Association of the National Health Guidance Intervention for Obesity and Cardiovascular Risks With Health Outcomes Among Japanese Men

IMPORTANCE: Obesity and cardiovascular risks have become major public health problems. However, evidence is limited as to whether population-level lifestyle interventions for obesity and cardiovascular risk factors are associated with improved population health outcomes. OBJECTIVE: To investigate the association of the national health guidance intervention in Japan with population health outcomes. DESIGN, SETTING, AND PARTICIPANTS: This cohort study used a regression discontinuity design that included men aged 40 to 74 years who participated in the national health screening program in Japan from April 2013 to March 2018. EXPOSURES: Assignment to the national health guidance intervention (counseling on healthy lifestyle and appropriate clinical follow-up for individuals found to have waist circumference of 85 cm or greater with 1 or more cardiovascular risk factors during annual national health screening program). MAIN OUTCOMES AND MEASURES: Changes in obesity status (body weight, body mass index, waist circumference), and cardiovascular risk factors (blood pressure, hemoglobin A(1c) level, and low-density lipoprotein cholesterol level) 1 to 4 years after screening. RESULTS: Of 74 693 men (mean [SD] age, 52.1 [7.8] years; mean [SD] baseline waist circumference, 86.3 [9.0] cm), the assignment to the health guidance intervention was associated with lower weight (adjusted difference, −0.29 kg; 95% CI, −0.50 to −0.08; P = .005), body mass index (−0.10; 95% CI, −0.17 to −0.03; P = .008), and waist circumference (−0.34 cm; 95% CI, −0.59 to −0.04; P = .02) 1 year after screening. The observed association of the guidance assignment attenuated over time and was no longer significant by years 3 to 4. No evidence was found that the health guidance intervention was associated with changes in participants’ systolic blood pressure, diastolic blood pressure, hemoglobin A(1c) level, or low-density lipoprotein cholesterol level in years 1 to 4. CONCLUSIONS AND RELEVANCE: Among working-age men in Japan, the national health guidance intervention was not associated with clinically meaningful weight loss or other cardiovascular risk factor reduction. Further research is warranted to understand the specific design of lifestyle interventions that are effective in improving obesity and cardiovascular risk factors.