The newspapers love a good Health Scare, says Ben Chu. Warning about the hidden dangers lurking in mundane parts of life is a sure way to grab readers’ attention. Last week came reports that Nutella might pose a cancer Risk, as it contains processed palm oil; the week before, we heard that living near a busy road raises your chance of getting dementia by 12%. The problem with these tales isn’t that they’re bogus, it’s that they present legitimate scientific findings in a misleading way. They fail to put dangers in context to make the key distinction between relative and absolute risk. There’s an 11% chance of getting dementia no matter where you live (the absolute risk): and you increase it by a slender 1.32% (i.e. 12% of 11%) if you live near heavy traffic. So what sounds at first like a serious increase in the risk of getting dementia actually means that “of 100 people living near a busy road, around 12 will be afflicted, rather than 11”. The same goes for Nutella: the risk it poses is trifling compared, say, to that posed by smoking. Without proper context, these health scare stories are all but meaningless.
Ben Chu
