Total cholesterol and mortality from ischemic heart disease and overall cardiovascular disease in Korean adults

It is not completely clear whether "the lower, the better" cholesterol hypothesis for cardiovascular disease (CVD) and ischemic heart disease (IHD) can be applied to general populations with a low risk of heart disease mortality. We prospectively followed up 503,340 Koreans who participated in routine health checkups during 2002-2003 until 2013 via linkage to national mortality records. Nonlinear associations with total cholesterol (TC) were found: U-curves for overall CVD (I00-I99; nadir at 180-200mg/dL) and a reverse-L-curve for IHD (I20-I25). Assuming a linear association in the lower range (< 200mg/dL), TC was inversely associated with CVD mortality (HR per 39mg/dL [1 mmol/L] increase= 0.90). In the upper range (200-349mg/dL), TC was positively associated with CVD mortality, largely due to IHD (HR= 1.19), especially acute myocardial infarction (HR= 1.23). The associations were generally similar in men versus women and in middle-aged (40-64years) versus elderly (>= 65 years) adults. TC levels of 180-200mg/dL were associated with the lowest CVD mortality. Below 200mg/dL, TC had no graded positive associations with IHD mortality. It remains unclear whether the lowest cholesterol levels are associated with the least mortality from CVD and IHD in Korean adults with a low risk of heart disease.