Gut microbiota dysbiosis are likely to be involved in the development of dementia. Antibiotics is one of the main cause of dysbiosis. However, some dementia animal studies show that antibiotic is beneficial. And the associations between antibiotics and cognition decline or dementia remain unclear. Therefore, our objective is to investigate the associations between antibiotic use and cognition decline or dementia risk in the large, prospective UK Biobank study. To assess these associations, we will use statistical models which take into account variables that may affect cognition and dementia, such as education, income, hypertension, diabetes, and gene. These findings can provide evidence and further understand the role of antibiotics in dementia, and provide evidence for continued exploration of antibiotic use. Findings from this study may also have major implications for prescribing practices and public health.