Blood biomarkers offer a less invasive and cheaper method for identifying Alzheimer's disease (AD)-related changes. Already, blood biomarkers for AD are being adopted by clinical practice and their use will only expand in coming years. However, blood biomarkers are susceptible to fluctuations not yet well characterized. Such fluctuations, although rarely observed in current research settings, may influence the biological evaluation of dementia once implemented into routine settings. The study at present aims to identify how blood biomarkers fluctuate over a short period of time in the same individual and assess drivers of these fluctuations.