Understanding Risk

One of the most difficult things about understanding health reporting in the popular media is making sense of the risks associated with various dietery choices or behavioral habits. Unfortunately the reporting on this tends to be quite bad. This page collects some articles that put such risks into perspective.

Medical Risk

Understanding risk related to medical practices

Risks associated with Alchohol

A Link Between Alcohol and Cancer? It’s Not Nearly as Scary as It Seems

• Depending where you look, you can find evidence that says that nearly everything we eat is both associated with higher rates of cancer and lower rates of cancer.
• In the United States, the announcement also notes, 3.5 percent of cancer deaths are attributable to alcohol… Of course, this means that 96.5 percent of cancer deaths are not attributable to alcohol. If we eliminate heavy drinking, which no one endorses as healthy and where the association is surest, that number climbs. If we also eliminate those who smoke — smoking is believed to intensify the relationship between alcohol and cancer — the number of cancer deaths not attributable to alcohol approaches 100 percent.
• Relative risk refers to the percentage change in one’s absolute (overall) risk as a result of some change in behavior. (And 1.04 is a 4 percent change from 1.0, which represents a baseline of no difference in risk between an experimental group and a control group.)
• A 40-year-old woman has an absolute risk of 1.45 percent of developing breast cancer in the next 10 years. This announcement would argue that if she’s a light drinker, that risk would become 1.51 percent. This is an absolute risk increase of 0.06 percent. Using what’s known as the Number Needed to Harm, this could be interpreted such that if 1,667 40-year-old women became light drinkers, one additional person might develop breast cancer. The other 1,666 would see no difference.
• Randomized controlled trials of alcohol (they do exist) show that light to moderate drinking can lead to a reduction in risk factors for heart disease, diabetes and stroke. These protective factors may be greater than all the other negative risk factors (even cancer) that might be associated with light or moderate drinking. More women die in the United States of heart disease than cancer. So do more men.

The risks of alcohol (again). A recent paper published by the Lancet…

• Let’s consider one drink a day (10g, 1.25 UK units) compared to none, for which the authors estimated an extra 4 (918–914) in 100,000 people would experience a (serious) alcohol-related condition. - That means, to experience one extra problem, 25,000 people need to drink 10g alcohol a day for a year, that’s 3,650g a year each.
• To put this in perspective, a standard 70cl bottle of gin contains 224 g of alcohol, so 3,650g a year is equivalent to around 16 bottles of gin per person. That’s a total of 400,000 bottles of gin among 25,000 people, being associated with one extra health problem. Which indicates a rather low level of harm in these occasional drinkers.
• But claiming there is no ‘safe’ level does not seem an argument for abstention. There is no safe level of driving, but government do not recommend that people avoid driving.
• Come to think of it, there is no safe level of living, but nobody would recommend abstention.
• Presumably people who choose to drink alcohol moderately get some pleasure from it, and any risk needs to be traded off against this enjoyment.

Risks associated with Coffee

Coffee and cancer: what Starbucks might have argued

• Assuming, very pessimistically, that cancer shortens your life expectancy by 20 years, then the 1 in 300,000 chance that the acrylamide in that daily cup will give you cancer works out at a lowered life expectancy of 0.0008 months, or a total of half an hour lost on average due to a lifetime’s consumption. When it comes to the benefits, extensive evidence exists that routinely drinking coffee improves overall health, with a massive recent review concluding that ‘high versus low consumption was associated with an 18% lower risk of incident cancer’. The data from a study of over 500,000 people suggests that a habit of a daily cup is associated with around 3 months increased life expectancy for men, and around 1 month in women. Therefore the benefits of coffee may outweigh the acrylamide risks by a factor of at least 1/0.0008 = 1,250, or say a thousand, an extraordinary benefit/harm ratio.