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Would people at low risk of heart disease benefit from statin treatment?

Thursday 17 October 2019

"Benefits of statins 'are marginal at best' for otherwise healthy people," reports the Mail Online.

Statins, which reduce levels of LDL ("bad") cholesterol in the blood, are medicines that are widely used to prevent heart attacks and strokes.

Heart attacks and strokes can happen in people who have cardiovascular disease (disease of the heart and blood vessels). Previous research shows that statins reduce the risk of a second heart attack or stroke in people who have cardiovascular disease.

However, people who do not have a previous history of cardiovascular disease can be offered statins to try to prevent them having a heart attack or stroke. This is called primary prevention. But there is uncertainty about whether the benefits of statins outweigh the risks for everyone in this group of people.

In the UK, the National Institute for Health and Care Excellence (NICE) says that people can be offered a statin if their risk of getting cardiovascular disease in the next 10 years is 10% or more. Their risk is measured using a risk calculator that looks at factors such as cholesterol level, age, smoking and blood pressure.

In a new study, researchers from Ireland looked at the evidence for statins in people who do not already have cardiovascular disease. Most studies showed statins reduced the risk of having or dying from a heart attack or stroke, compared to people who did not take statins.

But the researchers say the absolute benefit or risk depends on each person's own health and risk factors (baseline characteristics).

The researchers conclude that people being offered statins should be given more information about their individual chances of benefiting from the drugs, and of possible side effects, such as muscle and joint pain.

Find out more about statins for cardiovascular disease.

Where did the story come from?

The researchers who carried out the study were from the National University of Ireland Galway, and the Royal College of Surgeons Dublin – General Practice.

The study was published in the peer-reviewed British Medical Journal and is openly available to access online.

The Sun, Daily Telegraph and Mail Online covered the story, questioning the benefit of statins for people at low risk. They all cited an example from the study of a woman with a 1.4% risk of cardiovascular disease in the next 10 years, saying she would get only a tiny benefit from statins.

But this is not a particularly useful or relevant example. Someone with this level of risk would not be offered statins on the NHS, as her risk is well below the 10% baseline set out in NICE guidelines.

What kind of research was this?

This appears to be a non-systematic review where the researchers discuss the use of statins for primary prevention and guideline recommendations around their use. They then give a general overview of the findings from previous systematic reviews.

The main limitation is that the researchers have not clearly described their search methods, study inclusion and exclusion criteria and quality appraisal. This means we cannot know for sure that this is a comprehensive review of all relevant literature on the risks and benefits of statins for primary prevention in people without existing cardiovascular disease.

The study authors describe that this article builds on several previous papers they have published. But without more detail about their search methods, such an approach leaves them open to accusations of "cherry picking" – only including evidence that supports their argument.

What did the research involve?

The researchers reported on their previous study about the effects of changing guidelines on the numbers of people in Ireland eligible to be prescribed statins.

Then they looked at 3 previous systematic reviews of statins in people who did not have cardiovascular disease. They calculated the benefit of statins according to people's risk of cardiovascular disease, and used results from another review to contrast the potential benefits for people at low and high risk of cardiovascular disease.

The researchers then reported on the controversy around possible side effects of statins, and the calls there have been in the past for more data to be released about this from big statin trials.

Finally, they questioned whether people were being given enough information to make an informed choice about the risks and benefits for them of taking a statin.

What were the basic results?

The researchers (based in Ireland) reported that changes in European guidelines resulted in 61% of Irish adults over 50 being eligible for statin treatment in 2016, compared to 8% in 1987.

From analysis of 3 reviews looking at primary prevention of cardiovascular disease, they found:

  • a 9% reduction in risk of death for those taking statins (relative risk (RR) 0.91, 95% confidence interval (CI) 0.85 to 0.97)
  • a 29% reduction in risk of heart attack (RR 0.71, 95% CI 0.65 to 0.77)
  • a 25% reduction in risk of stroke (RR 0.75, 95% CI 0.70 to 0.80)
  • a 15% reduction in risk of death from heart attack or stroke (RR 0.85, 95% CI 0.77 to 0.95).

However, they said the benefit for each individual depended on their own personal risk of cardiovascular disease. That's because the difference a "relative risk reduction" makes depends on the size of the person's risk to start with.

The researchers give the example from one review of a 65-year-old man who does not have cardiovascular disease but who smokes, has high cholesterol and high blood pressure.

He has a 38% risk of heart attack in the next 10 years (this is the baseline risk). The relative risk reduction would give the man a 9% absolute reduction in his personal risk of heart attack, putting it at around 29%.

However, if you take an example of a 45-year-old woman who has raised cholesterol but no other risk factors, her baseline risk of cardiovascular disease is lower, at 1.4%. The absolute benefit she'd get from taking a statin is about a 0.6% absolute risk reduction, so her risk would only fall from 1.4% to 0.8%.

The researchers also found that if you look at the overall data from the studies divided into risk levels (people with less than 5% overall risk, 5% to 10%, 10% to 20% and so on) then the relative reductions in risk look much less certain and in some cases are not statistically significant.

However, this may simply be because dividing the data up means smaller groups, and statistics are less certain when you have smaller groups to work with.

The researchers said that previous studies have found increased risk of some rare but serious side effects (to do with breakdown of muscles), and that milder side effects are uncertain.

How did the researchers interpret the results?

The researchers said their review showed that: "Although statins are commonly prescribed, serious questions remain about their benefit and acceptability for primary prevention, particularly in patients at low risk of cardiovascular disease."

They said statins may be "an example of low value care" for low risk patients and could "represent a waste of healthcare resources".

Conclusion

This study shows us that changes in European guidelines have resulted in more people in Ireland being eligible for statins. There are likely to have been similar rises in eligibility in the UK, since NICE lowered the cardiovascular risk threshold for statin treatment from 20% to 10% over 10 years in 2014.

The analysis of studies demonstrated what was already known – that statins provide a modest reduction in risk of cardiovascular disease for people who have not had a previous heart attack or stroke.

It also demonstrates the important point that people's potential to benefit from statin treatment depends on their personal baseline risk of cardiovascular disease.

In the UK, GPs use a standard risk calculator to assess people's risk based on a number of factors including age, ethnic background, blood pressure and cholesterol levels.

People who have a 10% or higher risk may be offered statins, as statins could make a meaningful difference to their risk of having a heart attack or stroke.

But for people who have raised cholesterol but no other risk factors – like the 1.4% risk example quoted by the media – there would be little benefit from starting statin treatment. Therefore statins would not usually be recommended for these low-risk individuals.

People with a 10% baseline risk do not have to take statins. The decision is for people to take in discussion with their GP, along with other considerations such as diet, weight loss and exercise.

The main limitation with this research, as discussed, is that unfortunately the study authors give no methods as to how they have identified and selected the reviews included in their paper. Therefore we do not know for certain that these show the full picture of evidence.

The best option is for anyone concerned about taking statins to discuss their potential risk and benefit with their GP.

You can also lower your risk of cardiovascular disease through things such as healthy eating, regular exercise, sticking to the recommended alcohol limits and stopping smoking.

Analysis by Bazian
Edited by NHS Website