Q&A: Populations are now living longer, but not necessarily in better health

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This transcript has been lightly edited for clarity

Your paper studies the global burden of disease since 1990. What is meant by "burden of disease", and can you explain the health metrics DALYs and HALE, used in your study?

The GBD study uses the disability-adjusted life year, or the DALY, as its main metric to measure disease burden – or health loss, essentially. And to estimate the DALYs for a particular cause, or disease or injury, we take both the morbidity, or the disability, associated with that disease, combined with the mortality – the years lost to premature mortality – associated with that disease as well. HALE is essentially the opposite of the DALY. We leverage what we know about the morbidity and the mortality within a given population to estimate the years spent in good health as opposed to poor health.

What are the headline takeaways from your research into the burden of disease since 1990?

There’s a lot to digest from GBD 2021 in terms of trends in disease burden globally. There are a few things I’d like to highlight here. First off, between 1990 and 2019, we’ve seen rather encouraging and consistent improvements in disease burden, largely due to reductions in vaccine-preventable deaths and reductions in under-5 mortality rates.

What this has meant in 2021 is we’ve seen a shift in the drivers of disease burden globally, from communicable diseases now to non-communicable diseases coming to the fore. So, stroke, ischemic heart disease, COPD, diabetes, for example. So what that means is although populations are now living longer, they’re not necessarily living in good health. And we need to pay attention to those non-communicable diseases, as well as continuing gains made to communicable diseases, such as HIV/AIDS, as we move forward.

The second trend I’d like to highlight from GBD 2021 is that it provided us with an opportunity to look at the impacts of the COVID-19 pandemic. GBD 2021 estimated burden for both 2020 and 2021, and there we saw COVID-19 emerge as a leading cause of disease burden for those years. 

How did COVID-19 impact what was happening with burden of disease trends after 2020?

What we saw for the first time in 30 years, in 2020 and 2021, was an increase in age-standardized DALY rates at the global level due to the COVID-19 pandemic.

We saw, as I said before, COVID-19 emerge as the fourth-leading cause of disease burden in 2020 and the leading cause of disease burden in 2021, largely due to deaths from COVID-19 in those years. Over and above that, GBD 2021 also looked at burden from the long-term, secondary consequences of COVID-19. We saw additional burden from long COVID, as well as additional burden from the mental health consequences of the COVID-19 pandemic, so added burden from depressive and anxiety disorders as a result of the pandemic.

Did you see any gender differences in burden of disease trends in the period studied?

Different diseases and injuries will come with different trends when it comes to both sex and age. But we were talking about COVID-19 just before. And what was interesting there was that, although males and females were impacted largely in the same way when it came to COVID-19 infections, we saw a larger burden from COVID in men compared to women, and that was because men were more likely to die from COVID-19 compared to women. However, when we when it came to the long-term consequences of COVID-19, we saw the opposite effect: women were more likely to be impacted by long COVID. They were also more likely to be impacted by the mental health consequences of the COVID-19 pandemic, compared to men.

How did HALE at birth change during the period studied, and why is it an important metric to understand?

Overall, we’ve seen improvements and continue to see increases in HALE between 2010 and 2021, say. 

And that is in spite of a decrease in HALE of about 1.4 years during the two COVID years, so during 2020 and 2021. These HALE results serve as a new baseline  for years to come as we continue to recover from the COVID-19 pandemic, as the sociodemographic circumstances of different countries change, hopefully for the better. As life expectancy improves, we expect to continue to see this increasing trend in HALE, so GBD 2021 serves as an important baseline for that.