The ‘Hidden’ Cholesterol That Could Raise Heart Attack and Stroke Risk Even With Low LDL

For decades, cholesterol has largely been divided into two categories: HDL, commonly known as “good” cholesterol, and LDL, or “bad” cholesterol.

But researchers are increasingly focusing on another form that could play a significant role in cardiovascular disease.

Known as remnant cholesterol, it is the cholesterol left behind from certain fat-carrying particles in the bloodstream after HDL and LDL have been accounted for. Growing evidence suggests that elevated levels could increase the risk of heart attacks and strokes, even among people whose LDL readings appear healthy.

What Is Remnant Cholesterol?

Remnant cholesterol develops during the breakdown of triglyceride-rich particles in the bloodstream.

Triglycerides are a type of fat used by the body for energy or stored in fat tissue. They travel through the bloodstream inside lipoproteins, which contain only a small amount of cholesterol.

When the triglycerides are removed from these particles, the remaining cholesterol is referred to as remnant cholesterol.

Although the cholesterol component is relatively small, the particles carrying triglycerides can be considerably larger than LDL or HDL particles. This means the amount of cholesterol left behind can still become substantial.

Why High Levels May Be Dangerous

Like LDL, remnant cholesterol appears capable of contributing to the buildup of deposits inside artery walls.

These deposits can promote inflammation and narrowing of the arteries, increasing the possibility of blockages that may eventually trigger a heart attack or stroke.

Professor Kausik Ray of Imperial College London has warned that remnant particles may be particularly harmful once they enter the artery wall, potentially producing greater inflammation than LDL.

Researchers are therefore questioning whether conventional cholesterol assessments always provide the complete picture of a person’s cardiovascular risk.

Studies Link Remnant Cholesterol to Major Cardiovascular Events

Evidence supporting the concern has grown considerably in recent years.

A 2021 study involving about 17,000 adults, conducted by researchers at Johns Hopkins University, found that people with high remnant cholesterol faced up to a 50 per cent greater risk of heart attack or stroke, including people whose LDL cholesterol was low.

More recent research involving more than 40,000 people by the Chinese Academy of Medical Sciences in Beijing produced an even stronger warning. Participants with elevated remnant cholesterol were found to have roughly three times the risk of suffering a heart attack or stroke over 10 years compared with those with much lower levels.

Researchers believe these findings indicate that remnant cholesterol deserves greater attention when cardiovascular risk is assessed.

A Hidden Risk Despite ‘Healthy’ LDL Levels

One of the biggest concerns is that someone can receive a reassuring LDL result while still having elevated remnant cholesterol.

A 2024 study from Changi General Hospital in Singapore found that about 11 per cent of people with healthy LDL levels nevertheless had remnant cholesterol readings considered potentially dangerous.

Because remnant cholesterol is not routinely included in standard cholesterol testing, these individuals may not realise they have another potential cardiovascular risk factor.

Experts are consequently calling for greater attention to other measurements, particularly triglycerides.

Statins May Not Reduce Remnant Cholesterol as Much

The issue is further complicated by the way cholesterol-lowering medication works.

Statins are widely prescribed to reduce LDL cholesterol and are taken by more than eight million people in the UK. However, their impact on remnant cholesterol appears to be less pronounced.

Professor Ray said statins can typically reduce LDL levels by around 50 per cent, while reducing remnant cholesterol by approximately 30 per cent.

This does not mean statins are ineffective or should be stopped. Rather, it highlights why some patients may require a broader approach to managing their cardiovascular risk.

Triglycerides Could Provide an Important Clue

There is currently no routine requirement for standard cholesterol tests to directly measure remnant cholesterol.

However, doctors already measure triglycerides, which are closely associated with the particles responsible for carrying remnant cholesterol.

The British Heart Foundation considers a triglyceride level below 1.7mmol/l healthy when measured after fasting for at least 10 hours. For a non-fasting test, the healthy level is below 2.3mmol/l.

Elevated triglycerides could therefore indicate that a person needs a closer assessment of their overall cardiovascular risk.

Experts Call for More Attention to Triglyceride Levels

Professor Ray believes triglyceride results should receive greater consideration when doctors assess patients for cardiovascular disease.

He has suggested that people with high triglycerides may need more intensive treatment, potentially involving higher statin doses or an additional medication aimed at lowering their levels.

The appropriate treatment, however, depends on an individual’s overall health and cardiovascular risk and should be determined by a medical professional.

Lifestyle Changes Can Also Make a Difference

Medication is not the only potential way to address high triglycerides and remnant cholesterol.

Dietary changes can help bring triglyceride levels down. Professor Ray recommends paying particular attention to carbohydrates and saturated fat, with their combined intake managed carefully as part of the overall diet.

The emerging research does not overturn the importance of controlling LDL cholesterol. Instead, it suggests that cardiovascular health may be more complicated than the traditional “good versus bad” cholesterol explanation.

The Bigger Picture for Heart Health

The growing focus on remnant cholesterol is prompting researchers to look beyond a single number on a standard cholesterol test.

LDL remains an important target because of its established role in artery disease, while HDL and triglycerides also provide valuable information. But elevated remnant cholesterol could represent an additional risk that is currently overlooked in some patients.

With studies increasingly linking high levels to heart attacks and strokes, experts believe the lesser-known form of cholesterol may deserve a much bigger role in future cardiovascular risk assessments.