Covid-19 is still driving Australia's above-average mortality rate, research showed on Monday, with experts predicting the disease's impact will continue to be felt for years to come.

The Australian Actuaries Institute found that five percent more people died than would be expected in 2023, amounting to 8,400 excess deaths.

Experts measured the number of people who had died as a direct or indirect result of Covid and found the excess mortality rate was still higher than pre-pandemic levels.

About 4,600 deaths were directly attributed to Covid-19, the ninth leading cause of death last year.

Non-Covid-19 excess deaths, meanwhile, were "particularly apparent" in Australians over 75 years old -- with previous infections and interruptions in healthcare related to Covid increasing risks related to heart disease, stroke, diabetes and dementia.

Delays in routine or emergency care and undiagnosed Covid-19 were cited as possible reasons for the higher-than-usual death rate.

Still, the excess mortality rate was lower in 2023 than it was in 2022, according to experts.

"It's encouraging that each successive Covid-19 wave has, so far, resulted in fewer deaths than the previous one," Actuary Institute spokeswoman Karen Cutter said.

"However, we think that Covid-19 is likely to cause some excess mortality for several years to come, either as a direct cause of death or a contributing factor to other causes such as heart disease."

She added the "new normal" level of mortality was likely higher than it would be had the pandemic not occurred.

The report also found Australia's excess mortality was lower than the global average -- with Ecuador, Mexico and Russia showing the highest rates of unexplained deaths.

New Zealand had the lowest excess mortality rate of the 40 countries for which data was available.