What constitutes a disease?

A healthy debate rages as to whether Restless Legs Syndrome is actually a disease, or whether it was something contrived by drug companies in order to sell drugs.

Nicholas Wade reports in the NY Times that two separate studies have found a gene that is linked with the disease:

Kari Stefansson, chief executive of Decode Genetics, said his company had linked variations in the gene known as BTBD9 with periodic leg movements during sleep and with low iron levels in the blood, two clinical features already associated with the syndrome. He said Decode had missed, but subsequently confirmed, the two other genes identified in Dr. Winkelmann's study.

Experts find it hard to assess how common restless legs syndrome is because it covers a broad spectrum of symptoms, the milder forms of which are harmless, and is also mimicked by several other diseases, like nocturnal cramps. Dr. Stefansson said he believed restless legs syndrome occurred in 5 percent to 15 percent of European populations. Dr. Woloshin said the "most credible" estimate is 3 percent. Still, even that proportion could mean that a lot of spouses are getting kicked out of bed every night.

The variant form of BTBD9 is very common but in most people causes no symptoms. But it accounts for 50 percent of cases of restless leg syndrome in European populations, Decode Genetics calculates. The prevalence of the disease varies widely between ethnic groups, being found in only 0.1 percent of Singaporeans and 2 percent of Ecuadoreans.

This is reassuring, but if you have experience with poly-genetic diseases you know that you can find genes that are linked with a lot of things. Establishing causality is another matter entirely.

Some scientists are not convinced. As the Freakonomics Blog reports, Woloshin and Schwartz writing in PLoS Medicine question whether the prevalence and the benefits of treatment have been exaggerated in the media. They argue that pharmaceutical companies have suckered the media to sell their drug for them:

"Disease mongering" is the effort by pharmaceutical companies (or others with similar financial interests) to enlarge the market for a treatment by convincing people that they are sick and need medical intervention [2]. Typically, the disease is vague, with nonspecific symptoms spanning a broad spectrum of severity--from everyday experiences many people would not even call "symptoms," to profound suffering. The market for treatment gets enlarged in two ways: by narrowing the definition of health so normal experiences get labeled as pathologic, and by expanding the definition of disease to include earlier, milder, and presymptomatic forms (e.g., regarding a risk factor such as high cholesterol as a disease in itself).

After studying the coverage of RLS, they recommend the following to improve coverage:

First, journalists should be very wary when confronted with a new or expanded disease affecting large numbers of people. If a disease is common and very bothersome, it is hard to believe that no one would have noticed it before. Prevalence estimates are easy to exaggerate by broadening the definition of disease. Journalists need to ask exactly how the disease is being defined, whether the diagnostic criteria were used appropriately, and whether the study sample truly represents the general population (e.g., patients at an insomnia clinic cannot be taken to represent the general public).

Journalists should also reflexively question whether more diagnosis is always a good thing. Simply labeling people with disease has negative consequences [21]. Similarly, journalists should question the assumption that treatment always makes sense. Medical treatments always involve trade-offs; people with mild symptoms have little to gain, and treatment may end up causing more harm than good.

Finally, instead of extreme, unrepresentative anecdotes about miracle cures, journalists should help readers understand how well the treatment works (e.g., what is the chance that I will feel better if I take the medicine versus if I do not?) and what problems it might cause (e.g., whether I might be trading less restless legs for daytime nausea, dizziness, and somnolence).

You will get no resistance from me on those points. I always think that journalists should be more skeptical of scientific research, much less press releases. Particularly with respect to side effects, the media tends to ignore that any use of medication is a cost-benefit decision.

However, I am curious about their implications of the mechanism for this distortion. I am sure that GlaxoSmithKline, the makers of the RLS drug ropinirole, would like to sell more drug. I am sure that they are willing to exaggerate their market in order to do so. But if media outlets get suckered into helping them, then it isn't GlaxoSmithKline's bad -- it is the journalist's.

With respect to whether RLS is really a disease, I would be inclined to agree with Virginia Postrel:

Why not treat a biological condition you just don't like? (I'm assuming that you are directly or indirectly paying for the treatment.) We don't have to call Restless Leg Syndrome a disease to acknowledge that it disturbs some people's sleep and that those people would like relief. Contrary to what you may have heard, the only sort of character suffering builds is the ability to suffer--a useful ability in a world where suffering is the routine nature of life but not a virtue that makes the world a better place.

If RLS makes people uncomfortable -- and in serious cases it is reported to feel like burning and tingling that you get when your leg falls asleep...hence, yes it does -- does it really matter whether it is a disease or not?

In light of my previous post on cell phones and nausea, I am perfectly willing to explain to someone when I think their issue is all in their head. There are non-diseases out there, fictions created by either individuals or by interested groups. However, if someone persists in spite of that advice in seeking treatment, that makes me concerned and it makes me more likely to explore the matter further.

I feel like in issues of suffering the tie should go to the runner. The burden of evidence is on the practitioner to show that there is nothing wrong rather than on the patient to show that there is something wrong. This is particularly true if the patient is really the one paying. A lot of people participate in medicine that I consider nonsense, but fundamentally they have a right to do what they want with their bodies, my definitions of disease notwithstanding.