Tuesday, September 4, 2018

What's causing the cataract epidemic?

Strangely, we seem to be in the midst of a cataract epidemic!  It seems that everyone I know is having to have their lenses replaced, and I have been experiencing glare and other issues that suggest the same may be looming for me.

It is the personal experience that drew my attention to this epidemic.  That is, I have seen no stories about this in Science or the public news media.  That is very strange, since they seem to seize upon any even marginally interesting story.  Yet this epidemic has not hit the headlines, at least not yet.

So what could be causing it?  This is far, far from my area expertise, so I can only speculate in very generic terms. What has changed that might have epidemic consequences?  Here are a list of candidate factors that may have changed recently enough to be responsible (but I confess it is just a guess-list):

(1) Is it food?  With processed and GMO animal and plant foods increasing their prevalence, widely and recently, as well as pollution of the seas from which seafoods come, an obvious suspect would be dietary.  Junk foods and other such habits could have effects that are subtle but accumulate, with delayed-onset vision consequences.  Dietary factors clearly are, after all, responsible for many 'modern' diseases. 
(2) Is it viral or infectious?  So many of us move around the country and, indeed, the world that any virus arising even in a remote part of the globe can rapidly spread.  Air transport from tropical to temperate zones would be a major suspect, as would international transport of goods and so on.  But what virus or infectious agent might be involved is unclear, nor do we know where a similar epidemic might be occurring, unreported. 
(3) Is it recent environmental contamination, in air or water?  It is impossible to ignore global air and water pollution as potential cataract causing factors--even if the mechanism itself is not known.  After all, has it even been examined, given that the epidemic hasn't yet really been recognized?  Air and water currents circulate widely around the world, which could make the causal source of the epidemic very distant from the consequences.  It might not even be suspected.  After all, the lens is a very special kind of tissue and a connection may be very strange relative to what the usual exposure-consequence studies look for, not to mention the statistical methods used which could be quite inapt. 
(4) Or, being very cynical, could it be marketing or profiteering by the companies that make the gear and supplies that are involved?  In that case, perhaps the idea that there is a real epidemic may be mistake--we would just be being told that there was.  This subjective, cultural sort of factor would be vary difficult to document.  After all, gear-makers do need to make sales of their gear.
Overall, I am stunned at what seems to me to be an obvious but almost wholly unreported yet major epidemic that seriously threatens quality of life.  As I must acknowledge in what is a speculative blog post, the whole story could be my ignorance of the literature.  I am a geneticist, but I have seen no reason to think this could be genetic, since our population's genotypes have not changed in any substantial way in the recent decade or so.  But if not genetics, then what?  One must at least ask that question!  Yet, strangely I think, the professional epidemiological literature seems to have ignored or even been unaware of the major epidemic, which from my point of view seems clear to me; such neglect is very hard to understand, since (again, to be rather cynical) epidemiologists are naturally eager for any Big Problem they can find to justify Big Studies.

This blog site is usually about genetic causation and its associated scientific issues, but once the question of the seeming neglect of a cataract epidemic struck me, I decided I should at least use Mermaid's Tale to air it.  I would welcome any comments that raised original or even partly plausible explanations.

However, and finally, I must end by acknowledging that I have done no rigorous study of the cataract problem.  Indeed, at my age, I should long ago have learned to avoid the temptation to talk to so many of my peers about it.  It could frighten them.  Before suggesting that it is a major epidemic, I should think about who I'm talking to.


Ken Weiss said...

Well, this post has turned out to be better--or worse!--than I had expected. At least one reader thought it showed that I was losing my marbles. That may be so, but that's irrelevant. This was supposed to be a spoof post, with an implied lesson. It has to do with simplified claims of association and causation, and ignoring or not using relevant variables. In this case, the implication that there is a cataract epidemic was based on my only talking to people who are older. Older people do experience more cataracts, and since we have an aging population, there are more cases (and support for the remediation industry, as noted). But there is no evidence (that I know of) that once you take age into account, that cataracts are becoming more common.

But it is oh, so easy to ignore relevant variables or to jump to some dramatic story. We see this almost daily in the genomics claims literature. In the case of this post, if you just take age into account, and sample properly across the age distribution, you would have no reason to expect there to be an 'epidemic' in the usual connotation of the term. At least, if there is, and it is more than just the deterioration of lens molecules, I know of no such evidence. I haven't studied the problem myself, but it seems only to be affecting old people, as a part of aging. One might say there is an 'epidemic' of old-age, of course.

In this spoof, it was a sampling issue: I had apparently only considered my age peers who, indeed, are experiencing an increasing risk of cataracts. But there is no evidence or reason I know of to suspect evidence of an epidemiological nature--that is, lifestyle-related causes that are becoming more common, and hence causing an epidemic. There is no reason that elderly people in the past had lower risks of cataracts. If there was, and it wasn't just a diagnosis issue, then we might, indeed, have something to ask about.

If there were such an 'epidemic', it could be due to many legitimate 'causes'. But the most likely would be indirect associations: Antibiotics and advancing effectiveness of medicines and surgery, reduction in smoking, improved diets, and so on could be view as 'causing' cataracts--simply by enabling people to live longer. That is, of course, a different kind of 'cause', even if the association with age is entirely real. Better diagnosis and the commercialization of cataract replacement technology mentioned in the post, could also increase the reporting or diagnosing of cataracts, whereas in the past people may have just lived with it. The prevalence per se may have changed only in the sense of an increased prevalence of older people with the resources to have something done about deteriorating vision (e.g., to keep seeing the optometrist), and my post simply reflecting a careless sampling only of old people. I have no reason to think that the age-specific prevalence of cataracts per se has changed at all. But if one is looking for a story that looks plausible, it is so easy to construct one.....

I had thought this spoof would be more transparent than it apparently was (that is, rather than as a manifestation of my senility). But my point would be to ask: How much of the rush to publicity, and the lobbying for large grants and so on, the careerism that has taken hold of science these days, leads investigators to make claims about causality that are in various ways too hasty, naive, or incompletely considered, because we are not trained to think more carefully, or claim more carefully, or take more time to assess a problem more carefully before rushing to conclusions?

So, this post was a spoof, but with a serious point to try to make. Whether I am as senile as its nonsense may suggest, is an entirely different question that I care not to investigate.....

Ken Weiss said...

I had better add another comment.

A web-scan of the literature suggests that some authors have indeed attempted to find lifestyle factors that affect the risk of cataracts. That of course is no surprise, but it is a bit more surprising that I found nothing very recent, and the papers I did find seemed to identify the usual lifestyle culprits (smoking, etc.). Their association in statistical epidemiological studies doesn't of course prove actual causation, since so many lifestyle variables are correlated and may not be measure or even identified. In any case, I have no judgment to make on the existing reports, except that for a trait so common, the literature does seem scant and one can ask how trustworthy it is. One can also say that just attributing increased cataract prevalence to 'aging' and offering some molecular speculation about lens molecules deteriorating isn't very helpful. But it may be that that is mainly what there is! Anyway, I think it doesn't really vitiate the point I intended in writing the post.....

Anonymous said...

I didn't recognize the spoof at first, either :( Maybe the problem is that cataract is not so widespread. Given my own age range, presbyopia would have been a more obvious case.
Thanks for the lesso, anyway.M.