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An analysis of mortality statistics suggests the death count in the United States from COVID-19 is higher than the 1.1 million officially linked to the disease, according to new University of Minnesota research.

A U sociologist teamed up with public health researchers in Boston and Philadelphia to analyze excess deaths — mortality from natural causes that surpasses historical norms. They found a pattern that only makes sense if COVID played a key role. Excess deaths not ascribed to COVID almost always occurred at the beginning of pandemic waves, and then disappeared when those waves reached peak levels of illness, the researchers found.

"If these excess natural cause deaths had nothing to do with COVID, you would probably see them happening throughout this period, irrespective of when the COVID waves are," said Elizabeth Wrigley-Field, the U sociologist and demographer who coauthored the study.

The results were published in a prestigious science journal, the Proceedings of the National Academy of Sciences, and argue that many of the 162,000 excess deaths assigned to other causes during the first 30 months of the pandemic should actually be tied to COVID. Exactly how many isn't specified.

The accuracy of COVID death reporting remains divisive, even after the federal COVID public health emergency ended last spring. Donald Trump as president in 2020 had questioned whether doctors were inflating COVID death counts to obtain more federal relief money. Some lawmakers in Minnesota early in the pandemic questioned whether the state's death toll was inflated by as much as 40%.

The latest findings come amid a decline in COVID activity, following an increase in illnesses driven by holiday gatherings and the fast-spreading JN.1 coronavirus variant that made up 78% of infections at the end of 2023. Testing in wastewater treatment plants is showing the lowest viral levels in Minnesota since Thanksgiving.

The most likely explanation for non-COVID deaths surging right before pandemic waves is that people weren't worrying about COVID as much or testing for it at those times. So deaths related to the infectious disease were missed, the study concluded. Testing then rapidly increased as the pandemic waves became apparent, which reduced the share of excess deaths attributed to other causes.

Minnesota's official count was updated Thursday to 15,776 COVID-19 deaths, including 220 deaths in 2024 that were mostly among people 75 and older.

The latest research suggests that Minnesota's total is close to the mark; throughout COVID waves, far fewer of the state's excess deaths were attributed to causes other than the infectious disease. Federal estimates show that COVID caused almost 4,000 more deaths than expected in the winter 2020 pandemic wave in Minnesota, for example, compared to 150 more deaths than expected from other causes.

The Minnesota Department of Health for the first three years of the pandemic had workers verify that deaths linked to COVID on death certificates were actually caused by the infectious disease. The state halted that costly process at the start of 2023 and started counting all deaths as related to COVID when people had tested positive for the infectious disease and their death certificates listed it as a cause, said Lydia Fess, an epidemiologist in the Health Department's emerging infectious diseases section.

Internal research showed little change with this switch, and that COVID death reporting remained consistent across age, race and other demographic categories, she said.

Other factors beyond underreporting of COVID could have resulted in more excess deaths from non-COVID causes during pandemic waves. Minnesota hospital leaders warned during the pandemic that overcrowding threatened to delay or worsen care and increased risks of harm for all patients. However, the authors of the latest study noted that excess deaths from non-COVID causes tended to decline at the peak of pandemics, when the consequences of hospital overcrowding should have been at their worst.

The authors called for more consistency in the U.S. system of reporting deaths, because excess deaths from non-COVID causes appeared inflated in some rural counties and regions of the country where political appointees and others lacking medical training were responsible for declaring official causes. Those officials may have allowed political views about COVID and the nation's pandemic response to influence their determinations, or have been persuaded by family members who didn't want COVID listed on death certificates, they wrote.

Northeastern states such as Massachusetts and Rhode Island attributed so many of their excess deaths during the pandemic to COVID that it raises the potential of an overcount. However, Wrigley-Field said those states probably had fewer deaths from non-COVID causes, because their aggressive responses to the pandemic reduced the threat of other infections such as influenza.