Can watching TV make you die younger?
Beware any headline in a newspaper or blog that starts with a question.
Generally the answer to the question is no, and is a means for the writer to grab the reader's attention and then proceed to irritate them. I will try not to by giving my conclusion straight off - no, watching TV will not make you die younger.
I pose the question because of a study that may well get some media attention. Published online in the British Journal of Sports Medicine it suggests that compared to people who watch no TV, those who spend a lifetime average of watching six hours a day can expect to live nearly five years less.
The average Briton watches three hours TV a day so you might think you are in the clear. But according to the research from the University of Queensland, any TV watching may shorten your life.
The author of the research paper Dr Lennert Veerman, from the Centre for Burden of Disease and Cost Effectiveness, told me they had adjusted their research to exclude people who were physically active while watching TV - such as running on a treadmill or rowing.
As someone who works in television I told him I was worried I might be slowly killing off my viewers. I was even more worried by the paper's conclusions that "TV viewing may have adverse health consequences that rival those of lack of physical activity, obesity and smoking; every single hour of TV viewed may shorten life by as much as 22 min."
War and Peace
We all surely know that smoking is really very, very bad for us. But this research suggests that watching TV may be on a par. Indeed it even suggests that for those over 25, half an hour of TV viewing "may shorten life to a similar degree" as smoking a cigarette.
One obvious danger here is that smokers will say their habit is no worse than TV, so they might as well carry on.
So what about those people who don't watch any, or not very much TV? Presumably quite a few of them spend time reading books. Sitting reading is a sedentary occupation, and yet no-one is suggesting you should avoid "War and Peace" or the later, over-long Harry Potter novels.
I put this to Dr Veerman who agreed it may not be the TV viewing itself that was cutting life expectancy: "It is always possible that the effects are associated with lifestyle rather than the TV viewing itself" said Dr Veerman.
Which means that people who watch a lot of TV tend to lead unhealthy, sedentary lifestyles. It's not the six hours of TV which is killing them, but the likelihood that they are not filling the rest of their waking hours with healthy physical activity. Those who watch huge amounts of TV are also probably more likely to have an unhealthy diet and be overweight.
Have you noticed how many umbrellas are used when it's raining? So umbrella use is associated with wet weather, but common sense tells us umbrellas don't cause rainfall. It's common sense of course but science and statistics can too easily be taken out of context and divorced from reality.
Earlier this year an American study found that more than two hours of TV viewing per day significantly increased the risk of type-2 diabetes and cardiovascular disease, and more than three hours of daily viewing increased the risk of premature death.
That paper made it clear that it was not watching TV for long periods that was unhealthy, but it reflected an unhealthy lifestyle.
Dr Veerman said his latest study is meant to have a positive message, that every step counts. In other words, small alterations in lifestyle - like watching less TV and doing something active - can bring about significant health benefits.
That point is underlined in another new study on physical activity, from researchers in Taiwan. In the Lancet online, they suggest that 15 minutes of physical activity per day can reduce a person's risk of death by 14% and increase life expectancy by three years compared with inactive people.
The researchers analysed the medical screening results of more than 400,000 Taiwanese people with an average follow-up of eight years. They found that every additional 15 minutes of daily exercise beyond 15 minutes a day further reduced mortality by 4%.
Last month the Department of Health updated its advice on weekly physical activity. It recommends 150 minutes a week, and "reducing and minimising periods of sedentary behaviour". Even if you don't manage 150 minutes exercise a week but do around 90 minutes, you could still get significant benefits.
The Taiwanese and the Australian research both point in the same direction - that physical activity is good for you and even small changes in lifestyle could help us lead longer and healthier lives.
I won't be giving up television, or long novels, but I might try to snack less and walk more.