Effectiveness of a low-intensity telephone counselling intervention on an untreated metabolic syndrome detected by national population screening in Korea: a non-randomised study using regression discontinuity design

OBJECTIVE: Whether low-intensity telephone-counselling interventions can improve cardiometabolic risk factors in screen-detected people with metabolic syndrome (MetS) is unclear. The aim of this study was to evaluate the effectiveness of a low-intensity, telephone-counselling programme on MetS implemented by the National Health Insurance Service (NHIS) of Korea using regression discontinuity design. DESIGN: A nationwide non-randomised intervention study with a regression discontinuity design. A retrospective analysis using data from NHIS. SETTING: NHIS, Korea from January 2011 to June 2013. PARTICIPANTS: 5 378 558 beneficiaries with one or more MetS components by NHIS criteria detected by population screening were enrolled in the NHIS MetS Management Programme in 2012. Of these, 1 147 695 underwent annual follow-up examinations until June 2013 (‘control group’ which received control intervention, n=855 870; ‘eligible group’ which was eligible for counselling, n=291 825; ‘intervention group’ which participated in telephone counselling among eligible groups, n=23 968). MAIN OUTCOME MEASURES: Absolute changes in MetS components, weight and body mass index (BMI) were analysed. Multiple regression analyses were applied using the analysis of covariance model (baseline measurements as covariates). RESULTS: Low-intensity telephone counselling was associated with decreased systolic BP (−0.85 mm Hg, 95% CI −1.02 to −0.68), decreased diastolic BP (−0.63 mm Hg, −95% CI −0.75 to −0.50), decreased triglyceride (−1.57 mg/dL, 95% CI −2.89 to −0.25), reduced waist circumference (−0.09 cm, 95% CI −0.16 to −0.02), reduced weight (−0.19 kg, 95% CI −0.24 to −0.15) and reduced BMI (−0.07 kg/m(2), 95% CI −0.09 to −0.05), when comparing the intervention and control groups. When individuals with low high-density lipoprotein cholesterol were analysed, the intervention was also associated with increased HDL cholesterol (0.90 mg/dL, 95% CI 0.51 to 1.29). CONCLUSIONS: Low-intensity telephone counselling programmes could yield improvements in the following year on blood pressure, lipid profiles, weight and body mass index in untreated patients detected at the population screening. However, the improvements may be very modest and the clinical relevance of these small improvements may be limited.