Researchers from Northwestern Medicine and Yonsei University pooled the health data of 9,341,100 South Korean adults, as well as 6,803 US adults, looking at four key risk factors: high blood pressure, cholesterol, blood-sugar levels and smoking. They found that – in both cohorts – more than 99% of people who suffered coronary heart disease (CHD) had problematic levels of at least one of the four risk factors.