Aim: Most epidemiologic studies that have evaluated coronary risk factors have measured either mortality or morbidity of coronary artery disease (CAD) as endpoints. However, earlier detection and elimination of coronary risk factors are crucial. We therefore performed Master's double (i.e. 1.5 min x 2 = 3 min) two-step exercise electrocardiograph (ECG) test in apparently healthy asymptomatic subjects (men, n = 2274; women, n = 959) to elucidate the risk factors for early-stage CAD or silent myocardial ischemia.
Methods: We examined the possible association of blood pressure at health screening and other suspected risk factors with exercise ECG test performance. The ischemic ECG response was determined by (1) > or = 0.5 mm horizontal or sagging S-T segment depression, (2) > or = 2.0 mm J-shaped S-T segment depression, or (3) T inversion in post-exercise ECG.
Results: We found that 4.7% of men and 10.6% of women exhibited ischemic responses. Among males, the ischemic responders to the exercise ECG test had higher systolic and diastolic blood pressure. In addition, the male ischemic responders were older, had a higher obesity index, higher serum cholesterol, triglyceride, low-density lipoprotein (LDL)-cholesterol, protein, glucose, and uric acid levels, and a lower serum potassium level than normal responders. In contrast, the female ischemic responders to the exercise ECG test had higher systolic pressure, and higher serum cholesterol, LDL-cholesterol, and protein levels than normal responders. Mean blood pressure was correlated positively with most of the other coronary risk factors, and mild hypertensives and hypertensives had abnormal lipid, glucose, and uric acid levels in both sexes. A comparison of risk factors by age group revealed that only younger and middle-aged ischemic responders had higher blood pressure, serum cholesterol, and glucose levels than normal responders of both sexes, and that in older subjects all the differences between normal and ischemic responders became insignificant.
Conclusions: Elevated blood pressure at health screening, together with abnormal lipid and glucose metabolism, might be risk factors predicting early-stage or silent CAD. The elimination of these risk factors in younger men and women seems to be important.