Dive into the latest trending topics in global health with IHME's Global Health Insights blog. Our health researchers explain the significance of new studies, share data related to current events, and help you understand the story behind the numbers.
November 22, 2022: World Antimicrobial Awareness Week
- A short list of pathogens account for a large fraction of bacterial-related deaths. The main causes include S. aureus, E. coli, S. pneumoniae, K. pneumoniae, and P. aeruginosa.
- These pathogen estimates are immediately relevant to groups concerned with the development of new antibiotics and new vaccines, such as research and development investment groups, the research authorities of different countries, and private sector investors in the pharmaceutical industry.
- There may be a mismatch between R&D investment spending and disease burden. For example, $42 billion in the last two decades or so was spent on HIV, while the spend on a major bacterial pathogen like E. coli was only about $800 million. Yet the burden of E. coli is only a little bit smaller than the burden of HIV.
- Prioritizing infection prevention is important through measures such as risk management, infection control in hospitals, and deploying existing vaccines (like the vaccine for strep pneumo) more widely.
This transcript has been lightly edited for clarity
IHME Director Chris Murray: In this week's Global Health Insights, we're going back to the body of work that we started earlier this year when we published on the burden of disease due to antimicrobial resistance around the world, due to 88 bug-drug combinations. The big database that we put together on the distribution of key clinical syndromes - pneumonia, bloodstream infections, intra-abdominal infections, others. By pathogen, we have now analyzed, not looking for the resistance patterns, but just getting a deeper understanding of what the role of 33 different bacterial pathogens are in infectious disease deaths.
And that is really groundbreaking, because we tend to see in global health the burden of disease grouped by either some specific pathogens, like malaria, or syndromic clusters, like lower respiratory infections or neonatal sepsis or bloodstream infections. But by going in and looking at all the data, using the appropriate statistical methods that have been developed, to try to use all the rich data that's out there to understand pathogen distributions. What we can reveal is the role of some bacterial pathogens that are probably hidden from people's sight in the general global health discourse. So it turns out that as we look across pathogens, there's a short list that accounts for a large fraction of bacterial-related deaths. So some of the main causes there are Staph aureus, E. coli, Strep pneumoniae, Klebsiella pneumoniae, and Pseudomonas aeruginosa, but also important roles for some of the other bacterial pathogens.
Research spending mismatch for bacterial pathogens
This pathogen view is important and it's immediately relevant to those groups who invest in research and development, the research authorities of different countries, NIH, for example, as well as to the investments from the private sector in the pharmaceutical industry, in the development of new antibiotics and new vaccines.
And in fact, there have been other research that's been done that has tried to count in the last 20 years or so the spending on global pathogens. And when we compare that spend, for example, $42 billion in the last two decades or so for HIV, to the spending on some of these major bacterial pathogens like E. coli, that spend is only about $800 million. And yet the burden of E. coli is only a little bit smaller than the burden of HIV. And so I think this pathogen view of the world, or in this case bacterial pathogen view of the world, reveals that there may be a mismatch between how the R&D investments around the world in drugs and vaccines and diagnostics as well is not necessarily aligned with where all the burden is.
We also think it's important to take a pathogen view of the world for thinking about prioritization around preventing infection where that's possible through either risk management, infection control in hospitals, as well as deploying those vaccines that currently do exist, like the vaccine for Strep pneumo more widely. And of course, if we eventually do see new vaccines come through the R&D pipeline, recognizing that there is a real opportunity to reduce harm around the world.
Taking a pathogen-specific view on the burden of disease
So this focus on pathogens, in this case bacterial pathogens, comes out in our new paper in The Lancet. We do see further work in the future coming, looking at all of the pathogens together, not just the bacterial pathogens, to bring that pathogen-specific lens to the world. About a quarter of all DALYs, a major pathogen is involved, whether it's the ones that are directly assigned as underlying cause, like HIV or malaria, or the role of many of the things in this study, bacteria in deaths from some of the chronic diseases such as diabetes, where a diabetic may die from a gram-negative sepsis in the hospital.
But having that pathogen-specific view will give us another insight into the targets for intervention as well as for R&D. It also, I think, helps get a sense in different parts of the world of, we put a lot of emphasis, appropriately so, on HIV, TB, and malaria. But we probably need to pay as much attention to something that's quite neglected, like Staph aureus, that's affecting poor countries as well as rich countries.
And so I think there's a lot to be learned about a different perspective on the burden of disease that's brought about by this analysis. So expect more in our future Global Health Insights both on the sort of pathogen perspective, how does that look as we go into the future in terms of forecasting trends, given what we know is maybe some of the important changes in the disease profile in different parts of the world? And how do factors such as climate change intersect with the burden due to specific pathogens, that may actually be affected by environmental heat temperature and other factors? So more to come on these sort of evolving understanding of different drivers of burden around the world.
November 17, 2022: Global population reaches 8 billion
- We expect the population to peak in about four decades, somewhere over 9 billion, and then begin to decline.
- In sub-Saharan Africa, fertility rates remain high, so the population will continue growing until the end of the century.
- In almost all other regions, the fertility rate is below replacement level.
- Lower fertility levels creates an inverted population pyramid, meaning a greater percentage of people in the population are older.
- With more grandparents than grandchildren, there will be significant societal impacts that must be accounted for.
- Some options to address below-replacement fertility levels:
- Increase support for parents through programs like subsidized childcare and enhanced parental leave.
- Welcome migrants to solve the gap in workforce created by aging populations.
This transcript has been lightly edited for clarity
November 15th is the day that the UN is celebrating global population reaching 8 billion and that has certainly occurred sometime this year, if not in the recent weeks. And the real question for us all is what does it mean and where is population going in the world? In our assessment at the Institute for Health Metrics and Evaluation, which is part of this new Global Health Insights, is that global population will peak in the 2060s, somewhere over 9 billion, and then begin to decline.
Continued growth in sub-Saharan Africa
But to understand population and its consequences, we need to look at the world in two groups. In sub-Saharan Africa, total fertility rates and the patterns of fertility in completed cohorts of women remain quite high. In parts of the Sahel, the total fertility rate is over seven. In other parts of East Africa and South Southern Africa, total fertility rates have declined substantially and some countries are below four, and we expect those declines to continue.
Declining fertility in the rest of the world
Nevertheless, those higher fertility rates in sub-Saharan Africa mean that we expect the population of sub-Saharan Africa to continue growing right towards the end of the century. That's in sharp contrast to what we're seeing everywhere outside of sub-Saharan Africa – with few exceptions. In places like China, the total fertility rate is now down as low as 1.1, with similar numbers in Japan, in Korea, in Taiwan, and in Singapore. We've seen India, the second largest country in the world, drop below replacement fertility in the past year.
So the pattern of below replacement fertility is now the norm outside of sub-Saharan Africa. And in the course of the next generation will become essentially the true in all countries, with few exceptions, outside of sub-Saharan Africa. This could be thought to be good for the planet – fewer people, less climate stress, but it comes with other consequences that societies are going to have to manage as fertility drops to these lower levels.
And we expect from our analysis that once women are educated and have access to pursuing careers and have access to reproductive health services, they tend to want to have about 1.4 children on average. Now, of course, there'll be a lot of cultural variation in that, but it's that average number that matters because 1.4, it means that with each generation, the population will get smaller.
Societal implications of an aging population
That creates an inverted population pyramid where there are more people in the age group ahead of you than behind you. This has all sorts of ramifications for how do governments balance the books? Who pays the taxes to pay for health insurance, social insurance? Elder care? How do economies work when it's younger workers that tend to buy homes? So what will happen to the real estate market as populations go into decline?
And there's faster decline in the younger age groups than in the older age groups. There will be societal impacts when there are more grandparents than grandchildren, and the knock on effects are things that we don't fully understand. And at least for the next 50 years, countries have two options in the set that have below-replacement fertility.
How to address it
One option is to support women and having children, the number of children they want to have as well as pursue careers. And that's sort of the pattern that's been used in northern Europe. Subsidized childcare, maternity leave, paternity leave, guaranteed rights to return to your job after pregnancy. That package of interventions and that can increase the fertility rate maybe by 0.1 or 0.2 children.
So that's a benefit, but unlikely to bring you back to replacement in those societies. The other strategy, at least for the next 50 years, is to welcome migrants and you can solve your gap in the workforce. Keep the number of workers up and the tax base for societies up by having liberal immigration policies. And many countries will successfully pursue that.
Countries like Canada, Australia, and New Zealand have been pursuing that sort of immigration policy for decades, and they've managed to keep their population numbers and workforce up and/or actually increase them in some cases. Some countries are not very enthusiastic about bringing in migrants and yet have low fertility – China, Russia, many other countries. And they will face the biggest challenges, and we worry a lot in those settings that they will be tempted in some settings to rollback women's reproductive health rights as a strategy to increase fertility.
And of course, that would not, in our view, be a good thing. It would be a setback for women. And so the global community really needs to be providing solutions for all countries about how to manage the challenges of low fertility. Are there strategies that reinforce women's right to choose on their family size? Let them pursue careers that will also help reduce the sort of dramatic reductions in population size that are possible.
The impacts of climate change
In sub-Saharan Africa, it's a different story, particularly in the Sahel region, where we expect they will be the first places in the world to face climate change impacts in the form of reduced agricultural input, heat stress in some settings in the Sahel. Some localities may not be habitable anymore as the number of days above some high threshold of temperature become intolerable.
So we do expect the combination of high fertility, climate stress in the next generation to likely lead to mass outmigration from some of those settings, either north across the Sahara or even more likely south from the Sahel belt into countries south of the of that belt. But some of those countries will also be facing the impacts of climate change.
So the world needs a nuanced approach to thinking about population. The role of population forecasting and scenario building becomes important, especially as we learn more about the options available outside of Africa to increase fertility or promote migration. And within sub-Saharan Africa, the strategies are a little bit more clear. Get women access to contraception and reproductive health services, as well as enhance the education of women, which remains really quite low in some parts of the Sahel particularly. Expect more in our Global Health Insights in the future as we try to take the modeling here at IHME – the forecasting, the scenario building, and look at some of the other threats to human health and prosperity around the world in the coming editions of the Insights.
October 14, 2022: Burden of Proof
- We designed the Burden of Proof study to help consumers makes sense of confusing health guidance by assigning a star-rating to pairs of risks and outcomes.
- We reviewed thousands of studies on risks like smoking and eating red meat to determine how strong the evidence was that those risks lead to health impacts, and whether it’s worth changing your behavior.
- Five-star ratings – like smoking & lung cancer and high blood pressure & heart attacks – indicate that there is strong evidence of association.
- One-star ratings indicate that there may be no association at all, or that more evidence is needed on the topic.
This transcript has been lightly edited for clarity
This is a project that started nearly five years ago where we were looking at all the controversy in the literature, both in the media and in the scientific literature about certain risk-outcome associations. It started with diet, but there's also a lot of controversy around air pollution and controversy about other associations. And we wanted to find a way to help the public, to help research funders and to help decision-makers in government navigate this very confusing field.
Remember back to the Time magazine cover about Don't Eat Bacon a few years back. And, you know, this is happening all the time. You see one study swinging you in one direction, another study swinging you back. And so we really wanted to find a way to help everybody navigate that complexity. So the burden of proof study is our attempt to look at all the evidence that's out there on a risk-outcome relationship.
We've done this for nearly 200 risk-outcome pairs and try and figure out how strong is the evidence and to rate the strength of that relationship on a five-star scale from one star where the average interpretation of the evidence is that it's either harmful or protective. But perhaps if you take a conservative view of the evidence, there's no relationship at all.
Right through to the five-star association where there is overwhelmingly convincing evidence of the risk-outcome relationship. The key findings is that we see a really wide range of strength of evidence around these relationships from smoking and lung cancer or high blood pressure and heart attacks, which are five-star relationships down to quite a large number of relationships – many of them are between diet or components of diet and outcome – where the relationships are not very strong at all.
In fact, in the case of the one-star associations, they may simply be something that will change in the future as a new study comes along. And so the conservative view of those is there may be no relationship there at all.
I think the most surprising aspect of the findings is that there are some associations, think about red meat and heart attacks or physical activity and diabetes, that many of us took as grounded in really strong evidence. But at the end of this process of looking at the thousands of articles that we review and then coming up with this overall assessment of how strong is the evidence and risk and outcome relationships.
Some of those things that we were very convinced about in the past turn out to not have such compelling evidence behind them. If you start with the associations at the other end of the spectrum, the five-star or the four-star or the three-star associations, these are things that everybody who's concerned about their health will want to take into account and to avoid them if they're harmful and to embrace them if they're good for you or protective.
When you get into the zone of the two-star and the one-star associations, then it's going to be more about your personal risk tolerance. If you are somebody that really is risk averse and wants to avoid any possible risk to their health, you'll want to avoid the harmful one-star and two-star risks and embrace the protective one- and two-star associations.
But if you are somebody that's willing to accept some risk or that there might be risk, then you can take a more nuanced approach to how you view a one-star association. Personally, for me as an individual, I'm not going to change my behavior for a one-star associate. But I'm probably going to act on two stars and above.
So we see this burden of proof, risk, function, work, and the star rating is something that we are going to keep up to date so that the public has access to this sort of assessment on a regular basis and can feel confident that it reflects our current knowledge. And there will be or are associated online tools for those who are motivated to get into the details and see what studies are out there and how it is we've come up with our assessment around the star rating for risk-outcome relationship. So we hope this is a service to the public and will continue into the future.