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If 7 billion people are living on Earth, how many are dying?

This is a skull
Flickr, aldinegirl87

One of the big news items this week was that the global human population was expected to reach 7 billion with a baby born on Halloween, according to a gang of UN statisticians.

That was yesterday. Today is Day of the Dead, or Día de los Muertos in Mexico.

So let’s talk about dying.

No, this is not a Malthusian strategy for popluation control. What we will examine is  how death actually causes population growth — and how little we know about why people die.

This will lead us into a discussion about a technique known as “verbal autopsies,” which some Seattle scientists are working to refine, and a new phone app that could help reduce the global birth/death burden on the planet.

It is truly a killer app.

First, it needs to be said that we can’t really know when the global population will have precisely crossed the 7 billion person threshold. In fact, as the BBC notes, we may be off by many months — or even years — in either direction with this estimate.

Secondly, we are equally in the dark about how and why people die, about 50 million per year. Most countries around the world have very poor mortality statistics.

But one thing we do know for certain is that those countries with the highest mortality rates are also the countries with highest population growth.

Huh? Yes, you read that right.

How can high rates of death lead to higher birth rates?

Well, it makes sense if you give it a little bit of thought. Go ahead, give a little.

One reason for this apparent contradiction is that most parents in poor countries depend on their children as both labor on the farm (most of the world’s poorest are farmers) and for support in their old age or in the case of illness. Children are the poor world’s social security system.

Many of the hand-wringers on population growth say what we need is to get more birth control and family planning out to these poor folks. We do, but that doesn’t eliminate the economic incentives of these poor families to have more kids. If parents know half of their kids may die of diseases of poverty and they figure they need five for the farm, they have ten kids. Simple math.

Birth rates go down as income goes up

Conversely, as you reduce poverty in a community over time, the birth rate declines. This link between poverty rates and birth rates is well-documented and is known as the demographic-economic paradox.

Don’t feel so bad if it’s all a bit confusing. That’s why they call it a paradox.

Poverty and poor health, hand in hand.

Next, consider that people, including children, don’t just drop dead from disease. Illness takes time and an economic toll. As a poor family deals with a sick child, the mother is not available to help with the farming. The family’s income declines. Poverty and disease are the most common of vicious cycles.

What this means is that improving health and reducing mortality can work to reduce poverty which eventually causes birth rates to go down. Voila!

It’s not always that simple, of course, and doesn’t happen overnight. Reducing poverty also tends to improve health — so plenty of folks fight the chicken-and-egg debate over which one is primary when it comes to what may be most driving the improvements in the demographic-economic paradox.

But the main point here is that health, poverty, death and population growth are linked in a feedback system — and that reducing child mortality may be, could be, one of the most effective ways of reducing population growth. (If you don’t believe me, see the post below this one or go watch this great TED video making that case from the world’s most entertaining statistician, Hans Rosling.)


So what’s this have to do with scientists working on phone apps for “verbal autopsies?”

“We’re not talking to dead people, no,” said Alan Lopez, with the University of Washington’s Institute for Health Metrics and Evaluation as well as the University of Queensland in Australia.

Lopez and his colleagues, including Chris Murray, director of the UW health metrics bunch, specialize in analyzing global health data. Murray and Lopez are actually world-renowned, if not always embraced, for being some of the most influential global health number-crunchers (health geeks) around.

And one of the things that has long bothered many experts on global health is how little we know about what kills people.

“Worldwide, about 50 million people or so die every year,” said Lopez. Most of them, 40 million or so, are in developing countries which have poor or no records on cause of death.

Few of those who die in poor countries are seen by anyone with even rudimentary forensic skills, let alone trained physicians. And even those who are seen by physicians are often misdiagnosed, Lopez said, either because the physician doesn’t care (the patient is dead after all) or doesn’t have the time to do a proper cause-of-death.

Meanwhile, the global health community needs to set priorities for fighting diseases based on their best estimates of which diseases create the biggest burden. Many of the big killers — malaria, pneumonia, malnutrition, to name a few — kill mostly kids.

“The lack of reliable information about cause of death worldwide is a big problem,” said Lopez.

To put it bluntly, it’s hard to know if you’re winning the battle if you can’t identify the enemy. And he said there’s little chance of immediately expanding the number of health workers out there just to improve mortality statistics.

But there has been this technique known as the ‘verbal autopsy’ — a standardized set of questions that even low-skilled workers can ask family members regarding symptoms, medical history and other facts regarding the recently deceased.

“The problem is that there’s been a tremendous lack of confidence in the reliability of verbal autopsies,” said Lopez. So Murray, Lopez and the number crunchers at the UW Institute — primarily led by Rafael Lozano — began to examine data.

“What was most exciting about this project is that we showed the validity of the approach,” said Abraham Flaxman, a mathematician who came to IHME from Microsoft Research in 2008. Many experts were suspect of verbal autopsies but, as Flaxman said, most doubts were based not on evidence of problems but from lack of any evidence either way.

The UW number crunchers dug in, did tests in six countries and recently issued this extensive report describing their proof of the value of properly done verbal autopsies. It’s a bit thick, but feel free to read it yourself.

What’s equally potentially transformative here is that Flaxman, working with UW computer scientist Gaetano Boriello, converted the old pen-and-paper verbal autopsy into a digitized format that can be used on a smart phone.

“We’re almost ready for prime-time (with the app),” Flaxman said. “My hope is that verbal autopsies can get done fast and cheap.”

Then we’ll really know what’s killing people, mostly children, worldwide and perhaps greatly reduce childhood mortality — thus reducing the rate of global population growth.

Happy Day of the Dead!



About Author

Tom Paulson

Tom Paulson is founder and lead journalist at Humanosphere. Prior to operating this online news site, he reported on science,  medicine, health policy, aid and development for the Seattle Post-Intelligencer. Contact him at tom[at] or follow him on Twitter @tompaulson.