Royal College of Physicians and their dodgy stats on Passive Smoking

First things first - I am sure that smoking is bad for the smokers health and I have no doubt that tobacco companies conspired against the public to hide this information in the past. I am also sure that everyone in the UK knows that smoking is bad for the smokers health.

However, a while back I was intrigued by the figure of 17,000 under 5s needing to be admitted to hospital each year as a result of passive smoking their parents smoke. This figure crops up everywhere and seems to be the basis of all arguments against individuals smoking in presence of others (whether adult or child). http://www.google.co.uk/search?q=17000+under+5+hospital+smoke

I traced this figure back to 'Smoking and the Young' a Royal College of Physicians publication where the figure is calculated, and then started disecting it. At which point it pretty much falls apart.

1) It uses for admissions figures from the 1970 cohort survey (published as a book 'From Birth To Five') to calculate the percentage of admissions that it attributes to passive smoking.

- The survey did not register the reason a child was admitted to hospital (i.e. whether it was potentially smoke inhalation related or not (say a broken arm or cigarette burn!)) only whether the admitted child's mother smoked.

- The survey qualifies is figures stating "it would be dangerous to interpret information on hospital admissions as an index of ill health in the population, they are presented here merely as events that occurred in a population of children". This qualification given on the basis that admission of children to hospital could often made on social reasons (ie maybe whether the mother had other children or worked etc so may have difficulty caring for a child at home) rather than a pressing medical requirement for hospitalisation.

- The survey only registered whether a mother smoked when the child was aged 5, not whether they had smoked while the child had been growing up, nor whether they had a partner who smoked.

2) It uses the 'General Household Survey 1988' to estimate the total number of under 5's admitted to hospital in a year.

- This surveyed only 1400 children aged 0-4 of which around 25 had a hospital admission in that year (for all reasons). This Royal College of Physicians have extrapolated this to estimate for a population of 3.4 million(!).

So from this very shaky base, of children of mothers who smoked on their 5th birthday who were admitted to hospital for any reason in a year, using data in a way that it was specifically not intended for, then extrapolated over several orders of magnitude. We get headlines declaring that 17,000 children are admitted to hospital with breathing complaints brought on by passive breathing their parents smoke.

There may be evidence of damage caused by passive smoking - but if there is, then this isn't it.

I hope these kind of jokers aren't let anywhere data on (say) global temperatures... they will probably claim the earth is freezing away or boiling away or something and insist that they get evern *more* of our money to 'do something about it'...

** Edit 18th Sept 2013 **

There is a more recent report
http://www.rcplondon.ac.uk/sites/default/files/documents/passive-smoking-and-children.pdf
Its stats seem to be merger of many other studies - each of which could be as poor as that set out above(!) - but even this puts the hospital admission figure at 9,500 for all under 16. Almost half the number for a group three times the size compared to the original information... So while the figures are unreliable, it certainly confirms that the Royal College of Physicians cannot be trusted to produce reliable statistics.