A DALY is a measurement of the impact of a disease on a human life. It was developed in the 1990s, but only just recently came to my attention – I’m not sure how (I owe someone a h/t). The World Health Organization goes into more detail:
The YLL basically correspond to the number of deaths multiplied by the standard life expectancy at the age at which death occurs. The basic formula for YLL (without yet including other social preferences discussed below), is the following for a given cause, age and sex:
where:
- N = number of deaths
- L = standard life expectancy at age of death in years
Because YLL measure the incident stream of lost years of life due to deaths, an incidence perspective has also been taken for the calculation of YLD in the original Global Burden of Disease Study for year 1990 and in subsequent WHO updates for years 2000 to 2004.
Seems useful, but the charity research site Give Well has some problems with it:
The DALY metric is used to provide a single number to capture all of the health costs caused by a disease (or averted by an aid program). 1 DALY could represent 1 year of life lost (due to early death), 1.67 years spent with blindness, 5.24 significant malaria episodes, 41.67 years spent with intestinal obstruction due to ascariasis (a parasite), or many possible combinations of these and other symptoms.4 There is no way of knowing, from just how many DALYs a program is said to have averted, whether it has saved lives, prevented large numbers of minor health problems, or some combination thereof.
We feel that this creates a number of problems for donors seeking the charity that best fits their values. More in our blog series on DALYs, available here.
So Give Well would like a dimensional number; this yardstick is a little too simple for them.
I tried to discover if DALYs are used by pharmaceutical corporations to select the next disease to work on, but I found no evidence of such. I suppose those corporations where the execs are wedded to the notion that they exist to make as much money as possible wouldn’t be interested in the concept; it would take a more idealistic executive team, such as we hear about now and then from the Millenials, to consider using DALYs. However, in the category of other factors, companies are often driven by inner competencies, rather than external needs, and so targeted diseases are selected by a less fortunate motivation; and if they are screening drugs against a spectrum of illnesses, then it’ll be fortune that selects the disease to treat.
The Bill & Melinda Gates Foundation funded research to put DALY numbers to a variety of diseases. The results are provided here by the venerable journal The Lancet, and requires a free registration.
