Variant of ‘bad’ cholesterol especially harmful for older adults’ hearts, study warns

SYDNEY — A form of “bad cholesterol” in the bloodstream could pose a risk for recurrent heart problems in people over 60. That’s the conclusion of a recent study spanning 16 years out of the University of New South Wales Sydney.

High cholesterol levels in the blood contribute to the risk of coronary heart disease (CHD). Cholesterol is transported in the blood by lipoproteins, which consist of protein and fat. Lipoproteins include low-density lipoprotein (LDL), high-density lipoprotein (HDL), and Lipoprotein(a), or Lp(a), a variant of LDL cholesterol. Of course, LDL cholesterol is commonly referred to as “bad cholesterol” because it accumulates in blood vessel walls, increasing the likelihood of cardiovascular disease. Lifestyle changes and medications such as statins can help bring cholesterol levels within a healthy range.

Study authors reveal that increased levels of Lp(a) in the bloodstream pose a risk for recurrent coronary heart disease (CHD) in individuals aged 60 or above. The findings suggest that current cholesterol-lowering medications may not effectively reduce the risk of recurring CHD events, such as heart attacks, caused by elevated Lp(a).

“This finding adds to growing evidence of a relationship between increased Lp(a) and the risk of recurrent coronary heart disease,” says lead study author Leon Simons, an associate professor at the school, in a media release.

Simons explains that those who have already experienced CHD are at a high risk of experiencing another event. The study indicates that new therapeutics aimed at reducing elevated Lp(a) might help prevent recurrent disease. However, the clinical benefits of such therapy are yet to be confirmed.

CHD is the most common type of heart disease, characterized by the narrowing of arteries that supply oxygen-rich blood to the heart. It is a leading cause of heart attacks and the primary cause of death globally for both men and women in 2019.

While previous research has linked high Lp(a) levels to the development of coronary heart disease, most studies have focused on the association between Lp(a) levels and the risk of a first CHD event. This study examined whether elevated Lp(a) is predictive of a second or recurrent CHD event.

The research involved 607 Australians aged 60 and above, all with pre-existing CHD, who were followed for 16 years as part of the Dubbo study, with 399 incident CHD cases. Among the study’s findings:

• Individuals who experienced recurrent CHD had a median Lp(a) level of 130 mg/L, compared to 105 mg/L in those who did not.
• 26% of individuals with recurrent CHD and 19% of those without had Lp(a) levels exceeding 300 mg/L.
• 18% of individuals with recurrent CHD and 8% of those without had Lp(a) levels surpassing 500 mg/L.
• In older individuals with previous CHD, elevated Lp(a) levels in the top 20% of the population distribution (>355 mg/L) predicted a 53% higher risk of recurrent CHD events compared to those in the lowest 20% of the population distribution (<50 mg/L) over the 16-year follow-up period. This prediction was independent of other risk factors.

“We conclude that elevated Lp(a) is an important predictor of recurrent CHD in older people. Upper reference Lp(a) levels of 500 mg/L or 300 mg/L both appear to be appropriate for identifying those at higher risk who may benefit from more intensive risk reduction interventions,” Simons explains. While current medications like statins are often prescribed to lower “bad cholesterol” in patients at higher risk of cardiovascular disease, they do not have a significant impact on elevated Lp(a). However, there is hope for the future, as some novel therapeutics designed to lower Lp(a) levels are currently in the advanced stages of clinical development.

It’s important to note that this study’s baseline data were collected in 1988-89, and other factors, such as the use of statin therapy, may have influenced CHD risk over the years of follow-up. Nonetheless, it can be reasonably assumed that individuals with elevated Lp(a) at the beginning of the study maintained that status throughout the entire period.

The study is published in the journal Current Medical Research and Opinion.