Background American and European guidelines define hypertension differently and are sex agnostic. Our aim was to assess the impact of different hypertension thresholds at the age of 40 on 30-year stroke risk and to examine sex differences.Methods We included 2608 stroke-free individuals from the Akershus Cardiac Examination 1950 Study, a Norwegian regional study conducted in 2012–2015 of the 1950 birth cohort, who had previously participated in the Age 40 Program, a nationwide health examination study conducted in 1990–1993. We categorised participants by systolic blood pressure (SBP) at age 40 (