Research published in The Lancet suggests that a blood test may be capable of identifying signs of Alzheimer's disease decades before clinical symptoms manifest. The study focused on biomarkers such as tau proteins and amyloid-beta (Aβ), which are linked to cognitive decline. Conducted with 1,350 dementia-free adults averaging 61 years old, the research found that 6% exhibited elevated levels of these biomarkers, correlating with poorer cognitive performance and faster decline in memory and processing speed over five years. The findings highlight the potential for early detection, which could enable interventions targeting modifiable risk factors like physical inactivity and poor sleep. However, experts from Karolinska Institutet caution that blood tests may yield false positives in younger, cognitively unimpaired individuals, emphasizing the need for additional diagnostic criteria. This study is part of a special issue of The Lancet focused on neurology, indicating a growing interest in early Alzheimer's detection methods.