Researchers have found evidence that elderly hospital patients treated by female physicians have a lower mortality and readmission risk compared to those treated by male physicians, suggesting that females might be doing something different when treating their patients.

If all doctors could achieve the same level of care as some of their high-performing female colleagues, the team says, there would be 32,000 fewer deaths per year among Medicare patients.

"The difference in mortality rates surprised us," said lead author Yusuke Tsugawa from Harvard University.

"The gender of the physician appears to be particularly significant for the sickest patients. These findings indicate that potential differences in practice patterns between male and female physicians may have important clinical implications."

The team analysed data from over 1.5 million Medicare beneficiaries in the US - 620,000 men and 960,000 women - who were 65 or older and had been hospitalised. They were treated by both male and female doctors - 20,000 female and 60,000 male - between 2011 and 2014.

In this data set, the team also accounted for the reason the patient was hospitalised, as well as the severity of their condition.

They found that those treated by female doctors were 4 percent less likely to die prematurely after their visits and had a 5 percent lower risk of readmission to the hospital in the 30 days following their visit.

To investigate further, the team took the data set and compared their results strictly to hospitalists - healthcare professionals who work inside hospitals and have patients assigned to them based on workflow alone - and found that the results didn't change.

They added this level of randomness to get rid of any chance that female doctors were simply choosing or being assigned healthier individuals who were less likely to suffer a premature death, or had a higher chance of readmission.

The fact that the results didn't change indicates that there might be something that female doctors are doing differently in their treatment of patients, as compared to their male colleagues - although it's not clear what that is as yet.

"There was ample evidence that male and female physicians practice medicine differently. Our findings suggest that those differences matter and are important to patient health," said senior author Ashish Jha.

"We need to understand why female physicians have lower mortality so that all patients can have the best possible outcomes, irrespective of the gender of their physician."

Previous research has found evidence that female physicians generally adhere more to clinical guidelines than male doctors, and are also more likely to provide 'patient-centred communication', but more research is required to see whether these differences translate to saved lives, and what other factors are at play.

"I think it's those practice differences that probably explain the results we have," Jha told Julia Belluz at Vox. "If I'm right on that, it's good news for those of us who are male doctors, because those are things we can learn."

The team's findings are good news to anyone who has a female doctor, but they also highlight the amount of inequality in the US healthcare system.

Female physicians make up only one-third of total US physician workforce - a fact that was highlighted in the study by the ratio of female to male doctors who were involved - and are largely paid and promoted less often than their male colleagues.

The team's work was published in JAMA Internal Medicine.