The truth about “Life Expectancy”

How many of you have come across this – “Life expectancy has increased significantly. Earlier the life expectancy used to be 35 years, now its 80 years. Things have changed, thanks to the technology, scientists and modern medicine, we have come a long way!”

Its not uncommon to associate life expectancy with quality of life, technological advancements, better healthcare services, and lifespan. This point comes up invariable when discussing about health in general, and I have always felt something wrong about this analysis.

It came again during the discussion post the screening of documentary “The Connection”.

This time I decided to dig a little deeper into this topic of Life Expectancy.


Life Expectancy at Birth by Region 1950-2050” by RcragunOwn work. Licensed under CC BY 3.0 via Wikimedia Commons.

So let’s look at what Life Expectancy is? First of all, there are various framework for life expectancy eg. Life Expectancy at Birth, or Life Expectancy at 12 or Life Expectancy at 60. According to WHO Life Expectancy at Birth is defined as “Average number of years that a newborn is expected to live if current mortality rates continue to apply.”

What we generally refer to as “average life expectancy” is technically “life expectancy at birth” – the average number of years a newborn baby will live at a given time. But then calculating this at birth is no good, if we want to get an idea of the health and longevity of adults. The child mortality rate in the past was quiet high and hence the life expectancy at birth was drastically low.

When we say that average life expectancy in past was 35 years, does it means that average person living during that time died at the age of 35? No, that simply means that if one kid died at the time of birth (infant mortality) there was one person who lived up to 70 and that averages out to 35. It by no means represents the quality of life, neither does it represents the lifespan.

Similarly if one kid dies at the age of 10 and another person lived till 70, the life expectancy at birth will be 40. Now over past many decades, the infant mortality rate has reduced significantly and the medical system has helped people live longer, while in the past, they would have died. So the death rate has also come down. Both these factors affect life expectancy. And since life expectancy at birth is greatly affected by infant death, if you were to calculate it at the age of 10 or 15 years it will rise drastically.

Let me put it the other way – there were 100 kids born and half of them, 50 kids died before the age of 10. Lets assume that the average age of death for these 50 kids is 5 years. The remaining 50 kids went on to live an average life of 65, the life expectancy at birth will be 35. This also means that out of the remaining 50 kids, many would have lived past 65, resulting in that age as an average. So what does this signify? Life expectancy at birth of 35 in a given society does not mean that a 15 year old can expect to live only for 20 more years. For all you know that 15 year old can expect to live for another 50 years.

So when it is said that life expectancy has increased as compared to what it used to be, for me it only means that less kids are dying when they are born and more people are living longer (even a person who is in coma for 20 years is helping increase the life expectancy).

What’s your thought on this?

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