TV shortens life, exercise lengthens it – but what if you mix’n’match?

Bad for your health? <em>Picture: Evert F Baumgardner</em>
Bad for your health? Picture: Evert F Baumgardner
Apparently watching six hours of television per day can shorten your life by five years. Researchers in Australia have come up with this finding – and warn that watching too much TV could be a public health hazard on a par with smoking and being obese.

Indeed, they go further than this and, writing in the British Journal of Sports Medicine, point out that if one cigarette cuts life expectancy by 11 minutes, watching half an hour’s telly can be just as bad.

A fix of Lambert & Butler or EastEnders? It’s a tough one, but it seems both are going to kill you.

There is hope, however. Some other researchers – this time in Taiwan and writing in the über-respected Lancet – say that just 15 minutes of physical activity per day reduces a person’s risk of death by 14 per cent and increases life expectancy by three years, compared with inactive people. Each further 15 minutes of exercise reduced mortality from all causes by a further 4 per cent.

Like the Australians, the Taiwanese researchers also draw comparisons with smoking. “In Taiwan, if inactive individuals engage in low-volume daily exercise, one in six all-cause deaths could be postponed – mortality reductions of similar magnitude have been estimated for a successful tobacco control programme in the general population.”

Since reading the press releases for both these studies – they arrived on the same day for publication at roughly the same time – my brain has been in a bit of a mathematical spin. Never very reliable with figures, I’ve been trying to do the sums to see if one would balance out the other.

In other words, if I spent six hours watching telly (therefore chopping five years off my life) but then did 15 minutes exercise, would that mean a net loss of two years? And if I upped the exercise sufficiently, would that mean that I could negate the life-sapping properties of too much TV in their entirety?

And surely the two would be connected. Leaving aside how anyone could actually spend six hours a day watching television (no, not being snobbish here – just finding it hard to think about when you’d fit it in), it tends to involve sitting down. So could you cancel the effect of watching The Hour, say, by doing so while clocking up the miles on a treadmill?

That got me thinking about other ways to increase – or decrease – a normal lifespan, so I turned to Google. Putting in the words “may help you live longer” got a stonking 172 million hits in 0.15 seconds. From news sources of varying reliability, I learn that having supportive colleagues, getting good grades, owning a pet, eating a high-fibre diet, calorie restriction and regular shopping (oh dear, I think I wrote that one up) appear to improve longevity.

That’s just the first page of about a gadzillion; scrolling further suggests – controversially – that worrying might help you live longer, but this is quickly counterbalanced by another study saying that meditation and relaxation is the way to go for a longer life.

Cheeringly, drinking red wine and having a big bottom may also help you live longer, according to other studies (the former reported in the Daily Telegraph and the latter referring to a study from Oxford, therefore they must be true).

Just for balance, I then tried to find stories about things that shorten life (using the less than catchy search term “shorten life expectancy”). Air pollution, childhood obesity, serious mental illness, “excess body fats in older adults” were all among the top results of around 111 million returned within the obligatory 0.15 seconds.

Diabetes, medicine for insomnia or anxiety and being underweight were also among the far from joyful suggestions.

Just for fun, I then searched on “Daily Mail shorten life” and got an astonishing 285 million results – with the factors including having a toyboy (thanks, Bel Mooney), being overweight, yo-yo dieting and binge eating, taking vitamins and the “heartache from losing a loved one”.

For even more hilarity (yes, my life is that exciting), I decided to look at a particular substance on which researchers have differing views: coffee. In the Daily Mail alone, I found out that abstaining from drinking filter coffee can cut the risk of heart disease by 15 per cent. This contrasts, however, with a Mail article from five months earlier which suggests that a coffee a day may cut stroke risk by 25 per cent.

So who do we believe? Sample size, the institution in which the researchers are based, and the journal in which the results are printed all have an impact on how much you can rely on research.

Actually looking at the papers on which the headlines are based is a help; handily enough, many journals – including those owned by the BMJ group – make their contents freely available online.

That shows us, for example, that the Australian research on telly killing you (I paraphrase – irresponsibly, I know) is based on analysis of data in a respected national survey (the Australian Diabetes, Obesity and Lifestyle Study), which involves more than 11,000 adults. The authors constructed a risk framework for the Australian population based on the answers the participants had given when asked about the time they spent watching TV or videos. From this, they estimated that every single hour of TV watched after the age of 25 shortened the viewer’s life expectancy by just under 22 minutes.

Importantly, the authors do not claim to be making a causal link – their work does not say it is watching the box per se that kills you – but they suggest that if further work uncovers a causal link then “TV viewing is a public health problem comparable in size to established behavioural risk factors [eg smoking, obesity]”.

The Lancet paper is also based on a reassuringly large sample size – 400,000 Taiwanese people – and, like the Australian study, is in a respected, peer-reviewed (so called “high-impact”) journal. Again, it has credibility and, importantly, the authors in such journals all have to declare any funding or other sources of possible conflict of interest.

Other studies – often published in journals you’ve never heard of and based on single or three-figure sample sizes – deserve to be treated with more scepticism, especially if the authors are funded by the interest group whose product comes out well in the “research”.

How people get scientific and other information was the subject of a recent investigation by Westminster’s Science and Technology Committee. The report concludes that although the current system of “peer review” (where papers are published only after they have been “passed” by experts in the field) has grown up in a “haphazard and piecemeal manner” and should be reformed, it is still of some value.

The committee recommends creation of an independent regulator to ensure research integrity – basically making sure that research which is published is robust and ethical and that we lay people can rely on it.

So where does that leave us with how to report on the two papers published today? Surely there’s only one possible message: if you want to live long enough to know if Chris (the wife-beating builder in Coronation Street) is going to die from his brain tumour, then stop watching so much telly.

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