND, or greater declines in cognitive testing scores over time. Our findings provide reassurance that episodic antibiotic use in cognitively intact, community-dwelling older adults is unlikely to lead to future impairment in cognitive function,” the researchers concluded.

Disclosure: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.