FLAME is an online ageing cohort with extensive longitudinal cognitive and health data from over 50,000 participants in the UK, Norway, Canada and the US. The system can detect statistically meaningful age-related cognitive decline, with concurrent validity with established, FDA-approved criteria for early cognitive impairment (P<0.0001) and sensitivity to the trajectory of cognitive decline in healthy and impaired individuals. There is also good evidence for health and lifestyle factors that influence prognosis and risk.