Effect of the national lifestyle guidance intervention for metabolic syndrome among middle-aged people in Japan

Background Japan has implemented a national lifestyle guidance intervention programme for potential metabolic syndrome among adults aged 40-74 years; however, there is limited evidence regarding the causal impact of this intervention. The study aims to determine the causal effect of this intervention on health outcomes and health care utilisation. Methods We performed a regression discontinuity design study. A total of 46 975 adults with 21 cardiovascular risk factor in 2015 were included in the study. A two-stage evaluation process (stage 1: waist circumference 285 cm for men or 290 cm for women and 21 cardiovascular risk factor; stage 2: body mass index (BMI)225 kg/m2 and 22 cardiovascular risk factors) was applied. Changes in obesity, cardiovascular outcomes, and health care utilisation were evaluated in a one -year follow-up in the fiscal year 2016. Results Participants who received lifestyle guidance intervention based on the waist circumference had a statistically significant reduction in obesity outcomes (Delta weight: -0.30 kg, 95% CI = -0.46 to -0.11; Delta waist circumference: -0.26 cm, 95% CI = -0.53 to -0.02; Delta BMI = -0.09 kg/ m2, 95% CI = -0.17 to -0.04) but not in other cardiovascular risk factors and health care utilisation. Analyses based on BMI and results according to demographic subgroups did not reveal significant findings. Conclusions The provision of this intervention had a limited effect on health improvement and a decrease in health care costs, health care visits, and length of stay. A more intensive intervention delivery could potentially improve the efficacy of this intervention programme.