Thursday, 21 July 2011

The overtallness epidemic

[trigger warning: body issues]

Researchers have announced that (BBC) being overtall gives an increased risk of cancer.

I haven't looked at the study itself, so I can't comment on whether it was well-conducted or not. I'm just interested in how the reporting has gone, so I'll assume it was well designed.

Essentially the study has found that an increase in height in women from around 150cm to around 170cm was associated with an increase in the cancer rate from 0.75% a year to 1% a year. Not a large effect for individuals, but certainly a noticeable one at the population level.

They also carried out a meta-study that suggested that a similar effect existed in men, though the BBC article goes into less detail about this.

There's a suggestion that this effect is in part behind the rise in cancer prevalence, since average height has risen by about 1cm every decade in Europe.

Cue panic and press articles about how the so-called "overtallness" epidemic is ruining our health, and we're all going to die if we don't wear heavy shoulder pads to shrink ourselves back down to 19th Century levels, all illustrated with photos of headless tall people.

No? My mistake.

The BBC article is actually calm and measured on this topic. It points out that there's no known mechanism by which overtallness could affect cancer prevalence, though a couple of theories are suggested. It doesn't blame tall people for bringing it upon themselves or suggest that they need to do more to reduce their height1. Nor does it ignore the structural issues that make it hard for people to avoid being tall, pointing to better childhood nutrition and fewer diseases as reasons for overtallness.

One of the theories even suggests that overtallness doesn't cause cancer at all, but is merely a marker for underlying conditions that cause both overtallness and cancer. Correlation is not causation, after all.

If every medical research sub-discipline was so cautious about claiming causative relationships between health conditions and physical attributes, and similarly restrained about suggesting drastic individual measures to change the physical attributes, then we might have considerably better public health policy.


1 As I've said before (almost), there is no known safe way to permanently reduce height, though there are several methods which will appear to give noticeable effects if the follow-up period of the study is - no pun intended - too short, There are also some surgical methods that appear somewhat more effective but have extremely dubious safety records and large side effects.