Explaining the Decline in Coronary Heart Disease Mortality Rates in Japan: Contributions of Changes in Risk Factors and Evidence-based Treatments Between 1980 and 2012

Background: We aimed to quantify contributions of changes in risks and uptake of evidence-based treatment to coronary heart disease (CHD) mortality trends in Japan between 1980 and 2012.

Methods: We conducted a modelling study for the general population of Japan aged 35 to 84 years using the validated IMPACT model incorporating data sources like Vital Statistics. The main outcome was difference in the number of observed and expected CHD deaths in 2012.

Results: From 1980 to 2012, age-adjusted CHD mortality rates in Japan fell by 61%, resulting in 75,700 fewer CHD deaths in 2012 than if the age and sex-specific mortality rates had remained unchanged. Approximately 56% (95% uncertainty interval [UI]: 54-59%) of the CHD mortality decrease, corresponding to 42,300 (40,900-44,700) fewer CHD deaths, was attributable to medical and surgical treatments. Approximately 35% (28-41%) of the mortality fall corresponding to 26,300 (21,200-31,000) fewer CHD deaths, was attributable to risk factor changes in the population, 24% (20-29%) corresponding to 18,400 (15,100-21,900) fewer and 11% (8-14%) corresponding to 8400 (60,500-10,600) fewer from decreased systolic blood pressure (8.87 mm Hg) and smoking prevalence (14.0%). However, increased levels of cholesterol (0.28 mmol/L), body mass index (BMI) (0.68 kg/m), and diabetes prevalence (1.6%) attenuated the decrease in mortality by 2% (1-3%), 3% (2-3%), and 4% (1-6%), respectively.

Conclusions: Japan should continue their control policies for blood pressure and tobacco, and build a strategy to control BMI, diabetes, and cholesterol levels to prevent further CHD deaths.