Early detection is crucial for diseases such as dementia and cancer. In aiming to treat these diseases, it is effective to detect the pre-disease state, a stage even earlier than the early stage of the disease, where symptoms have not yet manifested. It has already been proven that specific glycan changes can serve as biomarkers for various diseases (especially cancer), and it has also been found that there are glycans that change with the onset of diseases such as dementia and cancer. In the future, it will be required to use specific glycan changes as pre-disease diagnostic markers. Currently, there are still few candidates for glycan biomarkers to explore such pre-disease states, but it has been reported that there are glycan changes in IgG before the onset of rheumatoid arthritis [1]. The development of these pre-disease markers is an important issue for future glycoscience. Currently, the Human Glycome Atlas (HGA) Project, which analyzes the relationship between glycan changes and dementia and aging on a large scale, is underway, and the development of pre-disease markers is expected.