Delaying the Inevitable

Why is it that newspapers often give completely contradictory health advice? It’s difficult enough to keep track of what is supposed to be healthy, without the papers changing their minds the whole time.  Let’s just look at the Daily Mail for example, a paper that hands out health advice more freely than a Jehovah’s witness hands out pamphlets. A brief look through the Daily Mail health pages tells you “Aspirin causes cancer” but also “Aspirin prevents cancer” . “Beer causes cancer” except when “Beer prevents cancer” . “Coffee causes cancer” but also “Coffee prevents cancer”. “Eggs cause cancer” apart from the times when “Eggs prevent cancer”. “Soya causes cancer” but also “Soya prevents cancer” . “Stress causes cancer”   but sometimes “Stress prevents cancer”. See a trend here? Well, part of the reason for this is that knowledge about a subject changes over time. We all remember adverts where doctors recommended cigarettes , but you’d struggle to find ...

Running tests to diagnose diseases should be easy right? Let’s say you take a blood test – if the result is above a certain threshold, you’ve got the disease. Easy. Well, unfortunately it’s often more difficult than that, read on to find out why. Blood tests, like any thing else in a population, have a range of normal values. Imagine they’re a bit like height. If you plot height of people on a graph, it would look like a “Bell-shaped curve” with a lot of people with heights around the average, and fewer people very tall or very short. This is called a “normal distribution” . It’s the same with blood tests. Blood tests have a “normal range”, with most people having values around the average, and fewer at the extremes of higher and lower values. Let’s say we’re looking at a disease like hyperthyroidism (an overactive thyroid). You could work out a cutoff value (the dotted line in the picture below), which anyone with hyperthyroidism has a blood test above, and anyone without hyperthy...