[Effectiveness of letter and telephone reminders for specific health guidance use: A randomized controlled trial for those intending to use health guidance in a large city].

Objectives　Medical insurers have applied a reminder (i.e., recall) system to improve the implementation rate of specific health guidance. However, the effectiveness of the system has not been verified. This study aims to examine the effectiveness of two methods of specific health guidance reminders (i.e., letter and telephone) using a randomized controlled trial.Methods　Subscribers of National Health Insurance in Yokohama City, Kanagawa Prefecture, who were eligible for specific health guidance in 2020, were recruited. A specific health examination questionnaire was used to identify participants intending to use health guidance. The intervention period was from September to November 2020, with 252 people being randomly assigned to one of the three groups: a "no-reminder group," "a letter-reminder group," or "a telephone-reminder group" (84 people each). Those in the letter-reminder group received a reminder by mail and those in the telephone-reminder group received a reminder by phone from a public health nurse two weeks after the specific health guidance coupon was sent to the participants by mail. The outcome showed the utilization rate of specific health guidance. Chi-square tests were performed to compare the three groups and conduct multiple comparisons (post-hoc test).Results　The participants had a mean age of 61.4±11.0 years and 70.6% were male. There was no difference among the three groups in terms of demographic characteristics and the results of specific health examinations. The utilization rates of specific health guidance were 20.2% in the no-reminder group, 22.6% in the letter-reminder group, and 20.2% in the telephone-reminder group; thus, the three groups did not significantly differ (χ²=0.191, P=0.909). Multiple comparisons also showed no difference between any two groups. However, in the telephonereminder group, 56.0% of the participants themselves or their family members could be reached by a public health nurse, and their utilization rate was higher than those participants whom a public health nurse could not reach.Conclusion　Neither letter nor telephone reminders changed the participants' utilization rates of specific health guidance compared to those with no reminder. Although the effectiveness of a telephone reminder might be underestimated, this study suggests setting a lower priority in reminding those who intend to use health guidance.