Forecasting the state of world health in 2050

Can we see the future in the present? How will the world be impacted by conditions including diabetes and other non-communicable diseases? How will environmental changes impact health? The latest Global Burden of Disease Study (GBD) forecasts disease burden scenarios for more than 200 countries through 2050. We discuss the data with study author IHME Director Dr. Chris Murray. 

This transcript has been lightly edited for clarity

Rhonda Stewart: Welcome to Global Health Insights podcast from IHME, the Institute for Health Metrics and Evaluation. I’m Rhonda Stewart. In this episode, we’ll hear from IHME Director Dr. Chris Murray as he discusses new data that provides forecasts for disease burden scenarios for more than 200 countries through 2050. These scenarios provide information in the present that can help shape the future. The research is part of the Global Burden of Disease study, also known as GBD. GBD is the largest and most detailed scientific effort undertaken to quantify health trends. GBD provides a unique platform to compare the magnitude of diseases, injuries, and risk factors across age groups, sexes, countries, regions, and time. For decision-makers, GBD provides a unique way to compare countries’ health progress and to understand factors that impact health, such as high blood pressure, cancer, heart disease, and many other causes. Led by IHME at the University of Washington, GBD is a truly global effort, with more than 12,000 researchers from over 160 countries and territories participating in the most recent update. The latest GBD studies are out now and cover topics including fertility, risk factors, and causes of death. Chris, the study measures trends going out to 2050 and includes a reference forecast, which is the most likely future, as well as alternative scenarios. Tell us a little bit about the main findings of the study and the main findings of the reference forecast.

Dr. Chris Murray: So, Rhonda, in the reference forecast, we’ve tried to capture a host of the key drivers for health. So this encompasses things like growth in income and education, reductions in fertility, changes in all the risk factors that are included in the GBD, including the effects of climate through increased heat, and also changes in air pollution associated with climate change. So when you take all those factors into account, we still see progress in life expectancy and reductions in burden pretty much everywhere in the world. And we see the gaps between the worst-off, particularly in sub-Saharan Africa, and the best-off in the high-income world narrowing, but they still remain disturbingly large in 2050. And we see in these trends that the progress coming is quite a bit smaller the richer you are than the progress in the past generation. So a real slowdown, but still a dose of optimism that despite the challenges we face, things are likely to continue to improve.

Rhonda Stewart: Okay, tell us about each of the four alternative scenarios outlined in the research and some of the key findings. The alternative scenarios include safer environment, improved behavioral and metabolic risks, improved childhood nutrition and vaccination, and then a combined scenario.

Dr. Chris Murray: So what we’ve tried to do, because the forecasting model has a host of causal connections, connections where we believe that that the data from many sources is a true connection, for example, smoking and heart disease and lung cancer. Because we have those causal connections, we can sort of change the trajectory for the future and ask how the future might look different. And this is a dynamic model that is both predicting age-specific rates of death and disability from every condition and aging the population into the future. So you put all that together and we do come up with these different scenarios. And what’s perhaps the most important observation from these scenarios is that the big benefits that can occur are really coming from the behavioral and metabolic risk scenario at the global level. Now, when you go country by country, if you go to poor countries, the improved childhood nutrition and vaccination makes a difference for kids in those places, the safer environment scenario as well. But at the grand scale, at the global scale, the one that really has a very substantial impact on burden, on deaths, on DALYs [disability-adjusted life years], is this: tackling the big NCD [non-communicable disease] risks through behavioral and metabolic risk management. And that's probably the biggest thing that leaps out. There are real opportunities to narrow the gaps between countries and regions and tackle that slowdown that we see in the reference scenario.

Rhonda Stewart: Okay, great. And you touched on this a bit just a moment ago. Tell us more about some of the most striking results with respect to changes and leading causes of death and health loss, and then also some location-specific information in terms of particular countries or regions that stood out in the results.

Dr. Chris Murray: Well, again, back to the sort of cause-specific results, as we’ve seen in the past generation, when there’s been a lot of change in causes, reflecting the real progress on conditions like measles or malaria, some of the childhood killers, big reductions in diarrheal disease, when we look ahead a generation, we also see huge changes coming. And those changes are driven in a large part by the demographic change, the reductions in fertility, the aging of populations, and also continued progress on tackling infections – and at the same time, increases in things like diabetes, driven by the epidemic of obesity. Put all those together, and what we see is diabetes goes up to be the number three cause of burden in the world by 2050. We see big increases for the musculoskeletal disorders. That’s mostly driven by age. We see huge increases in Alzheimer’s and chronic kidney disease and hearing loss and depression, as well as hypertensive heart disease and vision loss. And at the same time, we see big declines expected for malaria, TB, and of course we’re expecting big declines in COVID compared to 2021. So a story of really remarkable transition over a generation. And when we drill down at the country level, you’re seeing that transition sort of happening everywhere. There is a disturbing sort of resistance to change for some of the infectious diseases in many parts of sub-Saharan Africa, where, despite this last generation of progress, we still expect an awful lot of burden from those infections in sub-Saharan Africa, particularly in the Sahel region.

Rhonda Stewart: Okay, it's been 25 years since forecasts were first included in the GBD study. And how have forecasts improved as the picture of diseases and injuries has become more complex?

Dr. Chris Murray: You know, the original forecast model that we produced for the GBD, which was, I believe, published for the first time in The Lancet in 1997, really was an incredibly simple model. It had income, education, and tobacco. And the forecasts weren’t bad at the global level: they mostly got the story right. But now we have a forecast platform that includes all the risk factors in the GBD, these background drivers, depending on the cause, that enhance the predictive validity of the model, and has a complete demographic model. So, if you intervene at a young age and more people survive to age 5 or to age 15, then you have more people aging into future cohorts that get exposed to mental health disorders, injuries, and then if they make it through into later adult life, they get exposed to NCDs. So all those what are sometimes called competing risk relationships are built in, and this allows a much more realistic set of forecasts to be made. It’s a long journey, but I think we are in a much better place to not only produce the sort of results that are in this paper, but to be able to answer the “what if” questions that many governments are starting to come to us and ask. What if we did more on tobacco? What if we had a specific strategy around a particular infectious disease or did something to try to attenuate the increases in obesity? We’re now in a position where we can start to answer those questions in an evidence-based and empirical framework.

Rhonda Stewart: The study’s framework includes models for natural disasters, war and conflict, and migration. But what are some of the challenges that come with modeling those events?

Dr. Chris Murray: Well, you touched on the part that is the least strong in our forecasts. So the natural disaster models are really just looking back in the recent decades and saying, in a particular place for a particular type of problem, what is the rate of those events and holding those constant into the future, as we’re now expecting, at least from storms, we will have rising storms due to climate change. That’s something that we’re going to need to build in in the next iteration. And we do have plans to do that for later this year. For migration, we’ve got models, like others, about international migration. But I think the really big issue for the future is going to be internal migration, again, climate-driven in many cases, which we are also trying to think about how we can capture for next generations. So while we make a bold attempt to capture those phenomena, I’ve got to be honest and say that’s an area where more work is going to improve the quality of that going forward.

Rhonda Stewart: The study also does not include threats that were described as difficult to quantify due to lack of evidence on the potential impacts, or the evolving magnitude of the risk. So bioterrorism would be one example. The study also doesn’t include the impact of advances such as drugs to treat obesity and diabetes, or the impact of AI, for example, artificial intelligence. So how do you expect that these types of threats or advances could be included in future forecasting studies?

Dr. Chris Murray: You know, we’ve gone through a pandemic, and we’ve come out of the pandemic, and suddenly the launch of GPT-4 has put front and center, in a way that has never happened before, the potential of malicious use of AI to be a real threat. We’re in an era where the prospect of nuclear conflict seems more real than it did a decade before. And so we have a number of these threats that should be part and parcel of thinking about future trends that are challenging to model. I co-chair with Natalia Kanem, the head of the United Nations Fund for Population Activities, UNFPA, a Lancet commission on 21st century threats to health, and as part of that work, and as part of this ongoing effort to make the forecasts as useful as possible, we will be trying to tackle modeling some of those threats, albeit some, like malicious use of AI, are incredibly hard to imagine how you can do that in a quantitative way. So even as we make progress on including trends in AMR [antimicrobial resistance], including more pathways of climate change in the forecast, not just heat, including the potential for nuclear conflict, those are all possible to do quantitatively with all sorts of uncertainty and caveats. But some, such as malicious use of AI, might be hard to incorporate. And at the very least, we want to put in front of people, here’s all the things that we have included, and here’s where we think we’re going. And then there’s a shorter list of things that may be very important, may influence the future profoundly, but nobody really has got a way yet to build them into the quantitative models.

Rhonda Stewart: You also said that policymakers and other decision-makers now really come to us and ask those “what if” questions that really highlight how important it is to have these kinds of forecasts. And so how can this information be used to inform policymaking or long-term planning and investment in health?

Dr. Chris Murray: Well, you know, a good, very concrete example is that New Zealand, until they reversed course this year, had decided to legislate a tobacco-free cohort, that everybody born from that day forward would not be allowed to purchase tobacco. And that would basically, over the course of a couple of generations, lead to a tobacco-free New Zealand. And others, the UK government, for example, have been pursuing a similar strategy, and that’s a very exciting initiative. Unfortunately, in New Zealand, they reversed course with a change in government. But nevertheless, it’s an example where we have been asked to model out short- and long-term impacts of such a policy initiative. And it’s a very nice, practical, concrete scenario that is politically possible in some contexts to see enacted. There are other examples of that type of policy question. What happens if you manage alcohol in a different way – higher taxes, less access? What happens to food subsidies and its impact on diet and onto health? A long list of those possibilities. And it’s useful for many governments to be able to say, here’s our idea and here’s how it will impact both future health but also what might be the impact on future health care spending as well.

Rhonda Stewart: And the study focuses on all kinds of challenges and opportunities. So, what is the main thing that people should take away from these forecasts?

Dr. Chris Murray: You know, the main thing is that despite all the media that we have on the ills in the world, this two generations of steady progress in health – with the exception of the COVID setback and the HIV epidemic and the alcohol crisis in Eastern Europe – but at the grand scale, huge progress since 2050, well documented in the GBD demography paper, is likely to continue. And so that’s a message about optimism in the face of extreme pessimism in some quarters about the future, at least for health. And at the same time, the key message that the future is not fixed in stone, and we have lots of opportunities by tackling some of the big risks to alter that trajectory. And I tend personally to think on the NCD risk package, that there are the big three that will really make a big difference to future trajectories of health, namely accelerating the push on reducing tobacco consumption; tackling obesity through diet and physical activity, and also now access to GLP-1s, the new drugs that are very effective for weight loss for some people; as well as tackling the easily managed with existing technologies challenge of high blood pressure. And so there are others in the NCD risk package that we should care about. But those, if we did a good job on those three, we really change the course of future health for low-, middle-, and high-income countries really quite considerably.

Rhonda Stewart: Great. Thanks so much, Chris.

Dr. Chris Murray: Okay.

Rhonda Stewart: And details about the Global Burden of Disease study and a wide range of GBD-related resources can be found at healthdata.org.