How to Live Longer

28 September 2008

Interview with

Nick Wareham, MRC's Epidemiology Unit, Addenbrooke's Hospital

Ben - Professor Nick Wareham joins us now. He's the director of the MRC's Epidemiology Unit at Addenbrooke's Hospital. He's been part of the European Prospective Investigation of Cancer study, better known as EPIC. In January this year they announced there are four simple things you can do to extend your life by an estimated 14 years. Nick, thank you for joining us. What are these four things that people can do and why do they have such a large impact on how long we live?

Nick - They're smoking, drinking in moderation, not being totally sedentary (so having sufficient physical activity) and eating a diet that's rich in fresh fruit and vegetables.

Van GoghBen - I guess when you say smoking you mean not smoking?

Nick - Not smoking, yes! Absolutely.

Ben - Why do they have such a big impact?

Nick - Well, they are risk factors for a whole range of chronic diseases and indeed many of the diseases that you were talking about earlier to Steve: cancer, cardiovascular disease. These are the diseases that really shorten our lives and for which we have evidence that shortening is modifiable. In the study you're referring to this is observational data. It's not an experiment. We haven't had a group of people who we've randomised to be smokers or non-smokers. These are observations in a very big population study but they are robust. Really, what was surprising about the observation was not the fact that smoking and drinking too much are bad for you. It's really the magnitude and it's the scale of the effect on longevity that we observe.

Ben - These are obviously very difficult things to study. You have to rely on people being honest. Obviously if you've got a secret smoker he could squiff your data completely. How do you try and look at all these different lifestyle effects? It's obviously difficult to say these people are healthier - it's easier to say these people lived longer. How do you pull all this data together?

Nick - What you have to do is you collect a very big cohort. A cohort is a population of people who you recruit at baseline. You hope that they're free of disease at that point. You ask them questions or you may monitor different behaviours. Then you wait because the key thing is elapsed time. Over time some people go on to get particular diseases and some people unfortunately die. In the study that we reported earlier this year we started out with a cohort of 25,000 people in Norfolk who'd helped us in the beginning of the 1990s and who were then followed up to see who would get a disease. Really what the essence of epidemiology is that scale, very big studies; and then probability. Whether or not someone goes on to get disease is a process that involves an element of chance. Clearly some people have certain lifestyles and do very well. Some people have the same lifestyle and do very badly but on average one can estimate the probability an event will occur. That's what you do in epidemiology.

Ben - So epidemiology's obviously quite a powerful technique but a lot of people would say based on their personal experience or anecdotal evidence, 'My uncle smoked and drank a bottle of whisky every week and lived to 108.' Are these people taken account of or do you try and go for the common denominator? Are you looking at the average or are you looking at the normal?

Nick - We're looking at everybody. So for everybody who's got an uncle Tom there's probably a equivalent number of people who have an uncle Frank who might have lived and exemplary lifetime in terms of the behaviours we've talked about but was cut short by a disease. One's looking at average probability. Unfortunately most people tend to remember the anecdotes that are an excuse for unfavourable lifestyles.

Ben - One of the things you've been working on is how activity in earlier life affects things like type 2 diabetes or other diseases associated with age. What have you found so far?

Nick - Physical activity is probably a very powerful determinant of many of the diseases that we're seeing rising today. This is clearly a major factor of why as a population we're tending to get more overweight. Overweight by itself is the single biggest determinant of type 2 diabetes. We operate in terms of what's called relative risk in our game. That's comparing the risk of a disorder in one group compared to a comparison group. If you were to take obesity as a risk factor the relative risk of something like 60 for someone who is overweight compared to someone who is normal weight for type 2 diabetes. It's very, very strong. One of the reasons we focus on that is in part because it's an important factor but in part because it's relatively easy to measure. The problem about physical activity is it's incredibly difficult to measure and we rely on self-report. We ask people about their physical activity. The bit of activity that people can remember is that part that usually involves putting on lycra or going to a gym or something very specific and circumscribed like that. In fact what we're finding is that part is important but that part doesn't actually occupy much of our life. Most of us spend most of our energy in a rather insensible way just walking around or standing running and sitting. We've been developing techniques for studying that aspect of activity. It seems that part is really important for determining obesity and diabetes risk. The importance of that is not just as an observation but what it says about what you should do about the problem. Promoting sport and encouraging exercise is absolutely critical. In a population we probably need to also be thinking about whether we just encourage people in an insensible way to waste more energy. That means re-engineering society, putting staircases in more prominent positions, perhaps moving escalators or lifts. Things like that.

Ben - Epidemiology is a good tool for forming policy if you can say these sorts of things. What do you think we should do to try and make our population age more healthily?

Nick - I think we should clearly focus on those four behaviours. There's four critical public health targets and I think we've made progress amongst adults smoking. What's discouraging is the number of children and adolescents who are taking up smoking. If smoking gives rise to hundreds of thousands of deaths per annum unfortunately the smoking has to recruit that number of people just to keep that business stable. I think focussing on the smoking message on people starting is as important a public health issue as trying to help people stop. Clearly there's been a big furore recently about the moderating alcohol consumption and that is something that's going up. There's a public health issue. Fruit and vegetable intake: there are clearly the five-a-day messages and we should stick to those and try and do our best. Physical activity: in our study the risk group was actually totally sedentary. They had a sedentary job and were doing nothing in their everyday lives in terms of leisure time activity.

Ben - Your traditional couch potato?

Nick - Yes. That and I guess the message here is that the public health recommendation which is to do 30 minutes five times a week is a long way from some people's reality. I think there's an alternative message which is actually just do some more because there are benefits to doing something other than nothing.

Ben - Even things like hovering, which I've been told actually burns quite a lot of calories.

Nick - Hoovering, yep. Especially amongst men!

Ben - DIY too.

Nick - DIY, anything you can. Actually DIY is  - we all sit for most of our jobs and there's a very interesting recent study about the time spent sitting and its relationship to diabetes risk. If we've got a sedentary job there's maybe not much we can do about the total duration of sitting. In the same study what they looked at was if you break that sedentary time but overall the sedentary time as a totality is the same, people who had more breaks in the sedentary time, had a lower risk. I think there may be some important messages there about getting up from our desks and our computers periodically. I would argue it's probably good for concentration. It would be very interesting if it was actually also good for our physical health.

Ben - You said that drinking was going up at the moment. Is it likely that we are storing up problems for the next generation? Are today's adolescents going to be even more disease-prone than today's pensioners?

Nick - That is the six million dollar question. This is really the problem that we face in public health. We always used the past to predict the future. The cohorts that we have now, on which we're basing our information about risk, studies like EPIC, those studies recruited people maybe 20-30 years ago when the risk factors were as they were then and medical care was different. The issue is what are the current generation going to face in the future? We don't know. All we can do is say we know that obesity and other risk factors are incredibly important. Based on our observations from the past we would say that the current generation, if they don't take some action, are going to have problems with their metabolic health in particular.

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