Dodgy data bad for your public health

Mark Short, Manager of the Australian Cancer Database at the AIHW confirmed his organisation was the source of the figures, but added:

"However, there are some important 'ifs and buts' that go along with it which perhaps the ABC programme did not explain. I'm only going to explain the main one to you because the others would be getting into too much nitty-gritty detail.

"Risk of being diagnosed with cancer by age 85 (1 in 2) does NOT (his emphasis) equate to proportion of people 85 and over who have had a diagnosis of cancer. If that were so, as you point out, half of all people 85+ would have had a diagnosis of cancer (before reaching 85), which is clearly not true.

"What the risk figure is saying is, based on the cancer incidence rate statistics we have right now and assuming that they remain the same into the future, a baby born today has about a 1 in 2 chance of being diagnosed with cancer before they turn 85.

"If that person gets cancer they have a fair chance of dying from it before they turn 85 in which case they disappear from the population (or, just to make matters more complicated, they might never be diagnosed with cancer but still die before turning 85).

"So the people who make it to age 85 are not representative of all the people born 85 years ago; they are the lucky ones, at least as far as longevity goes.

"If you imagine that everyone who dies remains in the population as a zombie (a non-hostile one!), then perhaps about 1 in 2 members of this 'alive + zombie' population will have been diagnosed with cancer before turning 85.

"I say 'perhaps' because, as mentioned in the first paragraph, there are other ifs and buts that go with the mathematical formula that calculates the risk; the risk figure should be taken as approximate rather than exact."

From all this hedging it's clear that the ABC's original statement is at best open to misinterpretation and most certainly depressingly alarmist.

The Australian Bureau of Statistics publishes clearer figures gleaned from the census: 'In 2011-12 there were 326,600 persons who had cancer, or around 1.5 per cent of the Australian population. This reflects little change from 2007-08.'

The real concern that should have drawn the ABC's attention is this: Despite all the advances in preventative measures, sophisticated treatments, social awareness programmes, massive expenditure and intensive world-wide research the risk of getting cancer has remained the same for the past 29 years. Why?

Whatever that risk it certainly doesn't mean that 'if you don't get it, the person sitting next to you will.' Unless that person is an octogenarian statistics juggler. Or a zombie.