Figure 1

Search flow chart for the simultaneous retrieval of retrospective cohort data and trial participant data. For the RCT we need patients with hypothyroidism and who were ≥80 years old in 2012. For the retrospective cohort study we need patients with a diagnosis of hypothyroidism who were ≥80 years old in 2008, and followed up (alive and dead) until 2012. RCT: randomized controlled trial.