The Problem With Smoking Epidemiology

Some of you may remember the CATCH debate over at Frank Davis' blog, primarily between myself, Frank and Chris Snowdon about the effects of active smoking on health. Frank made a very interesting point that, so far as I can see, hasn't been acknowledged in any of the studies: cigarette size.

Frank stated that true science uses rigorous standards of measurements, and to keep it as basic as possible when we say "one centimetre" we don't mean "somewhere between this length and that length, but it varies" - one centimetre is one centimetre, and the recent success in trapping antimatter was certainly only achieved with rigorous and painstaking accuracy, not a "it should be sort of that much". In mathematics, 1+1 = 2, 1.5 + 1 = 2.5; the slightest change makes a big difference to the outcome, and the same is true of science.

Epidemiology, particularly on smoking, is somewhat different. The humble cigarette is itself considered a unit of measurement - "how many cigarettes do you smoke a day?" for instance. This is fine if each study participant smoked the same brand, for they will be the same size and strength. However, beyond such a level of control there really is no symmetry. A marlboro Red is different to a Marlboro Light or a Camel Light, but it gets murkier in the world of roll your own.

Typically, a 'rollie' is much smaller than the size of a standard pre-made cigarette. Yet in studies the researchers do not ask if the participant smokes pre-made or roll-ups, rather if both smoke ten a day, they get classified as ten a day - when in reality the one rolling his own is smoking perhaps 50% that of the person smoking the pre-mades. But some people roll their cigarettes incredibly thin and tight, with or without filters, while others roll them as fat as a regular cigarette. Others use the 'tubes' to make their own cigarette that is the same size as a pre-made.

On my current trip to America I have noticed the huge difference in filter size for roll-ups compared to what we have in the UK. At home, even the largest filter commonly available is about half the size of that found in a pre-made cigarette. In the USA, filters are almost the same size as the pre-made filters, or they can be smaller, and the papers are much bigger too. Some filters are longer and narrower, others wider and shorter. The paper tends to be much wider than what is on sale in the UK, so roll-ups in the USA can be much bigger.

Studies into smoking have tried over the decades to turn a 'cigarette' into a unit of measurement. The problem is, it isn't. It's like asking how many plates of food someone eats a day when the plate could range from a saucer-sized one to a large dinner plate. Hence why typically diet research deals in calories, and drink research deals in units. With cigarettes, such a rigorous distinction has not been made. Not only do cigarettes vary a lot, but people have different smoking habits - some will smoke only half, some will smoke while preoccupied and inhale very little, some will inhale every available puff that's on offer.

If we try to evaluate something scientifically, we need protocolos, measurements and definitions. If we don't have them and try to measure something anyway, what can we really deduce? Even if we happen to find some sort of link, there's no way to of testing the authenticity of the results.

For much more interesting musings over this topic, head over to Frank's blog.