Scientists identify China’s mysteriously massive cancer burden

Tai Chi in the park
Tai Chi in the park
Tai Chi in the park
Flickr, PTorrodellas

Scientists in Seattle, Australia and China report in The Lancet today on the leading causes of death and disability – as well as the many positive health trends – in a rapidly modernizing China.

Perhaps unsurprisingly, the study, based on Global Burden of Disease data compiled at the University of Washington’s Institute for Health Metrics and Evaluation (IHME), found that China’s rapid economic development over the past few decades has been accompanied by a decline in ‘diseases of poverty’ like malaria, vaccine-preventable infectious diseases and child malnutrition.

The world’s largest nation and new emerging superpower also has seen remarkable progress at lowering childhood and maternal mortality, along with an equally unsurprising rise in the burden of diseases and disorders familiar to wealthier countries such as heart disease, stroke and dementia. Air pollution gets special attention as well.

NPR reported As China Gets Richer, First World Diseases Take Hold, which was the primary theme of the The Lancet special report on China. Similarly, Forbes reported that China’s health problems mirror wealthy nations.

Not quite.

One surprising – and not completely understood or explained – finding out of the study is that China appears to be the undisputed world leader for certain cancers: Liver, stomach and esophageal.

I asked a policy translation specialist at IHME, Katie Leach-Kemon, to dig into this a little deeper using one of IHME’s data visualization tools known as a ’cause pattern’ analysis. Leach-Kemon compiled this graphic below showing age-standardized rates of years-of-life-lost due to different cancers around the world. Here’s a link to the active chart online. Notice my red highlights:

This is not an artifact of China’s massive population. This comparison of cancer rates, including both poor and wealthy countries, is standardized to adjust for population size, age and demographics.

What this shows, Leach-Kemon explained, is that compared to most other countries China appears to have especially high rates of liver, stomach and esophageal cancer. China also has a high rate of lung cancer, the chart shows, which is likely due to the high rate of tobacco smoking and probably air pollution. Researchers at IHME say more than half the high rate of liver cancer mortality is due to hepatitis B infection (which can be prevented by a vaccine).

But the Seattle scientists were less able to explain the exceptionally high rates of cancer of the stomach and esophagus.

They suggested this could be due to eating lots of smoked foods and salt, or not enough fruit, drinking too much alcohol – or maybe smoking. Meaning, they aren’t sure. For an even more dramatic depiction of how bad these cancers are in China, take a look at this ’cause pattern’ analysis Leach-Kemon did (at my request) comparing China’s cancer rates only to the wealthier countries:

China Cancer GBD
IHME

It’s often difficult to establish cause-and-effect with health problems. It may never be possible for scientists to sort out the exact proportion of lung cancer cases caused by smoking from those cases caused by air pollution, for example. But it doesn’t take a rocket scientist to conclude that air pollution, like smoking, is bad for you.

China, while it is rapidly making economic progress, suffers from immense environmental problems. Air pollution is just the most notable one. Many of China’s rivers are so polluted they have no fish. A recent CNN story of China’s ‘cancer villages’  indicates officials are beginning to recognize there is a serious cost to mimicking the West’s reckless approach to industrialization in which we treated the environment like a waste dump for our factories.

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Nobody seems to know what this particular finding means yet, but what’s interesting is that the data is there for anyone in the world to analyze and explore.

When the Seattle gang of global health number-crunchers at IHME set out to do this massive, new Global Burden of Disease study (evaluating 650 million or so health data sets from nearly 200 countries), one of their primary goals was to make their findings publicly accessible. Halfway through this ambitious project, they realized the data could not be understood (even by the experts) unless it could be handled as ‘visual information.’

Anyone, even a journalist (in my case, with help from smart folks like Leach-Kemon) can explore the world of global health, death and disability using IHME’s online data visualization tools. The experts at the Institute actually encourage it, and would like your feedback through social media like Twitter and Facebook.

Data alone can’t answer everything. It may just raise a new question. But what is most potentially transformative about this report on health trends in China is not so much the findings as the way they are being reported. Anyone can now dig in as deep as they want, asking their own questions and maybe even coming up with their own answers.

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