Small Dense Low-Density Lipoprotein Cholesterol and the Risk of Coronary Heart Disease in a Japanese Community

Small, dense LDL is a stronger signal for heart risk than total LDL

This Japanese community study followed 3,080 adults for about 8 years and found a clear, consistent pattern: people with higher levels of small dense LDL (sdLDL) cholesterol were much more likely to develop coronary heart disease (CHD), even when their overall LDL cholesterol was in the normal range.

Key Findings (in plain language)

• People in the highest sdLDL group had about a 5.4× higher risk of CHD than those in the lowest group, after accounting for age, blood pressure, diabetes markers, HDL, smoking, exercise, kidney function, and more.
• The risk was about doubled if sdLDL was ≥ 32.9 mg/dL (the study’s median), regardless of LDL levels. In other words, normal LDL did not guarantee low risk when sdLDL was high.
• Adding sdLDL to standard risk models improved prediction accuracy for future CHD events more than adding LDL did (c-statistic rose from 0.77 to 0.79, p = 0.02; with meaningful net reclassification improvement).
• A practical cutoff around 35–40 mg/dL for sdLDL identified a higher‑risk group in this Japanese population. Above 35 mg/dL, risk was ~2× higher after adjustments.

What this challenges

The data suggest that focusing on total LDL cholesterol alone can miss important risk, because sdLDL (the smaller, denser particles) appears more closely tied to future heart events. The study does not make dietary claims; it strictly shows that sdLDL carries independent risk beyond standard LDL and known factors.

Practical relevance for everyday people

• If you’ve been told your LDL is “normal”, this research indicates sdLDL could still matter for your heart risk. Or if your LDL is "high", sdLDL could be a better risk indicator.
• For those with diabetes or insulin resistance, sdLDL tended to be higher and was linked to risk, though the sdLDL–CHD association held regardless of diabetes status.
• sdLDL can now be measured with a routine lab assay; the study used an FDA‑cleared method and found it adds useful risk information.

A sensible way to gauge risk on keto

• Prioritize measuring ApoB and sdLDL (or LDL particle number/size by NMR). If ApoB is high and sdLDL ≥35–40 mg/dL, the Hisayama data and broader literature suggest higher atherogenic risk despite high HDL or low triglycerides.
• If LDL is high but ApoB is modest and sdLDL is low with predominantly large LDL particles, risk is likely lower than the LDL number implies, though long‑term outcomes are still unproven.