A massive study of death, disability and disease on Earth, coordinated out of Seattle and to be officially published in The Lancet on Friday, could do for global health something like what Galileo did for the solar system.
It’s called the Global Burden of Disease (technically, the Global Burden of Disease, Injuries and Risk Factors Study 2010) and it is, like its earlier incarnations dating back to 1990, almost guaranteed to provoke and disrupt the international community’s approach to improving global health.
The good news is that people, in general, are living longer. The bad news is more of them seem to be fatter, still smoking too much and suffering from disabilities.
Just as the 16th century astronomer Galileo – much to the dismay of the religious orthodoxy of the time – displaced Earth from its celestial prominence in favor of the Sun, the new Global Burden of Disease may displace infectious disease from its position as the categorical center of the global health universe.
Think the top three killers in the world are scourges like AIDS, tuberculosis and malaria? Think again, of heart disease, respiratory infections and stroke.
Think preventing death is the best way to tell if we’re winning the war on disease? You better think again about that as well since rates of obesity, chronic pain, injury and mental illness may say more….
“We were surprised by many of the findings,” said Chris Murray, one of the founders of the study and director of the Institute for Health Metrics and Evaluation (IHME) at the University of Washington.
“The simple purpose of this study has always been to provide the best scientific evidence on patterns of disease and disability to help us make sense of what’s happening out there and set priorities,” Murray said.
Sounds simple enough. So why did it take some 500 researchers more than five years to do it?
To begin with, this third version of the Global Burden of Disease (let’s call it the GBD) has greatly expanded the number of diseases, disorders and injuries it has evaluated to nearly 300. Health diagnoses and death data, especially in poor countries, are highly variable and full of gaps. Experts often don’t agree on what to measure, or how.
“When Chris and I started on this (for the first GBD, in 1990), the emphasis in international health was largely on mortality,” said Alan Lopez, Murray’s long-time partner in global health number-crunching and head of population health at the University of Queensland in Australia.
When the two factored in disability as well as deaths, Lopez said, one of the most surprising results was to discover one of the largest contributors to global disability (and death) is mental illness. That remains true today, he said, yet mental health is perhaps one of the most neglected of neglected diseases in global health.
So will this new, much more comprehensive GBD really shift the global landscape? Will the fact that this study is the largest systematic effort ever made to quantify the world’s health status and trends, featuring something like 650 million health estimates, create a more scientifically based global health agenda?
One measure of impact might be the level of pushback.
“This will set, or more accurately re-set, the agenda for the priorities and the politics of international health,” said Richard Horton, editor at The Lancet and a board member at IHME. “Many won’t like that … which is why there have been a lot of skirmishes over this study already, even before the findings have been reported.”
One of those skirmishes erupted earlier this year when Murray and his colleagues reported, in an early release of some GBD data, that the total death toll and the conventional wisdom on malaria’s victims was wrong — the latter being the belief that it kills kids mostly, not adults.
The Seattle researchers found that the World Health Organization, holder of the conventional wisdom, had seriously underestimated the malaria death toll (by about half) and that at least 30 percent of those killed by the parasite were adults or teens. The WHO strongly challenged the Seattle number crunchers and criticized their findings as flawed. For some, the debate continues.
That kind of thing happens a lot to Murray and his metrics gang.
Take, for example, when they said in 2010 that maternal mortality was significantly lower than the standard estimates. The WHO slammed this report as well, at first, then eventually quietly ‘revised‘ its numbers in agreement. Some women’s health advocates sought to have the Seattle team’s data suppressed, fearful such a major reduction in maternal death numbers would undermine a fund-raising campaign aimed at improving reproductive health worldwide.
Horton predicts the new GBD will similarly provoke organizations like WHO or others with vested interests in specific health causes to cry foul, for the same self-serving reasons.
“I hope not, but I won’t be surprised,” he said. “These data are very powerful, with immense policy implications that may directly gore someone’s favored ox. It happens all the time in global health. Changing the agenda means somebody may lose funding and support.”
The GBD 2010 study, which was funded by the Bill & Melinda Gates Foundation, finds that heart disease, stroke and respiratory diseases are among the world’s leaders when it comes to disease burden. These are followed by diarrhea (fourth) and low back pain (sixth). HIV-AIDS and malaria ranked fifth and seventh place, respectively, closely followed by many other chronic, non-communicable diseases or disorders.
(Below is one of many graphs in the GBD, this one showing Years of Life Lost – YLLs – by cause over time)
“Heart disease went from fourth to first, when comparing 1990 to 2010,” Murray said. HIV-AIDS has increased greatly as an overall cause of death, he noted, but still ranks below the primary non-communcable, chronic lead killers.
The study didn’t just focus on death and, in fact, tries to correlate and compare disability with mortality using a number of statistical measures such as the original brainchild of Murray and Lopez known as the DALY, or ‘disability adjusted life year.’ The idea, put simply, is to estimate the number of life-years lost due to disability to provide global health metricians with a comprehensive unit of assessment.
The new GBD goes way beyond the DALY, however, using a number of innovative statistical tools, self-correcting algorithms and a computerized database that will allow researchers to search the data interactively using a visual information platform. It’s too much to try to describe here, so stay tuned for my story tomorrow explaining what Burger King and Netflix have to do with all this.
The traditional global health focus on simply preventing death, mostly by preventing infectious diseases such as HIV-AIDS, TB and malaria or acute threats like hunger and death in childbirth, has been fairly successful over the past two decades — a success story that, in one sense, has led to an increasing proportion of disability and suffering caused by problems like obesity, diabetes, chronic pain and mental illness. This requires a new mindset, and a new way of looking at global health, Murray said.
“We’re not trying to set policy, but we are trying to get policymakers to base their decisions on the best possible data,” he said. “And the data show that the global health landscape has changed.”
And when it comes to infectious disease it can change back quickly, responded King Holmes, head of global health at the University of Washington and a world-renowned expert on HIV and infectious disease. Murray gave a sneak preview of the GBD results to select members of the UW last week, offering it up for praise and critique.
“I remember people telling me when I was young not to go into infectious disease because we’d gotten most of them under control, there was no future in it,” Holmes said. “Then, in 1981, we saw AIDS. I would like to suggest it’s probably premature to write the obituary of infectious diseases just yet.”
Further, he said, many diseases like cancer that are categorized as non-communicable diseases are known to be caused by infectious agents and many more probably that we don’t yet know about.
He added that another factor to consider is the ability to effectively intervene, either by treatment or prevention, as opposed to simply setting priorities based on overall burden. Fighting many infectious diseases, Holmes said, offers a big bang for not so many bucks while other problems may have costly or complex interventions infeasible for poor countries.
UW professor of psychiatry Jürgen Unützer said he was heartened to see the increased attention to disability as opposed to an over-emphasis on mortality, as well as the recognition that mental illness is a major contributor to the global burden.
“It appears to me that the years of life lost to depression is three times more than diabetes, eight times more than heart disease … and 40 times more than cancer,” Unützer said. “What that really tells me is we are not doing a good job.”
Mental health, despite its consistently high rankings in the GBD since 1990, has never been a priority in global health, he said.
“There are more psychiatrists in San Francisco than the entire continent of Africa,” Unützer said. The solution isn’t going to be to send battalions of psychiatrists to the developing world, he said, but there are proven programs demonstrating that mental health care can be effectively incorporated into basic primary care programs to beneficial effect.
“One of the more sophisticated things (in the GBD) is how they show how many of these diseases and conditions are all connected, and interact,” said Unützer, referring to the study’s still-emerging interactive data visualization tool. “We should have a global health strategy that also recognizes these connections rather than continue to try to set priorities based on specific diseases or disease categories.”
Finally, the graph to the right shows cancers by type and region.
Based on this, we can conclude that most of the cancer burden that is contributing to the global rise in cancer is still concentrated in wealthier countries.
The GBD’s precision allows for each country to tailor their strategy to meet their regional needs, rather than march to global average.
By comparison, it still appears that Africa’s greatest burden continues to be infectious disease.
As this last graph to the right shows, the leading neglected tropical diseases barely make a showing in most Western or wealthy countries, including some in tropical regions. But they represent a significant burden in many parts of Africa.