Birth cohort or measurement protocol differences?
Studies have reported age-related differences in blood pressure (BP) utilizing cross-sectional designs  as well as trajectories of BP in longitudinal designs . However, little research examines whether and in what way the age-related trajectories of BP change over time. In this issue of Journal of Hypertension, Joas et al. compared the trajectories of BP over 10 years in 70–80-year-olds from two Swedish birth cohorts approximately 30 years apart.