Statin là gì? Và những người khỏe mạnh có nên sử dụng chúng để phòng ngừa bệnh tim và chứng mất trí nhớ không?

Every month, around 2.7 million Australians have a statin dispensed to lower their risk of heart attack and stroke.

Statins reduce the risk of cardiovascular disease, the collective term for conditions involving the heart and blood vessels.

Now, two recent studies have investigated if statins could be used preventatively in healthy people – to protect against dementia and promote healthier ageing. Let’s take a look at the evidence.

What are statins?

Statins have been used for decades to reduce the amount of cholesterol the liver produces. This lowers low–density lipoprotein (LDL) in the blood, sometimes called “bad” cholesterol.

High levels of LDL can contribute to fatty deposits called plaques in artery walls. This build up is known as atherosclerosis.

When a plaque ruptures, a blood clot can block blood flow in the artery. This can cause a heart attack or stroke.

For most people, statins are well tolerated. But like all medicines, they can cause side effects. Sometimes people report muscle aches or cramps, but rarely do they cause serious muscle injury.

Why are ‘healthy’ people prescribed statins?

Statins are often prescribed after someone has a heart attack or stroke. But they can also be prescribed to “healthy” people who have never experienced either but have high cholesterol and other risk factors.

Many factors contribute to heart attack and stroke risk, not just cholesterol levels. These include your age, blood pressure and whether you smoke, and your medical history, for example, whether you have diabetes and chronic kidney disease.

Risk calculators have been developed that combine all of these factors to estimate someone’s overall chance of experiencing a heart attack or stroke (cardiovascular event) within the next five years.

In Australia, cholesterol-lowering medicines are recommended for people at high risk of cardiovascular disease and may also be considered for people at intermediate risk.

But the cardiovascular disease risk calculator only applies to people up to 79 years of age. Why? Because until recently, evidence for starting statins in older people without a previous heart attack or stroke was limited.

Recently, research has investigated whether statins might also reduce some forms of cognitive decline or dementia by preventing blood vessel damage in the brain.

So, do statins really reduce dementia risk?

A recent Danish study involving more than 132,000 people with type 2 diabetes found that starting statins within one year of diagnosis was linked to a 15% lower relative risk of dementia, compared to non-users.

However, this was an observational study, meaning they researched what was happening in the real world rather than in a controlled trial. As a result, there are many potential sources of bias that could have influenced the findings.

For example, the group who were using statins in this study were younger than those who didn’t. They had a lower risk of developing dementia, simply because of their age.

This means the group that used the medicine and the group that didn’t already had important differences in their dementia risk. This can cause a bias in the evidence known as confounding by indication.

There is also the issue of healthy user bias. People who take statins may be more health conscious and more likely to take preventative health measures. So they may be at lower risk of dementia, independent of their statin use.

Additionally, dementia is a condition that develops gradually. Early cognitive decline may go undiagnosed. Cognitive decline could also make someone less likely to start or continue long–term preventive medicines.

This could make it seem like statin use is protecting against dementia, when it may actually be that people with dementia are less likely to use statins. This is known as reverse causality.

Importantly, this study only included people with type 2 diabetes. The findings cannot automatically be applied to people without diabetes.

Do statins help with healthy ageing?

Another recent study, run by researchers at Monash University, investigated the effects of starting statins in almost 10,000 people aged 70 years and older.

These researchers used a randomised controlled trial design to try to address some of the issues with bias.

The study investigated whether atorvastatin (a commonly prescribed statin) could reduce serious cardiovascular events such as heart attack and stroke in otherwise healthy older people. This means they didn’t have pre-existing cardiovascular disease.

The researchers also examined whether it could extend “disability–free survival”. This means living without dementia or persistent physical disability.

To remove the potential of selection bias and healthy user bias, they randomised participants to receive either atorvastatin or placebo. They also only included older people who had not used statins previously, so they started the trial with a similar risk profile.

The study found that after around six years, atorvastatin reduced the risk of a first major heart attack or stroke by 30%. However, it did not prolong disability–free survival.

Randomised controlled trials can help address bias, but they can still have limitations. For example, in this study, participants were relatively healthy and living independently.

This means that the findings may not apply as readily to older, frail people, or those who take multiple medicines or have multiple medical conditions.

So, should I start a statin?

The new evidence broadens our understanding of who might benefit from statins. But it doesn’t mean everyone should take one.

Remember, every medicine comes with both risks and benefits. Deciding on whether a statin is right for you will depend on your individual risk – and is a decision best made with your doctor.

Jack Janetzki works for Adelaide University, Pharmaceutical Defence Limited and The Barossa Pharmacist in the Mall (Nuriootpa, South Australia) . He is a human research ethics committee member for Bellberry Ltd, a member of Pharmaceutical Defence Limited, the Pharmaceutical Society of Australia, the Australian Health Data Evidence Network (AHDEN) and the Observational Health Data Science and Informatics (OHDSI) network.

Nicole Pratt receives funding from the National Health and Medical Research Council and the Medical Research Future Fund.

Lauren Cortis does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.