Elie thinks that fistula is worse than death. jsalvati disagrees.

I’d rather bring someone to full health than save an infant’s life. Ryan agrees, but Basti does not and Ron Noble emphatically does not.

It’s possible that we would all agree if we knew more about the lives of people in the developing world, or if we just had a long enough to argue about our values. It’s also possible that we wouldn’t. And as long as we disagree, we’ll have different opinions on what the most “cost-effective” interventions are. For example, if it’s true that fistulas can be repaired for $450 each, is this a better or worse use of donations than preventing children’s deaths for $200 each through vaccinations? My answer would be “It depends on the donor.”

Converting disease burdens and intervention benefits into DALYs doesn’t resolve questions like this. Rather, it obfuscates them, by converting the two interventions into the same terms using a single set of philosophical values. If the numbers above ($200/death averted for vaccinations, $450/surgery for fistula) are accurate, they allow different donors to make their own judgment calls, while being informed about their options. But these aren’t the numbers you’ll find in the Disease Control Priorities Project’s summary tables; instead, you’ll see only that surgical services cost an average of $136 per DALY averted (Jamison et al. 2006, Pg 75) and that the vaccinations interventions costs an average of $7 per DALY averted (Jamison et al. 2006, Pg 77).

Some simplification and information loss is necessary in order to compare different options, but reducing everything to a single unit means being able to serve only a single kind of donor. I’d prefer to estimate the effect of different interventions on a variety of “life outcomes” that different donors might value differently. We will discuss this variety more in a future post, but here’s a quick list:

• Total life-years saved.
• Adult lives saved (as it is common to value adult lives more than children’s lives).
• Cases of extreme misery, such as fistula or perhaps severe elephantiasis, averted.
• People brought to a “normal” level of health, i.e., without any debilitating nutritional or other conditions.

All of these things need to be separately estimated to produce DALY estimates. The DCP report did so with admirable thoroughness and far more people than we have (Jamison et al. 2006, Pgs xxiii-xxxiv). Yet because they published only their DALY estimates (not, with some exceptions, the estimates of different health problems that went into them), they buried a great deal of this work, and produce cost-effective estimates that are useful only if you’re completely on board with all of their values (from how bad each disability is to how to value different years of life). We’re currently trying to get in touch with the authors so we can get access to more of the details; if we don’t, we’ll have to repeat much of their work (with less capacity to do so).

Sources

• Jamison, Dean T. et al., eds. 2006. Disease control priorities in developing countries (2nd Edition) (PDF). New York: Oxford University Press.

Previously in series:

• Disability-Adjusted Life Years: Introduction
• Disability-Adjusted Life Years II: Variations

Coming across the current feature on the DCPP’s home page reminds me of how much I care about the issue of obstetric fistula.

The following are highlights from the article linked above (emphasis mine):

For countless women in developing countries, going into labor is the painful beginning of a lifetime of unremitting shame and misery as a despised social outcast—destitute, childless, and abandoned by family and friends.

These women have a condition called obstetric fistula. A fistula, the Latin word for “pipe,” is an “abnormal passage” between organs — in this case, between the vagina and the bladder, the rectum, or both. The hole makes the woman uncontrollably incontinent of urine or feces or both and transforms a healthy person into someone viewed as a leaking, reeking, “moving latrine,” in the words of Veronica Yakobe, a Malawian woman who endured 23 years of indignity before an operation at Nkhoma Hospital in her country’s central region closed the fistula.

• 2 million to 3.5 million women worldwide currently [live] with obstetric fistula.
• Statistics from Ethiopia, Nigeria, India, Pakistan, and elsewhere show that the majority of fistula sufferers are abandoned by their families, divorced by their husbands, and forced to fend for themselves, often by begging. Some, like a group of Somali women who leapt from a pier chained to one another, end their lives in despair.
• Studies of patients undergoing fistula surgery find the majority in their early twenties or younger. In one Nigerian study, 72 percent were between the ages of 10 and 20, 82 percent having married between 10 and 15.
• A number of facilities, most prominently the renowned Addis Ababa Fistula Hospital, in Ethiopia, repair thousands of fistulas each year at a cost of about $450 for each operation and related care.

The disability weight used for fistula in DALY calculations is .430 (Pg 121 of the Global Burden of Disease report (PDF)). For context, the disability weight for blindness is .600 (Pg 120). To me, fistula seems much worse. Not only does a person undergo severe physical trauma, but she also often suffers severe social consequences such as communal ostracization and abandonment by her family.

In fact, it’s hard for me to imagine a cause I’d rather attack. I’d much rather prevent a fistula than save a life. The fate described above seems worse than death.

We’re planning to look into fistula carefully, and I hope we’ll find donors a great option for helping those afflicted.

Previously, I outlined the basics of the Disability-Adjusted Life Year (DALY) metric. It takes the approach of converting all health burdens into equivalent “years of healthy life lost”: a year of blindness is counted as .6 lost years, a year of severe malnutrition is counted as .053 lost years, etc.

This post discusses two common “variations” on DALYs, meant to deal with relatively thorny disagreements about how different years of life should be valued. As before, page numbers refer to the Global Burden of Disease 2000 report.

Age-weighting

One variation has to do with the intuition some people have that a 20-year-old’s death is more tragic than an infant’s. (I expressed this intuition myself back in November, and I still hold this view.) In an attempt to square with this intuition (which is common and well-documented, as Pg 400 shows), the DALY metric includes an optional age weighting feature that lowers the value of a healthy year of life lived at very young and very old ages, relative to the value of a healthy year of life around age 20. DALYs can be computed with or without age-weighting (”without” just means that all years of healthy life are valued the same).

Discounting

The other variation has to do with valuing present vs. future benefits of aid. DALY calculations apply a discount rate to future benefits; for example, when using a discount rate of 3%, one would count a year of healthy life saved ten years from now as being worth only 74% as much as a year of healthy life saved this year (74% = 1/1.03^10).

I confess that I don’t fully follow the justification for discounting given in the Global Burden of Disease Report, which claims that “the strongest argument for discounting is … [that] not discounting future health would lead to the conclusion that all of society’s health resources should be invested in research programs or programs for disease eradication” (400), which apparently is considered obviously wrong by the authors. Personally, the most appealing argument I can think of for discounting is that helping a person can help them help others, so helping a person sooner is literally “worth more” than helping a person later.

Notation

DALYs(0,0) refers to DALYs calculated with a 0% discount rate and no age-weighting. DALYs(3,1) refers to DALYs calculated with a 3% discount rate and age-weighting. (The first number in parentheses is the discount rate; the second is a 1 if age-weighting is being used, and a 0 if not.) See Pg 401 for the specifics of how varying these numbers affects the valuation of different years.

In theory, you can calculate DALYs using whatever parameters best fit your own philosophical values. In practice, the reports we’ve seen using this metric (Global Burden of Disease Report, Copenhagen Consensus, Disease Control Priorities Project) will give you, at most, DALYs(0,0), DALYs(3,0) and DALYs(3,1), and will rarely give you the inputs into these numbers so you can calculate your own versions. That means that if you want to use a 6% discount rate, you’re completely out of luck; there’s no way to convert DALYs(3,0) to DALYs(6,0) without having more information. More importantly, it means that:

• You can’t use your own version of age-weighting. Even the age-weighted version of DALYs still rates an infant death as about equally tragic to a 20-year-old death (it values a year more for a 20-year-old, but when you work it all out the value of a life comes out the same). There is evidence (see pg 401) that people find a 20-year-old’s death to be far worse; if you share that intuition, then DALYs as they are usually presented won’t reflect your values, and there will be no way to convert them into a unit that does.
• You can’t use your own disability weights. Personally, this is the area I’d most like to see some variation in - the official disability weights disagree violently with my personal intuitions about, for example, how bad it is to be severely malnourished (current weights put it at only 5.3% as bad as a year of life lost - see Pg 121) or how bad it is to go through an abortion (it appears that this is counted as “no cost” by DALYs - see Pg 121 again).

The DALY metric does have some flexibility to accommodate different personal values, but in practice it ends up being pretty rigid. More on this in a future post.

Next in series:

• DALYs and disagreement

Previously in series:

• Disability-Adjusted Life Years: Introduction

We’ve had many discussions in the comments about the metric known as Disability-Adjusted Life-Years (DALYs). The DALY essential converts the burdens imposed by all health issues - from premature death to blindness to injuries - into a single, consistent unit. It is the metric of choice for the Disease Control Priorities Project as well as a centerpiece of the Copenhagen Consensus analysis, and is used widely by the World Health Organization - yet it isn’t, and likely won’t, be the central metric in our analysis.

At this point I want to start a more thorough discussion of why this is. I’m going to start at the beginning, with a full description of what DALYs are (and the different ways of calculating them). Some readers will already be familiar with what’s below, but we want to make sure we clearly describe the metric and give examples of its implications before discussing its strengths and weaknesses.

The most complete account of DALYs I know of is in the Global Burden of Disease report. Page numbers below refer to this report.

The basics: burden of health problems in terms of years of life

A DALY is a measure of the “burden” of a health problem; two common uses of this measure are (a) ranking diseases and risk factors (from most to least burdensome), as the Global Burden of Disease report does, and (b) ranking different interventions (in terms of how much they can be expected to reduce burdens, “per dollar”), as projects including DCPP do. The basic DALY formula is on page 48:

DALY = YLL (Years of Life Lost) + YLD (Years of Life lost due to Disability)

YLL is the more straightforward component. Putting aside discounting/weighting issues (to be discussed later), the death of a male infant (life expectancy 80 years) would be counted as 80 years of life lost, while the death of a 45-year-old female (life expectancy 83.72 years) would be counted as 38.72 years of life lost (see page 402 for the life expectancy figures). Without further adjustments, this implies that the death of a single infant is considered about as bad in and of itself as the death of two adults.

Quantifying morbidity

YLD represents an attempt to convert years of life affected by a disability into the same terms as years of life lost due to premature death. For example:

• A year spent with blindness (as opposed to a year spent with “normal health”) is counted as 60% as “bad” (i.e., as much burden) as a year of life lost due to premature death. So the metric would count a condition that permanently blinds five 30-year-olds as about equally “burdensome” to a condition that results in the death of three 30-year-olds.
• A year spent with protein-energy malnutrition to the point of wasting (i.e., being severely underweight) is counted as 5.3% as “bad” as a year of life lost due to premature death. This implies that if a child is malnourished to the point of being severely underweight and having a lower life expectancy (say 30 years), the burden in DALYs is equal to about 51.59 (50 years of life lost due to early death; 30 years of malnutrition * 5.3% = 1.59 YLD), which is about 60% the burden of an infant death.

As for where these numbers come from (why is a year of blindness 60% as bad as a year lost, and a year of wasting 5.3% as bad?), they were obtained through a variety of methods usually involving surveying groups of people on their subjective attitudes (Pg 50 has more on this). The complete list of disability weights - giving a conversion factor for every kind of health condition analyzed by the GBD - is found on pages 119-125.

This basic framework - evaluating all health burdens in terms of “life-years,” with a year lost to death counted as a full year and a year otherwise afflicted counted according to the disability weights - is common to all DALY calculations. In the next post on this topic, I’ll discuss some of the variations between different versions of DALYs; some versions “discount” life-years that are early in a person’s life, late in a person’s life, or far in the future. After that, I will explain what we think the limitations of this metric are as it applies to our work.

Sources

• Copenhagen Consensus Center. Copenhagen Consensus 2008. http://www.copenhagenconsensus.com/Home.aspx (accessed April 15, 2010). Archived by WebCite® at http://www.webcitation.org/5p0sJczhJ.
• Jamison, Dean T. et al., eds. 2006. Disease control priorities in developing countries (2nd Edition) (PDF). New York: Oxford University Press.
• Lopez, Alan D. et al., eds. 2006. Global burden of disease and risk factors (PDF). New York: Oxford University Press.
• World Health Organization. Global burden of disease (GBD). http://www.who.int/healthinfo/global_burden_disease/en/index.html (accessed April 15, 2010). Archived by WebCite® at http://www.webcitation.org/5p118giwH.

Next in series:

• Disability-Adjusted Life Years II: Variations
• DALYs and disagreement