High Level of Estimated Small Dense Low-Density Lipoprotein Cholesterol as an Independent Risk Factor for the Development of Ischemic Heart Disease Regardless of Low-Density Lipoprotein Cholesterol Level - A 10-Year Cohort Study.

Background: We previously reported that a high level of small dense low-density lipoprotein cholesterol (sdLDL-C) calculated by the Sampson equation was independently associated with the development of ischemic heart disease (IHD), but it remains unclear whether the effect depends on the level of low-density lipoprotein cholesterol (LDL-C).

Methods and results: We investigated the associations of new onset of IHD with categorized groups of high (H-) and low (L-) levels of estimated sdLDL-C and LDL-C using 25^thpercentile levels of sdLDL-C level (25.2 mg/dL) and LDL-C (100 mg/dL) as cutoff values in 17,963 Japanese individuals (men/women: 11,508/6,455, mean age: 48 years) who underwent annual health checkups. During a 10-year follow-up period, 570 subjects (men/women: 449/121) had new development of IHD. Multivariable Cox proportional hazard analyses after adjustment of age, sex, smoking habit, hypertension and diabetes mellitus at baseline showed that the hazard ratio (HR) [95% confidence interval (CI)] for new onset of IHD was significantly higher in subjects with H-sdLDL-C/H-LDL-C (1.49 [1.06-2.08]) and subjects with H-sdLDL-C/L-LDL-C (1.49 [1.00-2.22]) than in subjects with L-sdLDL-C/L-LDL-C as the reference.

Conclusions: A high level of sdLDL-C estimated by the Sampson equation was a predominant predictor for the development of IHD, regardless of the level of LDL-C, in a general Japanese population.