16 December 2022

Words by Melissa Cunningham, The Age

Women are more likely to die in intensive care from male-dominated conditions, including cardiac issues, than men.

The findings of the world-first study involving almost 1.5 million Australian and New Zealand ICU patients shocked the researchers, who set out to examine how sex and gender may influence a person’s chance of survival.

The most striking difference was following heart surgery, where women were roughly 1.5 times more likely to die in ICU than men. Women are also more likely to die in ICU following a cardiac arrest compared to men.

“The big question we set out to answer was, ‘Does sex or gender matter when you’re critically ill?’ And what we found is that sex absolutely matters,” Austin Health intensivist and lead researcher Dr Lucy Modra said.

“It has an impact on whether you live or die and your illness severity.”

As part of the study, published in the American Journal of Respiratory and Critical Care Medicine, researchers examined more than 10 years’ worth of data from 200 hospitals in Australia and New Zealand.

They found the phenomenon also extended to men. Those who are admitted to ICU for illnesses that are “predominantly female”, such as some metabolic conditions that affect the salt levels in the blood, diabetes complications, or following bone or spinal surgery, were also at heightened risk of death when compared with women.

“We’ve known for some time that women have worse outcomes than men from some typically male conditions, but what we essentially found is that this is a pattern that cuts both ways,” Modra said.

What perplexed researchers most, however, was the “minority effect”, with evidence that the gender balance of patients in an ICU could be linked to survival rates.

“What we found was that women admitted to ICUs with relatively few female patients were more likely to die than men, and vice versa. This was a big surprise – I did not expect to find that at all,” Modra said.

The reasons behind this phenomenon are unclear. Modra speculates it could be linked to cognitive bias.

“It is also possible that clinicians or ICU teams get used to treating either male or female patients … recognising or responding to subtle deterioration for patients in the familiar, majority group,” she said.

The trend of women suffering poor outcomes following heart attacks is not new. Research suggests women who suffer major heart attacks face discrimination from hospitals and receive fewer preventative medications and treatments than men, despite being more likely to die.

This is thought to be in part evidence of an unconscious bias against women, because there is the perception that heart attacks happen mostly to men, possibly leading to complacency from the public and medical professionals.

But Modra suspects there are biological elements at play too. Women who undergo cardiac surgery, such as bypass graft, are often at heightened risk of a poorer outcome.

“Women can actually have blood vessels that are more difficult to graft, for example,” she said. “So there’s technical and biological factors that make it harder to do the surgery.”

Overall, researchers found that men and women generally had an equal chance of survival after being admitted to an ICU in Australia or New Zealand.

However, women were more likely to die if admitted to the ICU for burns injuries than men, in a trend not fully understood but thought to be somehow linked to biological differences when it comes to thermal injuries. There were no differences in mortality in neurological, trauma, musculoskeletal, soft tissue, skin and gastrointestinal diagnoses.

“But yet, when you look at the level of these individual problems, such as cardiac surgery in women, then this really sort of interesting pattern emerges,” Modra said.

“So part of that is trying to untangle whether there’s a possible contribution of cognitive bias or gender bias in some of the things we see in intensive care.”

Dr Stephen Warrillow, the former president of the Australian and New Zealand Intensive Care Society, and a colleague of Modra’s who was not involved in the study, said the findings surprised him.

“It essentially suggests you want your diagnosis to be aligned with your gender, and if it’s not, it might not go so well for you, which is a fascinating finding,” he said.

Researchers are now calling for ‘minority effect’ to be recognised in studies, education and clinical reasoning – a move backed by Warrillow.

“The thing for me, as an intensivist, that makes me wonder if much of it is underlying biological considerations and how much of it is our approach to care or the subconscious bias of clinicians when they’re assessing someone,” Warrillow said. “The answer is, we don’t know yet. But we sure need to find out.”