Lipoprotein(a) and cholesterol levels act synergistically and apolipoprotein A-I is protective for the incidence of primary acute myocardial infarction in middle-aged males. An incident case-control study from Sweden.

OBJECTIVE

To further establish the importance of total plasma apolipoprotein A-I and lipoprotein(a) in the prediction of primary acute myocardial infarction (AMI) in men.

DESIGN

An incident case-control study.

SETTING

The study was nested within the Västerbotten Intervention Program (VIP) and the Northern Sweden MONICA cohorts.

SUBJECTS

A total of 62 male AMI cases and 124 matched controls, randomly selected from the study cohorts.

RESULTS

In multivariate logistic regression, significant odds ratios (OR) were found for Lp(a) above 200 mg L-1, apo A-I below the mean value (1136 mg L-1) and total cholesterol (TC) above 7.8 mmol L-1. TC interacted significantly with Lp(a); for Lp(a) above 200 mg L-1 and TC below 6.5 mmol L-1, OR = 5.6; for Lp(a) above 200 mg L-1 and TC above 6.5 mmol L-1, OR = 12.6. To evaluate the potential effect of reducing high levels of Lp(a) or TC on the incidence of AMI in males, the attributable risk percentage (ARP) was calculated when interaction between the two variables was present. ARP is 31% for Lp(a) and 21% for TC, implying that 31% of the cases are due to high Lp(a) and 21% of the cases are due to high TC levels.

CONCLUSIONS

In the Swedish male population, total apo A-I in plasma is a protective factor and a plasma Lp(a) level above 200 mg L-1 is a risk factor for AMI in males. A TC level above 6.5 mmol L-1 increased the risk of AMI if the Lp(a) level was above 200 mg L-1, suggesting Lp(a) to be useful in identifying high risk individuals needed to be treated.