Cause-of-death study shows progress – albeit unequal– and big red flags

The overall trend from the Global Burden of Disease 2013 analysis is good news, but that's not the whole story.

The overall trend from the Global Burden of Disease 2013 analysis is good news, but that’s not the whole story.

A massive cause-of-death study finds that we are living about six years longer than we did in 1990, that child deaths have plummeted thanks to greatly expanded immunizations, among other things, and that non-communicable diseases like diabetes are gaining prominence as top killers largely because of big gains made against infectious diseases.

That’s the mostly good, and perhaps not-so-surprising, news from the latest Global Burden of Disease study, an analysis issued regularly by the University of Washington’s Institute for Health Metrics and Evaluation (because things change) that was published this week in The Lancet. The scientific report in the journal has a ridiculously long title that hints at just how difficult and complex it really is to try to pin down the leading causes of death worldwide. You can also read about it, and explore the data online, at the UW Institute’s website.

Chris Murray

Chris Murray

“Life expectancy went up almost everywhere, with the notable exception of southern Africa (due to HIV-AIDS),” said Chris Murray, lead co-author and director of the Seattle-based global health number-crunching institute.

In low-income countries, Murray said, the big gains over the study period 1990-2013 were made mostly by reducing child deaths from diarrhea (largely those caused by rotavirus) and pneumonia. In higher-income countries, he said the gains have come from reducing deaths from ischemic heart disease.

GDB2013: Changes in life expectancy by region and cause, 1990-2013. The Lancet

GDB2013: Changes in life expectancy by region and cause, 1990-2013. (The Lancet)

The bad news in the Global Burden of Disease 2013 report, according to Murray, comes from a deeper dig into the mortality trends. This is the first time the massive analysis, which involved more than 700 researchers working on reams of death data of varying quality and content type from 188 countries, published findings broken out country-by-country.

What emerged is that the welcome overall increase in life expectancy and decline in some major infectious disease killers over the past two decades or so serves to mask another trend that might be dubbed “global health inequality” –  as well as some neglected increases in certain killers, like a still-poorly understood surge in deaths from chronic kidney disease.

“The increase in chronic kidney disease, which runs counter to the overall trend, should be a big red flag,” Murray said.

This epidemic of kidney disease has received some attention in Central America, where the problem has been blamed on pesticide exposure or perhaps a yet-unidentified virus, but he said the report revealed it is also popping up in China and other parts of the world as well. “This appears to be a global phenomenon.”

Beyond looking at isolated causes of death, the study also examined whether we are making much progress with the global health goal some have dubbed the “Grand Convergence.”

As Humanosphere reported earlier this year, the idea here is that an equity approach to fighting disease should end up with little difference in causes-of-death between the rich and poor. That is, the causes and rates of death should be the same for all regardless of income or wealth.

We’re not there yet, by a long shot, but many experts like Dean Jamison and Harvard University’s Larry Summers contended in their Global Health 2035 report, unveiled at the last World Economic Forum meeting in Davos, that we could get there in a few decades with the right investments and global health strategies – and that such a healing “convergence” would, in addition to improving health equity, create a tremendous economic benefit worldwide.

That would be great, but Murray and his colleagues found little evidence to indicate we are moving closer to convergence or global health equity.

“What we want to see is not that these causes of death are declining at the same rate for everyone overall,” Murray said. Convergence, he said, will require that those mostly poor countries see a much greater and faster decline in many causes of death than in the richer countries.  What Global Burden of Disease 2013 showed, he said, is actually a widening gap for many leading causes of death like heart disease, diabetes and even road injuries.

“This is telling us that rather than seeing convergence, in many cases we are actually diverging,” Murray said.

Other interesting bits and pieces contained within the report include a somewhat muted critique of how poorly India is collecting cause-of-death data; that death from drug abuse (separate from alcohol abuse, which is also still a big killer) disproportionately afflicts the U.S., Australia and Norway among rich countries; that death rates from most cancers are going down but not for pancreatic, kidney and liver cancers; and that doctors have inadvertently messed up the stats on Alzheimer’s disease.

“There’s been a big change in physician coding practices that makes it much more likely for them to attribute Alzheimer’s as a cause of death,” Murray said. Many have seen the studies and news reports claiming we are experiencing a big surge of dementia and Alzheimer’s, he said, which is partly true in raw numbers because of aging populations. But the claims of 300 or 400 percent rate increases in Alzheimer’s in the U.S. and Europe is mostly an artifact of this change in physician behavior over the past few decades.

“In short, there is no tsunami of Alzheimer’s out there,” Murray contends. The study compared the death codes against disease prevalence studies and what they found was “no change or even a slight decline” in the rate of dementia overall. This could be due to progress made against heart disease, he said, which also could explain a reduction in so-called vascular dementia (dementia caused by reduced blood flow to the brain).

“Always a few surprises,” said Murray. The purpose of the study and the death data, he added, is to inform our strategies going forward as the international community debates the next set of global health and development goals – the so-called post-2015 development agenda.

Country specifics need to be taken into account when setting the overall global goals, Murray said, and the Global Burden of Disease will also allow nations to learn from one another by identifying best practices and areas in need of special attention.

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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]humanosphere.org or follow him on Twitter @tompaulson.