Postal reminder with reduced burden of clinic information seeking for equitable participation in general health...

High participation rate and low inequality in participation are key to the program success of general health check-ups in Japan. This study examined the effectiveness of a postal reminder including nearest clinic information, compared to the standard postal reminder including details of all local clinics, on participation rate and income-based participation rate in general health checks. This was a single-blind, two-arm, prospective, randomized controlled study conducted at the Fukuoka Branch of Japan Health Insurance Association. Dependents (family members) of insured persons aged 40-69 years were randomly assigned (1:1) to the intervention group that received a tailored postal reminder intervention (showing information on the nearest clinic from each participant's address) or to the control group that received an original template postal reminder (containing just the URL of the website listing all available clinics). Allocation was concealed from participants and service providers of general health check-up. The primary outcome was participation in general health check-ups within 1 month of intervention. Between February 1 and February 10, 2017, 21,017 were randomly assigned to the intervention (n = 10,474) or control (n = 10,543) group. The participation rate in the intervention group was higher than control group (3.2% vs. 2.1%; OR: 1.55, 95% CI: 1.31-1.85, P < 0.001). The intervention effect was estimated to decrease as the income category increased (P for interaction = 0.037). Tailored postal reminders with information on the nearest clinic were able to improve the overall participation rate and reduce income-based inequality in participation for general health check-ups in Japan. Trial registration: UMIN-CTR, UMIN000042509, Registered 26 November 2020 - Retrospectively registered.