High ApoB, Low ApoA-I, and the ApoB/ApoA-I Ratio as Predictors of Fatal Myocardial Infarction: The AMORIS Study

The AMORIS (Apolipoprotein-related MOrtality RISk) study was a large prospective cohort study that followed 175,553 Swedish subjects with baseline clinical chemistry measurements including ApoB and ApoA-I, recording 864 fatal MI events in men and 359 in women during follow-up.

ApoB was a stronger predictor of fatal MI than LDL-C in both sexes. ApoA-I — the principal structural protein of HDL — was inversely and independently associated with fatal MI risk. The ApoB/ApoA-I ratio was the single strongest predictor of fatal MI: the highest ratio quintile had approximately 4-fold greater risk of fatal MI than the lowest quintile in men, and the gradient was steeper than for any conventional lipid measure.

AMORIS represented one of the largest prospective datasets to directly compare apolipoproteins with conventional lipids for cardiovascular prediction at that time. Its key finding — that the balance between atherogenic (ApoB) and antiatherogenic (ApoA-I) particles is a more powerful predictor than absolute LDL-C — has been replicated in multiple subsequent large cohorts.

The ApoB/ApoA-I ratio captures both dimensions of lipoprotein risk simultaneously: the flux of atherogenic particles into the arterial wall (ApoB) and the flux of protective reverse-transport particles removing cholesterol from it (ApoA-I). A high ratio means many particles entering and few removing — a double atherogenic burden that LDL-C alone cannot characterize.

We rate the evidence strong. The landmark AMORIS prospective study in 175,553 subjects demonstrating that ApoB outperforms LDL-C for fatal MI prediction, and that the ApoB/ApoA-I ratio is the most powerful single lipid risk predictor — a foundational dataset for the apolipoprotein-based approach to cardiovascular risk assessment.