Posts Tagged ‘longevity’

The “design life” of humans

March 25, 2016

The “design life” of a component or system is generally a boundary condition before starting to design. It is an inherent part of the design. The human body can be taken to be a system based on the organs as major components and a myriad of other components. Our genes are the design for our bodies and they exhibit a “design life”. Whatever we may assign as the purpose of our DNA, our bodies exhibit a design life of between 50 and 60 years. 

In engineering, when an artefact or component or system is created, it is quite usual to have a “design life” as one of the key boundary conditions for designing the artefact. The artefact-lifetime to be designed for determines the choice of materials for strength and resistance to corrosion and erosion, and for their cycling properties and their resistance to fatigue and creep. The lifetime to be designed for leads to a choice for the level of redundancies to be included, the ease of maintenance to be allowed for and a choice of a maintenance strategy which includes a replacement “philosophy”. The “design life” is then usually defined as the time for which the artefact will be fully functional and can often be the lifetime guaranteed by the manufacturer. The designer makes his choices based on the probability of failures. For example the quoted design-life may be based on the time when the probability of failure or loss of functionality is – say – less than 10% or 1% or 0.1%.

The concept of “design-life” is different to the concept of “obsolescence” or the “mean time between failures” (MTBF). Obsolescence, whether introduced intentionally or not, is the time when when the defined functionality is no longer relevant. It could be intentionally “built-in” as a marketing strategy or it may result from the appearance of new technologies. The MTBF is a measure of the time between random – not due to wear – failures of a particular component. The MTBF of single components will generally be orders of magnitude longer than the design-life of that component.

Most components or systems can – with proper maintenance – be used with full functionality long beyond their quoted design life. A power plant may have a design life of 25 years, guarantees for only 2 years but may be used for 50 or 60 years. A digital camera may have a design life of 5 years but could be obsolete after just three. A Swatch may have a design-life of 5 years and materials to suit, whereas a Rolex may use materials and manufacturing quality to be able to come with a lifetime guarantee (with suitable caveats for the user’s negligence). When analysing reliability, the life of components and systems is often illustrated by the generic “bathtub curve”, where the total failure rate is given by the addition of random failures, failures due to “infancy problems” and failures due to wear. Infancy issues are those which are caused by quality of materials, manufacturing tolerances, manufacturing processes and the like.

Modes of failure

On the bathtub curve the design life used to create a design will always fall within the section where the total failure rate is at its lowest – that is after the initial period where “teething” and other infancy problems arise and before the sharp increase in failure due to wear. Generally, to change the design life the basic design itself must be changed.

Consider the human body as a system where the organs are the key components making up the system. The functionality of human organs and of different human functional abilities also exhibit a form very similar to a reversed “bathtub” curve. Failure of a human body occurs when one or more of the functionalities falls below some threshold minimum. In the diagram below, the shaded area represents the behaviour of most organs with age. The lines represent the variation of some of the complex human functional abilities with age.

Functionality of organs with age

Functionality of organs with age

The reverse bathtub curve suggests that the human body has a design life of between 50 and 60 years.

“Infancy problems” in this context include birth and genetic defects which can influence the development and failure rate of organs. “Wear” would be the physical and mental wear and tear but would now also include the effects of aging which curtail the replacement of cells. Average, global, life expectancy is now around 80 years and the longest verified age is about 122 years. Average life expectancy has increased over the last 200 years at the rate of about 3 months every year. Over the next 100 years this may level off to perhaps add another 20 years to life expectancy. Already in 2012 the UN estimated that there were more than 300,000 centenarians alive. By 2100 perhaps global life expectancy would have reached 100 years and the maximum age attained may then be around 140-150 years.

Using the engineering analogy, the main advances in life expectancy have so far come due to improving maintenance and replacement processes but have not improved on the “basic design”. The “improved quality” at birth and in infancy and medical advances have meant that “maintenance” processes have improved drastically. Modern health care is to a large extent the application of “preventive maintenance”.

But, the the basic design is unchanged. The materials used in making up the human body have not changed but “maintenance and repair” strategies have improved out of all recognition. The life of our various organs have not changed inherently, except as a result of the much improved maintenance regime. With no change in basic design, the design life has not changed either. The increasing lifetime of the system (the body) is now beginning to approach the lifetime of the components (the organs) it is made up of.

Currently the design life of a human body could be said to be about 50-60 years. Studies suggest that though we live longer we also have longer periods at the end of our lives when our functionality is severely impaired. The ” basic design” has not changed and the “design life” is not increasing. Life spans of 200 years will not be possible without some change in the “basic design”. For our design life to change it will need advances which allow our cells to keep replicating without the aging effects of the shortening of the telomeres. When that happens (not if), then we would effectively have altered the “basic design” of the human body and its design life.



UK longevity increasing faster than national statistics forecasts

April 30, 2015

The rule-of-thumb is that average longevity in a developed country increases by about 1 year every 25 (4 years every century). So in the year 2500 an average longevity should be well over 100 years. It has been postulated that that this rate of longevity increase will decrease as we approach some kind of asymptotic “maximum possible” age – variously proposed to be 100, 150 or even 200 years. But it seems that the understanding of how telomeres affect cell aging and cancer is also fast increasing. If medical science develops to the extent that key cells can be encouraged to renew themselves in a controlled manner (by not reducing the telomere tail in a cell’s DNA with every replication) and yet not succumbing to the risk of uncontrolled growth (cancer), then a human longevity of even 500 years  does not seem impossible.

After 2100 the world will be faced with a fertility rate below replenishment levels and one way of mitigating the effects of a declining population will be an increasing longevity and a corresponding increase in the span of the “child-bearing” years (which in turn will correct the fertility decline). The challenge is going to be in arresting the decline of human faculties. If that is achieved it will automatically increase the “productive life span” and balance the critical and currently declining ratio of productive population to supported population.

A new paper in The Lancet suggests that official statistics in the UK are underestimating the rate at which longevity is increasing. 

J.E. Bennett et al. ‘The future of life expectancy and life expectancy inequalities in England and Wales: Bayesian spatial forecasting of population health.’ Lancet, 2015.

Imperial College has put out a press release:

A new study forecasting how life expectancy will change in England and Wales has predicted people will live longer than current estimates.

The researchers say official forecasts underestimate how long people will live in the future, and therefore don’t adequately anticipate the need for additional investments in health and social services and pensions for the elderly.

The new study, published in the Lancet, also predicts that regional inequality in life expectancy will increase, highlighting a need to help deprived districts catch up with affluent areas.

Researchers at Imperial College London developed statistical models using death records, including data on age, sex, and postcode, from 1981 to 2012 to forecast life expectancy at birth for 375 districts in England and Wales.

They predict that life expectancy nationally will increase for men from 79.5 years in 2012 to 85.7 in 2030, and for women from 83.3 in 2012 to 87.6 in 2030. The longevity gap between men and women has been closing for nearly half a century and will continue to get narrower.

The forecasts for 2030 are higher than those by the Office of National Statistics, by 2.4 years for men and 1.0 year for women. …

During my life-time, “middle age” has shifted from 40 years to be now around 50. For my children “middle age” will probably be at around 60.

A retirement age of 78 will be needed in Norway for children born today

January 23, 2013

Increasing lifespans are real and the period during which we can be productive is increasing and what follows is inevitable. At the present rate of longevity increasing by about 3 months every year, by 2500 most people will live to be 200. Considering that world population is likely to be falling slowly after 2100 it seems not unconnected that any consequent decrease in human economic activity will be (will have to be) compensated for by people having a longer productive life.

A year ago a trial balloon was sent up by the Swedish Prime Minister when he imagined a retirement age of 70 rather than the current 65. Now a suggestion that retirement age will have to be increased to 78 has been floated in Norway. The necessary debate is starting but the result is not in doubt – only the timing is.

But before not too long the  human condition of “study for 20 work for 40 and live to 80”  which probably applies to me will change to “study for 25, work for 50 and live to 100” and will apply to my children. And probably within another 200 years it would have become “study for 40, work for 80 and live to 160”.

Svenska Dagbladet:

Work until you’re 78. It could become necessary for Norwegians born today if the financial burden on the productive section of the population is not to become too large. The calculation and the challenge is from the Norwegian business newspaper Dagens Industry and has created a heated debate in Norway.

Life expectancy is on the rise in both Sweden and Norway. It will force today’s young people to work longer than today. But to retire at 78 years of age is not what many are convinced about.  Sweden had a similar debate when Prime Minister Fredrik Reinfeldt spoke of 75 years as an appropriate retirement age.

In Norway, the suggestion is that 78 years is the appropriate age but Professor Hilde Björnland has doubts: “ The calculation is interesting because it shows the increased pension obligations we face. It is not enough to work up to age 67 if we are to cope with the coming demographic challenges”. But, she says, there is a difference between a long life and increasing mental and physical health. It is uncertain whether we can work much longer than 65-70 years even though we live longer. It depends on how the jobs look like in the future, it depends on how the tasks are suited to us as we get older. Today, only 2.3 percent of the Norwegian population work between 67 and 74 years. After 74 years, it is so small that it is not measurable by the Norwegian Central Statistical Office.

Those who want to raise the retirement age to 78 years at Den Norske Bank believe in any case that today’s young people must be prepared to work much longer than their parents’ generation did. But to get people to work more years in a country that has huge oil revenues and would like to convert income to more leisure time will not be easy. … 

Wow! “Scientific study” reveals that healthy people live longer

December 17, 2012

This has been published in the BMJ today so it obviously has been “peer-reviewed” before publication. Crunch a little data (why only Olympic medalists and not all Olympic participants?), do some elementary statistics and come up with something profoundly obvious and it passes for “science”. It took no less than six authors!!

Survival of the fittest: retrospective cohort study of the longevity of Olympic medallists in the modern era, by Philip M Clarke, Simon J Walter, Andrew Hayen, William J Mallon, Jeroen Heijmans, and David M Studdert. BMJ 2012; 345

doi: (Published 13 December 2012)

15 174 Olympic athletes from nine country groups (United States, Germany, Nordic countries, Russia, United Kingdom, France, Italy, Canada, and Australia and New Zealand) who won medals in the Olympic Games held in 1896-2010. Medallists were compared with matched cohorts in the general population (by country, age, sex, and year of birth).

Results More medallists than matched controls in the general population were alive 30 years after winning (relative conditional survival 1.08, 95% confidence interval 1.07 to 1.10). Medallists lived an average of 2.8 years longer than controls. Medallists in eight of the nine country groups had a significant survival advantage compared with controls. Gold, silver, and bronze medallists each enjoyed similar sized survival advantages. Medallists in endurance sports and mixed sports had a larger survival advantage over controls at 30 years (1.13, 1.09 to 1.17; 1.11, 1.09 to 1.13) than that of medallists in power sports (1.05, 1.01 to 1.08).

Conclusions Olympic medallists live longer than the general population, irrespective of country, medal, or sport. This study was not designed to explain this effect, but possible explanations include genetic factors, physical activity, healthy lifestyle, and the wealth and status that come with international sporting glory.

The discussion is remarkably mundane and offers little insight into anything:

One explanation is that athletes are much healthier than the average person. Part of this advantage could be genetic, but environmental factors undoubtedly amplify genetic advantages. Young athletes who exhibit exceptional physical talents are often selected into national training squads to undergo intensive physical training over many years. Most Olympic medallists will have come through such programmes.

Strong evidence indicates that physical activity confers many health benefits, including improved functional health status and reduced risks of cardiovascular disease, coronary heart disease, stroke, depression, type 2 diabetes, and breast and colon cancer ………

Ah well! One more publication to add to the list.

The price of longevity is degradation of the elderly

October 7, 2012

The care of the elderly passing from family members to institutions is one of the apparently irreversible  developments in all cultures today. It is not just a phenomenon of “Western” civilization but is a trend across the globe. As “joint families” have given way to nuclear families and as couples have both gone out “to work” and as the elderly desire greater independence and as people live longer, the responsibility for the care of the elderly has passed to institutions from ever-more burdened children or relations.

But a model for institutional care – whether by private players or the State – which works without the degradation of the elderly has yet to be found. I suppose the fundamental reasons are that

  1. to die quietly and with some dignity and with as little discomfort as possible is only of value to the dying,
  2. those who are “in care” have limited opportunities to make themselves heard, let alone to complain,
  3. those “in care” are no longer worth very much to the society they live in and are only seen as a cost,
  4. even for the relatives and children of those in institutional care, the elderly are seen primarily as “duties”  and they would rather not complain if the only solution is a responsibility devolving upon themselves, and
  5. for institutions providing care there is always a  financial benefit to not providing care and they get no “extra bonus” when they do provide care.


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