July 2, 2020
Hello friend! Welcome to Scrap Facts.
I'm a reporter covering health and science with insatiable curiosity. I love everything I learn, not all of which gets its own story. Each week, I'll bring you some of my favorite facts that I picked up on the job or while out living life.
How do you measure the impact of a pandemic?
All of the numbers floating around in epidemiology these days—fatalities, case counts, percent of positive tests—have their own strengths and weaknesses. Alone, they can give snapshots of the pandemic, but you need several of them get the full story.
Next Thursday, July 9, at 11 am US eastern, I'll be interviewing Brooke Nichols, a public health economist and assistant professor at Boston University’s School of Public Health live (virtually) for Quartz. I’ll be asking her to break down some of these metrics, and also to explain which ones to follow as treatments and vaccines for Covid-19 progress.
Charging for an event? In this economy? No way—it’s F R E E! All you have to do is register here!
And here’s a teaser fact to whet your appetite for health stats:
In one metric used in public health economics, life expectancy is based on the longest living people on the planet—which now happen to be women in South Korea.
Found while reporting: How do you measure a Covid-19 fatality?
There’s a metric in public health called years of life lost, or YLL. It’s a way of looking at fatalities due to a given condition and factoring in when someone died. If someone was expected to live to 75, but died at 65 due to cancer, their YLL to cancer would be 10 (1 person x 10 years early = 10 YLL). Now the pandemic’s gone on for a bit, scientists have used YLL to publishing estimates saying that those who get sick with Covid-19 are losing over a decade of life on average.
YLL weighs young deaths more than older deaths. There may be a good reason you’d want to do that—like convincing non-health experts to fund a campaign to decrease diarrheal disease, which tends to affect and kill more children. That said, it can have some uncomfortable consequences when acted on at a state or national level (I’m looking at you, Arizona Department of Health).
But anyway, it presents an interesting issue: How do we know how many years of life were actually lost?
YLLs have been around for nearly a century, but they didn’t get off the ground in the public health world until the the 1990s, when researchers at the World Health Organization and the Institute for Health Metrics and Evaluation at the University of Washington published the first Global Burden of Disease study (it comes out every couple of years). This group estimated how long all people should live by looking at the longest some groups of people were living at the time.
From my article:
When researchers the first published the Global Burden of Disease report in 1993, they used women from Japan (pdf p. 5), with an average life expectancy of 82.5 years, as their baseline; for men, they assumed 80 years. In recent years, the WHO has switched to nearly 92 years for all genders, based on the predicted life expectancy for women living in South Korea in 2050.
But wait! Life expectancies differ drastically across countries—so it’d be better to use each country’s life expectancy, right? Wrong—it’s still complicated:
In the United States, the average life expectancy is 78.6 years for someone born in 2016. But even that doesn’t cover all the variation; systemic racism has reduced the average life expectancy for Black Americans born in 2015 to around 75, compared to 79 for white Americans.
So YLL can still exclude demographics within certain countries and undercount their pain.
YLL is one reasons many public health officials didn’t take the Covid-19 pandemic seriously at first; it looked like it was only affecting older adults, so it didn’t have a very high YLL. But now, we know better—younger people can become critically ill.
YLL isn’t necessarily a bad metric; it just has its shortcomings, which can have dire consequences if they’re ignored. But here in the US, we need to use all means necessary to convince public health authorities to take the pandemic seriously. Hopefully, reports showing that Covid-19 is having a substantial toll on YLLs can help that cause.
That’s all for now—stay curious, friend ❤️
Top image by E. Y. Smith, headshot drawing by Richard Howard.