In a recent study published within the journal Current Medical Research and Opinion, researchers report that top lipoprotein(a) levels were linked to repeated coronary heart disease events in older adults.

Study: Lipoprotein(a) and the chance of recurrent coronary heart disease: the Dubbo Study. Image Credit: SUWIT NGAOKAEW / Shutterstock.com

Background

The lipoprotein(a) structure consists of a low-density lipoprotein (LDL) structure attached to a glycoprotein apolipoprotein. Recent studies indicate that top levels of lipoprotein(a) contribute to aortic valve disease and atherosclerotic heart problems.

Lipoprotein(a) is believed to be the same risk factor as LDL for heart problems and mortality. Subsequently, by reducing lipoprotein(a) levels, patients could also be at a reduced risk for future cardiovascular events.

A previous study by the identical authors demonstrated the link between lipoprotein(a) levels and the occurrence of coronary heart disease amongst adults in Australia above the age of 60 years, with a follow-up of 16 years. Inside the top quartile of lipoprotein(a) distribution, there was a forty five% excess risk in the primary presentation of coronary heart disease. Nonetheless, only recently have studies examined the connection between increases in lipoprotein(a) levels and the potential of recurrent heart problems.           

Concerning the study

In the current study, researchers invited the participants from their first study, often known as the Dubbo study, to take part in the second study examining the association between elevated levels of lipoprotein(a) and the chance of repeated coronary heart disease events.

Baseline observations for demographic, cardiovascular, and psychosocial risk assessments were recorded. A spread of medical assessments was performed, including blood tests, anthropometry, resting electrocardiogram, and blood pressure. Blood samples were collected after 12 hours of fasting to measure glucose, lipoproteins, and lipids levels.

Prevalent coronary heart disease on the onset of the study was defined as previous angina or myocardial infarction—resting electrocardiogram changes recorded throughout the baseline measurements.

Incident coronary heart disease events that would have occurred over the 16 years between the primary and second study were determined from records for hospitalization or death and postal surveys that were conducted to verify the vital status of the patient every two years.

A modified enzyme-linked immunosorbent assay (ELISA) called sandwich ELISA was used to measure the degrees of lipoprotein(a). LDL levels of cholesterol were also determined and corrected for the cholesterol content from lipoprotein(a).

The Cox proportions hazard regression model was used to find out the independent association between elevated lipoprotein(a) levels and recurrent coronary heart disease.

Study findings

A complete of 399 cases of coronary heart disease with median lipoprotein(a) levels of 130 mg/liter were included in the present study. Comparatively, the median lipoprotein(a) levels in cases with no recurrent coronary heart disease were 105 mg/liter. The difference between the lipoprotein(a) levels of people with and without recurrent coronary heart disease was mildly significant.

Other significant differences between those with and without recurrent coronary heart disease included older age, male gender, low high-density lipoprotein (HDL) levels of cholesterol, and high triglyceride levels. Moreover, many recurrent coronary heart disease cases used anti-hypertensive therapies, atrial fibrillation, or diabetes. LDL levels of cholesterol weren’t higher in individuals with recurrent coronary heart disease events.

The distribution of lipoprotein(a) levels was highly skewed, which led to identifying individuals with elevated lipoprotein(a) levels and using multivariate models to discover their relative risk of coronary heart disease.

To this end, for people with lipoprotein(a) levels higher than 300 mg/liter, the excessive relative risk was 37% as in comparison with individuals with lipoprotein(a) levels lower than 300 mg/liter. Similarly, for people with lipoprotein(a) levels higher than 500 mg/liter, the relative risk increased to 59% compared to those with lipoprotein(a) levels lower than 500 mg/liter.

Notably, the concentration of LDL after correcting for the 30% lipoprotein(a) derived cholesterol within the body was not a predictor of coronary heart disease on this study.

Conclusions

High levels of lipoprotein(a) were a risk factor for recurrent events of coronary heart disease amongst individuals above the age of 60 years. For people with lipoprotein(a) levels of 355 mg/liter or greater, the potential of one other coronary artery disease event was 53% higher.

While the impact of treatments that deal with lowering lipoprotein(a) levels to limit the incidence of recurrent coronary heart disease stays unclear, the present study reported that low-density lipoprotein levels didn’t predict the chance of recurrent cardiovascular events.