A press release from the University of Pennsylvania demands your attention: “In the U.S., COVID-19 wasn’t sole cause of excess deaths in 2020.”
The first sentence reads, “By the year 2017, the United States was already suffering more excess deaths and more life years lost each year than those associated with the COVID-19 pandemic in 2020.”
Immediately, you think, “what does this mean? Are we overestimating COVID-19 deaths?”
Spoiler alert: the press release does not accurately translate what the researchers found. This is dangerous and irresponsible, and it comes directly from the lead author’s university press office. This is not a case of a reporter misinterpreting results or aiming for click-bait.
Let’s discuss what the term “excess deaths” means, what the research results actually tell us, where the press release went wrong, and why we should care.
What Are Excess Deaths? How Do We Calculate Them?
You have probably heard the term “excess deaths” in the last year. Calculating excess deaths can give us a quick shortcut to a rough estimate of how many people have died due to a major event such as an environmental disaster (e.g., Hurricane Maria in Puerto Rico) or a pandemic (e.g., COVID-19).
Simply put, excess deaths represent the actual number of observed deaths in the population minus the expected number of deaths over a period of time. We can estimate the expected number of deaths in a population based on prior data. This is actually easier than it seems because it would take a pandemic, war, famine, considerable policy shifts, or some other major catastrophic event to significantly move the needle on the number of deaths among a population of 328 million people. Thus, when something does cause the needle to move, we can calculate a rough estimate of how much the needle moved and attribute the cause.
Here is a simple exercise. In the U.S., about 2.85 million people died in 2019. Among those deaths, about 659,000 were due to heart disease and 599,000 were due to cancer. Combined, those two causes of death represent about 44% of all deaths in 2019. Those numbers should not change significantly from year to year without a major…