In the beginning (prior to the 1990s), there was a whole mess of data on health and the world. Demographers checked to see who died when, but didn’t care about the why. Epidemiologists watched and tried to stop illness as it spread through the masses, but were uninterested in the overall health of the country. Health agencies looked at childhood death rates, as told to them by government officials, and attacked the biggest killer they could find. And donors forked their money over, trusting it would be spent well.
If this sounds distressingly unorganized to you, you might have a friend in Chris Murray, the workaholic doctor-turned-public-health-statistician with an interest in economics whose brainchild is the DALY. The DALY, which stands for disability-adjusted life years, is a number that allows for the comparison of death and disease on the same scale to figure out which health problems cause the most suffering.
Here is how it works: you take how long a person lived and add that to how much they suffered from an ailment, and then subtract that total from how long they were supposed to live. Is it a big number? That’s bad – it means that due to the health problem the person had, the person missed out on a whole lot of life at perfect health. Here’s an example: Trish developed diabetes when she was 17. Because her diabetes went untreated, her health was only 40% of what it could have been. Her diabetes claimed her life at 32. If she hadn’t suffered from diabetes, she could have lived 76 years at perfect health. Here’s how her DALYs are calculated:
76 years she should have lived – 32 years she did live = 44 years lost
15 years she lived with diabetes × 60% health she missed out on = 9 years lost
Total = 53 years lost
Trish lost 53 years of perfect health because of her untreated diabetes; if you did this same problem with someone else who was, say, suffering from depression over the course of their lifetime, you could compare who lost more years of perfect health and use that to say which problem is worse and therefore deserving of more attention and resources.
This is what Chris Murray set out to do with his Global Burden of Disease project. Looking back at the example of Trish and untreated diabetes, you can see what information is needed to calculate DALYs:
- What the person suffered from
- When they died from their ailment (if at all)
- How long they should have lived
- How living with the health problem compares to living at perfect health
Chris Murray collected data from all sorts of organizations and governments to determine answers for the first three questions and made educated guesses to fill in any gaps in the data. For the fourth question, he organized panels of experts and ordinary people to create estimates; surprisingly, their answers were consistent with one another. And so, for the final comparison, he moved to:
5. Add up all the DALYs for each health problem
This last step allowed him to look at the disease burden in the world and compare each health problem on the same scale… and a surprising picture emerged. Sure, infectious diseases like malaria were claiming tons of healthy years in the developing world – but so were motor vehicle accidents and depression. Because of the DALY, Chris Murray was able to show major health organizations that focusing all of their funding on childhood diseases and neglecting the health problems that adults face wouldn’t save the most healthy years; redistributing some of those funds to address chronic depression and car accidents would be a more efficient use of the available resources.
Clearly, DALYs are a powerful tool. Murray was able to take existing data and sort it out to create a numbers-based comparison to inform funding initiatives. But if the DALY is an inaccurate measurement, it would create an inaccurate picture. The DALY measurement is colored by the culture it was created in; what counts as a health problem varies from culture to culture, so if we are talking about global improvement, there is a need to incorporate a global perspective. It also is ableist, as people and experts who may not have had a direct experience with the health problem they were judging decided how bad it would be to live with that ailment. Studies have shown again and again that happiness and satisfaction with life are relative, so the judgement of quality of life should come from those living with that health problem. Finally, there are morally troubling consequences of taking human suffering and putting it on a scale. The depth and significance of human suffering cannot be explained with a single number. And given that health organizations around the world use these numbers to determine what gets funding and what doesn’t, these numbers are ultimately used to determine whose life is worth saving.
However, we have the luxury of talking about the moral qualms of the DALY as we watch the world go by from the proverbial armchair. Murray saw that a huge amount of funds (90% of them) were going to 10% of the world’s problems, which is a gross misapplication of funds in anyone’s book. The DALY isn’t perfect. The way we measure health and put it all on one scale is morally upsetting. However, in the end, it is better to do more good than less or none at all, and the DALY helps achieve that.