“Heart attack victims ‘should not give up taking statins’” reported The Times saying that people who have a heart attack and who give up taking statins afterwards double their risk of dying in the following year. The newspaper goes on to say that “even though the pills may appear to have failed to prevent a heart attack, it is much better to go on taking them anyway”.
This study used data on patients enrolled with GPs across the UK to investigate the effect of continuing or discontinuing statins in people who survived heart attacks and who were still alive three months later. These are potentially important findings, but they are based on a small subgroup of people (only 137 out of nearly 10,000) who stopped taking statins after their heart attack. The researchers themselves call for more research given the potential clinically important implications of this study.
Where did the story come from?
Dr Stella S. Daskalopoulou and colleagues from McGill University and the University of Washington carried out this study. Some of the researchers and their work were funded by Les Fonds de la Recherche en Sante du Quebec. Another researcher received the CIHR Distinguished Scientist Award. The study was published in the peer-reviewed medical journal: the European Heart Journal.
What kind of scientific study was this?
The study was a retrospective cohort study that followed up people in the UK who had survived a myocardial infarction (heart attack) between January 01 2002 and December 31 2004. They were identified using the General Practice Research Database (GPRD), which collects information on the health of more than three million people through 400 GP practices across the UK. The GPRD also collects information on demographics and lifestyle (height, weight, smoking, alcohol). This database is representative of the UK population and has been shown to be of high quality and is often used to study the population of the UK. Participants in this study were those who had survived at least 90 days after their first heart attack, were at least 20 years old, and had a minimum of three consecutive years of records in the database.
The participants were divided into four groups depending on their statin use around the time of their heart attack. These groups were: those who did not use statins 90 days before or after their heart attack; those who used statins before and after their heart attack; those who did not use statins before their heart attack but used them after; and those who used statins before their heart attack but did not use them afterwards.
The researchers compared the survival of the four groups (all causes of mortality) between 90 days and one year after the heart attack. In this way, they could investigate what effects different patterns of statin use around the time of a heart attack have on survival. They also took into account other factors that might have had an effect such as age, sex, smoking, alcohol, obesity, and number of hospitalisations. In total, 9,939 survivors were included in this study.
What were the results of the study?
Of the 9,930 survivors of their first heart attack, 2,124 had not used statins for 90 days before or after the event, 137 had been taking statins before but did not take them afterwards, 5,652 did not take statins before their event but took them afterwards, and 2,026 were taking statins both before and after.
Compared to people who never took statins, those who started taking them after their heart attack were less likely to die after one year. However, those who stopped statins after their heart attack were at increased risk of dying after one year. Those who took statins before and after their event were not statistically different from those who never took statins.
What interpretations did the researchers draw from these results?
The researchers say that their study suggests there is a strong harmful effect of stopping statins, and that those people who did not continue to take them after their heart attack were 88% more likely to die during the one year follow up (95% CI 1.13 to 3.07). This effect was not just due to stopping using a drug, as the same effect was not observed in people who stopped taking aspirin, beta blockers or PPIs.
What does the NHS Knowledge Service make of this study?
This large, population-based cohort study suggests that stopping statins in the 90 days after a heart attack increases the risk of death. This is potentially a very important finding.
However, only 137 out of 9,939 patients had been taking statins and then stopped. The fact that the main conclusions of this study are based on results from such a small sample suggests some caution in interpreting these results. The researchers have taken into account some of the factors that may be responsible for this relationship, although they add that they cannot rule out the possibility that there are some other factors involved that were not measured. There are other weaknesses with this study, some of which the researchers discuss:
- As they acknowledge, they were unable to look at the contribution of different types of statins to the outcomes (they only looked at whether people took any type of statin or not, as opposed to individual types of statins).
- They did not have any information on how serious the heart attack was or what treatment was received in hospital.
- It was assumed that if people did or did not take statins in the 90 days after their heart attack, they continued to do this during the entire follow up period (i.e. that if people discontinued statins in that time, they did not start taking them again and vice versa. This may not have been the case for all people.
- The researchers do not look at why statin use may have stopped. The people who stopped taking statins may have been at a higher risk of death for some other reason.
- In recent years, statins have become available over the counter. This study only analyses data from before they were available (2002 and 2004) and the results may be somewhat different if the current general population was studied.
As the researchers suggest, more population-based studies are needed to confirm their findings that statins should be continued after a heart attack given the potential clinical importance. The editorial that accompanies this study suggests that given the small sample size and the observational nature of this data, the study is ‘inherently more hypothesis-generating rather than hypothesis-proving’. Despite this, the editorial’s authors conclude that these findings are important and that ‘continuation of statin therapy following onset of acute coronary syndromes is crucial and is probably most important in patients at high cardiovascular risk’.