Within the UK the Organisation of National Statistics (ONS) has come up with figures suggesting that ⅓ of girls and ¼ of boys born this year will live to see their 100th birthday1. This would occur in the year 2111 of course.
Given that figures provided by the ONS get used in the formulation of Government policies on pensions and healthcare, it is important that they get them as accurate as possible. Unfortunately, when I see BBC headlines suggesting ever increasing lifespans I laugh. The reason? Because in my view they are very misleading.
The main problem for life expectancy projections is that they are based on the past pattern of changes in life expectancy. In the past big increases in lifespan in the UK occured with the reduction in infectious diseases due to drugs and vaccines developed in the last 120 years; the improvements in nutrition as different types of foods became available to all and reductions in smoking rates. However we have in all likelihood by now used up all our trump cards for longevity and now there are just clouds on the horizon.
Clouds on the horizon.
There are a number of reasons that I seriously doubt the projections.
- The obesity epidemic.
- Lack of healthy nutrition.
- Lack of exercise.
- Human Physiology.
- Overpopulation and climate change.
1. The obesity epidemic.
One major factor that gets overlooked is the increasing incidence of obesity in the population. While most people dying today in the UK have not been obese in their lifetimes in the future this will not be the case. Compare somebody dying at age 80 this year, born in 1931 with somebody born this year.
In 1931 the rate of adult obesity was below 1% in the UK. While now it is over 24% and rising. Today’s 80 year old lived most of their life at normal weight. Nowadays most people who reach obese weight carry on growing. What is the likelihood that the 35-40% of kids destined to be obese adults and born today will reach age 80 in any sort of health, or even reach it at all?
Well I thought I'd better check this out for you and I found a large analysis of 57 studies on just this topic in the medical journal, the Lancet2. Taking some of the results from graphs within the analysis we can see that for a men living in modern day western europe and north america, of those with a BMI of:
- BMI = 24 --- 77% will live to 70, 50% to 80 and 15% to 90
- BMI = 32 --- 69% will live to 70, 39% to 80 and 8% to 90
- BMI = 43 --- 49% will live to 70, 18% to 80 and 1% to 90
One thing is clear from the results above, a large proportion of the kids born today will not reach 90, let alone 100. That is because unless the obesity epidemic is stopped by global famine or universal equality of wealth (what else could stop it?), then probably about 40% of adults will be BMI 32 or more in the 2nd half of the 21st century. There will therefore be less than 10% of this group in the running for reaching 100, 10 years before their century year. The ONS won't have factored in the obesity related mortality results into their calculations as it is the convention in life expectancy calculations to discount future changes in technology, environmental change, population genetics etc etc.
** A quick note on obesity.
BMI is conventionally calculated from tables dividing weight by height2. If you use kg and metres then a figure of 30 makes you obese. When taken over the whole population, the increase in average BMI is a suitable measure for the levels of excess fat in the population as a whole. However this classification is not suitable for everyone. A heavily built, muscular man can be in perfect health and have a BMI of 30. Equally a skinny model can be unhealthy in an “obese” sort of way, with a BMI of less than 20 if she has no muscle mass. So if your BMI is 32, you exercise regularly, have a reasonable amount of muscle and a heavyish frame then you don't neccessary need to worry.
2. Lack of healthy nutrition.
Ignoring for the moment the issue of weight, it is also true that you can have your life shortened by what you eat without gaining so much as a pound. This is because you are what you eat and the foods you eat all have particular effects on the body. Eat nothing but bread and sugar all day for 30 years and you are very likely to have type 2 diabetes. You would probably fall prey to more illness with too little fat and protein for your body to use to build itself up. Eat nothing but salmon and brocolli, and you may well be in good health.
So the question is, are we eating better now than before? The answer to this is that the diet has in fact become worse for the average person. The packaged supermarket food, fast food from restaurants and boxed up breakfast cereals that dominate the modern UK diet are short on healthy ingredients and rich in unhealthy ones. The average person passing away this year will have experienced plenty of home cooked food. They were probably children during the war years and the austerity years that followed that. During this era meat and two veg for dinner was standard, fast food was not present with the exception of occasional fish and chips. Local produce was the norm as the U-boat blockage prevented imports.
While the diet was not perfect in the past it was much better than the average diet today. A diet consisting of meals from fast food outlets and packaged foods from supermarkets makes up much of todays intake. It contains unhealthy trans fats, excess salt and sugar as well as a host of relatively novel additives, some of which are intrinsically unhealthy. Lack of vitamins, minerals and omega 3 fats are greater than in the past3.
It is difficult to find studies that directly correlate the consumption of a healthy diet with life expectancy. This is because everyone has an individual diet that varies over time. However studies that compare diets in different countries suggest that the lack of healthy fats, too much sugar and lack of vitamins and minerals all have a very large impact on life expectancy, even for those of normal weight. As such I feel that the next generation in the UK is likely to experience greater mortality due to their diet than those dying today.
3. Lack of exercise.
With the advent of cars, TVs and computer games the population has become increasingly sedentary. At the same time the rise of supermarkets and death of groceries on the high street have reduced opportunities to exercise. Add to this the increasing amount of employment by large multi-national corporations that expect workers to work all the hours that god sends. As a result of all this the people dying today have, on average, had a much more active life than those who will die at the end of this century.
So does regular exercise increase your life span? You bet it does. It reduces risk of obesity, heart disease, stroke, some cancers and osteoporosis. These are the major causes of death in the West today.
As with healthy nutrition it is hard to find good studies that assess the value of exercise programs on longevity. Confounding factors abound in that many people who exercise are health concious and are also slimmer than those who don't. However, when you consider the measurable changes in hormones, blood lipids and feel good factors in the brain it seems unlikely that exercise does not confer a good boost to your life expectancy.
4. Human physiology.
There is no reason to suppose that people have not lived into their 100's throughout history. While proof is difficult from ages without formal birth records there is no reason to suppose that our ancestors were intrinsically less able to reach 100 than we are. However it is interesting to note that there is no firm evidence from the last 100 years of more than 1 person living over the age of 120. On the face of it there would seem to be a clock ticking for most people with a maximum battery life set at 120 years. For most people their maximum potential lifespan is not 120, but somewhat less.
People die at these great ages because their body parts literally wear out. There are accumulated changes to DNA that make cancers more likely. There are also changes in the DNA in populations of dividing cells that shorten their protective caps (telomeres). Consider your skin and intestines. Cells here divide regularly. Once their DNA is no longer protected by a telomere they will divide unreliably, and cancer or cell death will occur leading to deterioration of the skin/intestines.
I'm afraid that unless the Office of National Statistics is proposing we all have genetic therapy to make us live longer their projections are just wooly mumbo jumbo.
5. Overpopulation and climate change.
It isn’t the overcrowding so much as the war, pestilence and famine that Thomas Malthus predicted around 1800. Of course his vision of a worldwide cataclysm has not come about yet, but I personally am not betting against him. With population predicted to increase to between 9-15 billion4 in the next 100 years and economic growth set as the major goal of every economy there will be an inevitable squeeze on the earth's scarce resources. This will be exacerbated by rapid climate change.
It is almost impossible to predict when or where war, famine and consequent pestilence will occur. I feel that the UK cannot count itself to be immune to such possibilities over the next 100 years. The growth of the economies of India, China and Brazil are likely to shift prosperity away from the Europe and North America. As a smaller nation if resources become scarce elsewhere we may struggle if we are not self sufficient in food and energy.
So what will happen to life expectancy in a 1st world nation such as the UK over the next 100 years?
Firstly, I’m not too worried about novel infectious agents. With modern medicine and the fact that most infectious agents are not interested in killing their hosts as that rarely assists their survival, it seems likely that life expectancy will not be much impacted by that.
However, the combination of unhealthy diet, lack of exercise and consequent obesity I think puts a likely cap of 85 years on the peak of life expectancy in the UK. After that peak in about 2025 I expect the life expectancy in Britain to reduce down towards about 75 years. This represents the unhealthy, sedentary, obese types making up at least 50% of the population struggling to reach 75 years of age, while the others continue into their 80s and 90s. Beyond this life expectancy is more about luck and strong genes.
The above is of course ignoring the impact of overpopulation. While the impacts of global warming affecting the food and water supplies are undeniable, could technology save us from resource scarcity? I’m sceptical. I believe we have reached a tipping point already where resources are about to run short. Alternative resources will not be produced fast enough to replace resources that are running short. This will lead to the inevitable war, pestilence and famine. There will be winners and losers. If the UK is a loser then life expectancy could plummet.
Currently there are about 12,500 people over 100 in the UK. This figure represents about 1 in 5,000 of those in the UK. In other words your chance of being over 100 is 0.02%. If over 25% of the population lived to 100 then this could easily represent 1-2 million people being over 100 (I did a back of envelope calculation for this figure) and your chance of being over 1000 would be at least 2-3%. Yes, we do have an aging population, but to think that more than 25% of the population of the UK can live to 100 is pushing the bounds of credibility and understanding of what it takes to live to 100.