Lifetime risk, 1 in 300

In the world of ALS advocacy, there is no shortage of really difficult, even intractable issues. But sometimes you spot some low-hanging fruit, offering the promise of a quick and easy win, and you wonder why we haven’t jumped on the opportunity.

A case in point: We all share the goal of making the public more aware of, and more concerned about, ALS.

We could dramatically improve the impact of public awareness campaigns if we used different, more impactful metrics to describe how common the disease is.

For some reason, the websites of almost every ALS advocacy group in the US use two perfectly accurate but very easily misunderstood epidemiology yardsticks to depict one’s odds of getting ALS. One is incidence rates, or the number of new cases per year, which is 2 in 100,000. The other is prevalence, or total number of people living with ALS. Depending on who is doing this estimation, the prevalence is described as between 15,000 to 30,000 people living with ALS in the US.

Both of these are correct, but make the disease sound really, really rare. But that’s only because the general public isn’t familiar with how to interpret this kind of statistic. The 2 in 100,000 figure is one’s risk of being diagnosed with ALS each year. If the average age of an American is around 80 years, that means one’s odds of dying of ALS are actually a whole lot higher.

A much more impactful statistic would be lifetime risk of being diagnosed with ALS. A colleague in the UK, and a person living with ALS, Lee Millard, reports on a 2006 study in the Journal of Neurology (C. Johnston et al, “ALS in an Urban Setting: A Population Study of Inner City London”) which concluded that the lifetime risk is 1 in 300. One in 300! That is a statistic that has immediate meaning, and packs a powerful punch. A general reader can easily visualize a group of 300 people — it’s the size of typical high school graduating class. If people started envisioning the risk of ALS in the kinds of tangible terms that lifetime risk figures deliver, it would, I believe, raise awareness much more effectively.

In the UK, the flagship ALS group, the Motor Neuron Disease Association, has embraced the lifetime risk statistic of 1 in 300 in its fact-sheet about the disease.

Why aren’t we doing the same in the US?

I understand that some people dispute whether 1 in 300 is accurate, and they may insist on a higher figure. It doesn’t matter. Whether 1 in 300, 1 in 500, or whatever figure the data support, lifetime risk is simply a more powerful way of conveying to the public how much more common the disease is. And it solves the puzzle of how such a seemingly rare disease can be everywhere around us; how almost everyone knows one or several people who have died of ALS.