Do women fare worse than men after a heart attack?

The Mail Online has reported that, "Women are three times more likely to die after a heart attack than men", while BBC News said that, "Fewer women would die if given the same treatment as men".

Despite these rather alarming headlines, the study the news is based on reviewed people hospitalised for a heart attack in Sweden, not the UK.

When looking at the raw data, there were no differences in the number of deaths between men and women who'd had a heart attack.

But when researchers took into account that women tend to live longer than men in the developed world, there was an unusually high death rate in female heart attack patients.

Interestingly, when researchers only looked at patients who'd received "best-practice" treatment, this removed any differences between men and women.

This may suggest women may have been less likely than men to receive guideline-indicated treatments in Sweden – but this can't be stated as fact, as the study didn't look into this further.

This study raises more questions than it answers, and we can't assume the data has any relevance to women in the UK.

Where did the story come from?

The study was carried out by researchers from the University of Leeds and the University of Leicester in the UK, and the Karolinska Institutet and Uppsala University in Sweden.

Funding was provided by the Swedish Heart and Lung Foundation, with one researcher additionally funded by the British Heart Foundation.

The study was published in the peer-reviewed Journal of the American Heart Association.

There's a great deal of speculation in the UK media about why the study found the results it did.

But much of the reporting – especially the headlines – failed to make clear that this study was based on Swedish data.

The Sun went as far as saying that, "Women are dying from heart conditions 'because the NHS cares for men better'."

Until similar research is carried out in the UK, we won't know whether this is actually the case.

What kind of research was this?

This was a cohort study of people who received hospital care for heart attack in Sweden between 2003 and 2013.

The researchers looked at the care they received and gender differences in treatments and survival after a heart attack.

Such a study is useful for looking at trends, but can't necessarily explain the reasons for any differences observed.

What did the research involve?

The study included all 73 hospitals in Sweden that provided care for people who'd had a heart attack between January 2003 and December 2013.

A total of 180,368 adults were hospitalised for heart attack over this 10-year period.

The researchers collected patient data from a Swedish dataset known as SWEDEHEART, a registry of patients being cared for after a heart attack. The registry is thought to contain 96% of relevant health records.

Researchers looked at relative survival at 1 and 5 years after hospitalisation for a heart attack.

"Relative survival" compares what's expected in the general population based on age, gender and year, taking account of the fact women are more likely to live longer than men.

What were the basic results?

Women who'd had a heart attack tended to be older than men who'd had one, and were also more likely to have other illnesses like diabetes, high blood pressure and heart failure, but were less likely to be smokers.

There were more deaths among women who'd had a heart attack than men (46% versus 35%), and average time to death was also shorter (1.7 versus 1.9 years).

Despite this, women actually had a slightly reduced risk of death from any cause at 6 months, 1 year and 5 years compared with men (varying from a 6% to 12% relative risk reduction).

But women fared worse than men when compared with what would be expected for survival rates in the general population.

For women suffering the "classic" heart attack (where there are typical features on the ECG, called ST-elevation myocardial infarction, or STEMI), 83% of women survived to 1 year and 75% to 5 years, compared with 87% and 82% respectively for men.

This related to about a triple risk of death at 1 year and a doubled risk at 5 years for women.

Women who'd had heart attack symptoms without the classic ECG features (non-STEMI) had lower survival only compared with men at 5 years (73% versus 76%).

The interesting point was that adjusting the analyses for age and other illnesses made little difference.

But adjusting for the use of guideline-indicated treatment essentially removed the differences in deaths between men and women – in other words, women treated in line with best-practice guidelines had the same survival rates as men.

How did the researchers interpret the results?

The researchers concluded: "Women with acute myocardial infarction did not have statistically different all-cause mortality, but had higher excess mortality compared with men that was attenuated after adjustment for the use of guideline-indicated treatments."

They said: "This suggests that improved adherence to guideline recommendations for the treatment of acute myocardial infarction may reduce premature cardiovascular death among women."

Conclusion

This study is based on a large quantity of reliable registry data over a 10-year period in Sweden. It raises some concerning points.

The death rate following a heart attack is higher among women than men, when allowing for the fact that women in general should live for longer than men.

When researchers only looked at patients who received best-practice treatment, there was no difference in survival between men and women. This is worrying, as it suggests that women were less likely to receive best practice treatment.

But this can't be assumed or examined in more detail at this stage. The study only looked at raw facts and figures, and isn't able to look into the reasons behind individual treatment decisions.

In particular, the researchers only looked at treatments given at hospital discharge, so they're not able to review and compare care received while in hospital.

And when looking at population survival data, we can't be certain that factors like the socioeconomic mix is the same in the UK and that all relevant confounders were taken into account.

We should be careful before concluding that women who've had a heart attack receive poorer care than men, especially when looking at NHS care – a fact the UK media should have highlighted.