Researchers accepted that reporting delays could be a contributing factor, but said shortfalls in clinical staffing, capacity, and experience at weekends were also likely to play a role.

Overall, the average number of global deaths from coronavirus were six per cent higher on weekends compared to weekdays - 8,532 compared to 8,083 - throughout the pandemic, researchers said.

Experts from the University of Toronto in Canada analysed all deaths reported to the World Health Organisation COVID-19 database between March 7, 2020 and March 7, 2022.

The findings, which are due to be presented at this year's European Congress of Clinical Microbiology and Infectious Diseases (ECCMID) in Portugal later this month, suggest the US had on average 1483 weekend deaths compared to 1220 on weekdays - a 22 per cent increase.

Brazil had an average of 1061 weekend deaths compared to 823 on weekdays, which is a 29 per cent increase, and the UK had on average 239 weekend deaths compared to 215 on weekdays - an 11 per cent increase.

Further study looking at the average number of COVID deaths on individual days of the week found the increase was particularly big when comparing Sunday to Monday - 8850 compared to 7219 deaths - and Friday to Monday - 9086 compared to 7219.

One of the researchers, Dr Fizza Manzoor, said delays in reporting deaths on weekends do not account completely for differences in different countries - with Germany reporting fewer average deaths at weekends (137) compared to weekdays (187).

"Bureaucratic delays on weekends alone do not explain why there are fewer documented COVID-19 deaths on Mondays compared to Fridays, and reporting lags alone cannot explain why the increase in weekend deaths was so substantial in the USA and not seen in Germany." Manzoor said.

"Instead, the 'weekend effect' is also likely to be due to shortfalls in clinical staffing, capacity, and experience. What's more, our findings suggest that this problem is not resolving despite improved health system performance and awareness over the course of the pandemic.

"There is an opportunity for health systems to further improve clinical care on all days of the week."

The researchers accepted the conclusions of the study, which has been peer reviewed, could be limited by false negative results, missed cases, and data entry errors, and that the available data does not account for disease severity or explore the impact of local policies and public health interventions in individual countries.

Australian Associated Press