Thursday, 8 August 2013

Research Cohorts

Long days at the wheel give me time to think. I don;t know that this is always a good thing. Yesterday was one of those days. Driving through northern Ontario, along The King's Highway 11 as they call it here, was a multi-hour stretch of soft twist and turn on a road cut through the rocks of an ancient mountain range ground down to rock, across hundreds of small rivers and streams, around dozens of lakes, all surrounded by scrub green trees of mixed hue and type. For most of the day it was a drive in the midst of trees, rocks and water, with the odd village sprinkled along the way for distraction. There were a few larger towns of course, but mostly it was wilderness. It was neither boring nor monotonous; it was smooth and easy.

So I got to thinking, and yesterday I thought about the challenges of ALS research. It is a numbers game more than anything. Researchers estimate that roughly 1 in 10,000 people will get ALS. Compare that with cancer where researchers estimate that 1 in 20 people will get cancer. According to the CDC, there were roughly 12.5 million Americans with cancer, all types combined, while there were between 20,000 and 30,000 people with ALS.  No wonder cancer gets more press, and more research. For every PALS there are 500 cancer patients.

You might wonder why the ALS numbers are so "approximate". Firstly the ALS population is not well measured. It is a disease that masquerades itself; diagnosis is difficult and in many cases, incorrect. ALS is a guerrilla fighter in the disease jungle, a small moving target, mostly hidden, unseen, terrorizing only a few. People have ALS and don't know it until long into their progression. Secondly, we die at a persistent and consistent rate; about one-quarter to one-third of PALS die each year. Some live longer, some shorter, but the mortality rate across the group is fairly steady. We die at an alarming rate.

This makes research very difficult. To understand a disease, researchers need a consistent and relatively large "cohort" to study; this means a relatively large group of PALS with similar onset, similar symptoms and long enough life-spans to study. As PALS with a disease that is highly variable in onset and progression, with a short life expectation, it is almost impossible to get a decent sized research cohort for any given research site.

Take my case as an example. The doctors think I have PMA, a form of ALS that affects about 4% of all PALS. Of the roughly 500,000 people globally with ALS, my variant has a cohort of approximately 20,000 people. That is globally. Imagine trying to arrange a world wide research study with that population, and then imaging roughly a fourth of them dying every year. In the US there are only 1,000 PALS with PMA and in Canada only 100. There just are not enough PALS, and I thank God for that.

This is just some of the thinking I did yesterday. There were many more hours to think, many more hours of trees, rocks and water, many more hours to calculate and wonder. All I could conclude was that I am unlikely to live long enough to see any major advances towards a cure for this awful illness. That will come for someone in the future.

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