After last week’s controversial Catalyst program on the ABC, some people may be wondering whether they should stop taking statins to lower their cholesterol. But before making such a decision, read this article and discuss your risk of heart disease or stroke with a doctor.

About 2.6 million Australians take statins. And a recent analysis of Australian data found that over-treatment of people at low risk is more common than under-treatment of people at high risk.

This is problematic but it doesn’t reflect a problem with the statins. Rather, it shows that people may not be appropriately informed about who benefits from taking this medicine.

What the trials say

While Catalyst highlighted that most of the major trials for statins have been funded by the pharmaceutical industry, it didn’t explain their overall results.

A collaboration funded by the UK Medical Research Council, British Heart Foundation and Cancer Research UK (the Cholesterol Treatment Triallists Collaboration), brought together data from 26 trials involving 170,000 patients, to better understand what the trials found.

What they discovered was the results are remarkably consistent: they show statins reduce the risk of heart attack or stroke by about 20%. This is true whether you’ve had a heart attack or stroke in the past or not.

There were fewer women in the trials, so the numbers for women are less precise but they’re approximately the same as the overall numbers.

If your risk of having a heart attack or stroke over the next five years is 30%, taking statins will reduce it to 24%. If it’s 10%, your risk is reduced to 8%. Obviously, the benefit is greater if your initial risk is higher (we’ll come back to how to work this out later).

Heart attacks and strokes are serious events that most people want to avoid, and there’s clear, solid evidence that statins reduce the chance of having one.

But like all drugs, statins also have side effects and the Catalyst program was correct in pointing out that these were probably underestimated in the trials. There are good reasons for this.

Trials often exclude people with early side effects, the elderly and people with other conditions, such as kidney disease. It would be unethical to continue giving a new drug to someone if they are experiencing side effects and do not wish to continue, so participants can withdraw from the trial at any time.

The age group and medical conditions for clinical trials are specified so it can identify the effect of the drug on the target group for treatment. But the side effects of statins have been investigated in many other studies and populations outside of those trials, and continue to be monitored.

The most common side effects are fatigue, exercise intolerance, cataracts, and sometimes, memory loss. On the other hand, statins may protect people from small strokes that could cause dementia. This is why the decision to take statins has to be a balance between their benefits and risks.

Who should take statins

In Australia, the National Heart Foundation, Kidney Health Australia, Diabetes Australia, and the National Stroke Foundation (the National Vascular Disease Prevention Alliance) have weighed up the benefits and risks of drugs to lower cholesterol.

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They recommend medication for people who have a high absolute risk, which is more than a 15% chance of having a heart attack or stroke over the next five years.

The absolute risk of heart attack or stroke is calculated by using all the major factors that predict risk – age (it gets more likely as you get older), sex (males are at higher risk), blood pressure, and cholesterol. Whether someone smokes or has diabetes also strongly impacts their risk profile.

Medication may also be considered for people at moderate risk (10% to 15%), who haven’t been able to reduce their risk with diet and exercise. Or if they have a strong family history of heart disease.

The decision to take statins should not be based on someone’s cholesterol level alone unless it’s unusually high. If you are between 35 and 74 years of age, and know your blood pressure and cholesterol level, you can calculate your own risk here.

The advantage of this approach (using absolute risk as the guide) is that people at high risk of heart attack or stroke who have normal cholesterol levels can still reduce their risk by taking statins.

At the same time, people with mildly elevated cholesterol levels who have no other risk factors (and are therefore unlikely to benefit) don’t need to take them.

The balancing game

Regular exercise and a Mediterranean-style diet also lower the risk of heart attack and stroke, and are recommended for everyone, whether they have low, medium, or high risk. But for some people, this is not going to be enough.

The number of deaths from heart disease has fallen dramatically since its peak in the late 1960s and early 1970s. This is partly because of overall improvement of diet, efforts to stop smoking and control blood pressure.

But reducing cholesterol levels through drugs, such as statins, has also played an important role.

People on statins who are now questioning whether to continue take them should talk to a doctor about their absolute risk of heart attack or stroke. This calculation needs to be based on levels of cholesterol and blood pressure before starting medication.

If substantial lifestyle changes have recently been made, it may be appropriate to consider a trial period off statins.

Statins are no magic bullet and people who take them may still have a heart attack or stroke, even though their chance of having one is reduced. And the truth is that if a person has been taking statins and doesn’t have a heart attack or stroke, we can’t tell if that’s because of statins or because they were never going to have one.

The best we can do is use data from trials and other studies to estimate the benefits and risks. Like all medications, statins are not inherently good or bad - whether they help someone depends on whether their likely benefit outweighs their side effects for an individual.