Every morning seems to bring news of a new medical danger. Some health scares fizzle fast, but others look like they will never run out of fuel. How can we make sense of them without turning into quivering neurotics?
With baby boomers pushing 70, dementia scares are becoming more common. Take recent warnings about mercury in fish. People are eating more fish to ward off heart disease. But could mercury trigger brain changes that lead to dementia? To check it out, researchers at Rush University Medical Centre in Chicago studied the brain tissue of deceased elderly people to look for a link between mercury levels and brain plaques, a sign of Alzheimer’s disease. The good news: they found no link. Even better, a paper in the Journal of the American Medical Association in February 2016 showed eating fish reduced brain plaques in people whose ApoE4 gene put them at high risk.
Another dementia scare grabbed headlines in February, when German researchers found a link to commonly prescribed heartburn medications. The drugs are called proton pump inhibitors, or PPIs. (Their generic names end in prazole – omeprazole and esomeprazole are two examples.) At first glance, the results look disturbing. But, as with any scare, level-headed questions need to be answered before people with heartburn succumb to panic. First, does it make biological sense that PPIs could cause dementia? Maybe. But there should be a dose-response effect: the higher the
dose or the longer a person takes the drugs, the more likely the onset of dementia. No one has shown that is the case. There are also alternative explanations for the link. For example, people who have heartburn and take PPIs tend to be older, fatter and are more likely to smoke than people who don’t take these drugs. Those factors may put them at risk of dementia – not the drugs themselves.
The case demonstrates the classic danger of assuming that events that are correlated – taking PPIs and developing dementia – are causally related. Other health scares flourish when there is not even a clear correlation. For example, take the fears of a link between mobile phones and brain cancer. That radiation emitted from phones could be zapping our brains sounds plausible. But the story fizzles out when you examine the evidence. We know the dates when mobile phones came on the market and have ample data on usage patterns. If phones raise brain cancer rates, there’s been enough time for the dial to have shifted. It hasn’t. Reviews of studies looking for a link between mobile phones and brain tumours also show different results depending on the methodologies used. So the science is inconsistent. There is no basis to even start to assess a dose effect. These days people are more likely to be texting, taking photos or using ear buds than clutching their phones to their heads, further complicating the data. Another question is whether it is biologically plausible for mobile phones to cause cellular damage: in contrast to X-rays, the wavelengths mobile phones emit are too weak to trigger cancer.
My point here? It’s not that we should ignore the possible risks of mercury pollution, overuse of PPIs or mobile phones. But these cases demonstrate how people can bark up the wrong tree. Why worry about unproven scenarios that might, at best, account for tiny risks, when the greatest proven risks are obesity, alcohol and being a couch potato – which are all preventable.
Research by psychologists such as Nobel laureate Daniel Kahneman and his late colleague Amos Tversky suggests that we happily swim in a sea of risk – for instance we seldom think twice about getting into a car despite the staggering number of injuries and deaths they cause. Yet for many folks, flying sends the fear barometer off-scale though it’s a far safer way to travel. Our emotional response tends to be heightened if we feel we have no control over our exposure, or if a giant conglomerate profits from the activity.
We will never be rid of scares. Nor should we, because sometimes they do uncover a real threat. But as Kahneman suggests in his book Thinking, Fast and Slow, we need to slow down and consider what matters more rationally.