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Life Expectancy, Longevity and Lifespan: Is There a Difference?


Longevity, lifespan, and life expectancy are three terms that people sometimes use interchangeably.  All three terms relate to the number of years that someone is alive.  But that is where the similarities end.

What is life expectancy?

The definition of life expectancy is fairly simple:  life expectancy is how long a person can expect to live.  Your life expectancy is affected by personal factors such as environment, diet, age, gender, and genetics.  

At the time of this writing, the World Health Organization has set the average length of life at 72 years. The average life expectancy for someone in the United States is 79 years.  

What is longevity?

According to Merriam-Webster, the definition of longevity is a long duration of individual life or a length of life.   Someone who has the capacity to survive past the average age of death is said to have longevity. 

What is lifespan?

In science, the simplified definition of lifespan is how long a person COULD actually live.  Maximum lifespan is the oldest age that could be reached by an individual under ideal conditions.  That would mean no disease, no accidents, and the absolute perfect environmental conditions.  Of course, that isn’t possible.

Scientists can’t seem to agree on what the potential maximum lifespan could be.   Estimates are between 115 and 125.  The oldest person to ever have lived died at 122!

Life expectancy vs. Longevity vs. Lifespan

You can look at life expectancy, longevity, and lifespan in this order.

Life expectancy: How long you can expect to live.

Longevity:  How long you actually live past the average.

Lifespan:  How long you could potentially live.

It’s confusing and obvious as to why people mix the terms up!

The average life expectancy for a human is 72 years.  If you celebrate your 73rd birthday, you have a little bit of longevity, but nothing too impressive.  Keep in mind that an average would include people who died of very old age and people who died in childhood.  Depending on where you live and who you know, 72 doesn’t really seem that old.

Due to science, our life expectancy keeps going up.  In 1960, it was only 52.5 years!

Could I Live to be 100?

In short, yes.  In fact, it’s getting more and more likely that many of us will have that sort of longevity.

Someone who reaches age 100 is called a Centenarian. The Centenarian population is expected to grow eight times by 2050, according to a student in Current Geneaology and Geriatrics Research.  

It’s no secret that to get that old, you do need to take care of yourself and make choices that will benefit your long term health.  That said, genetics play a big part in how long you will live.  Studies show that genetics account for about 25% of longevity.  Having the right combination of genes significantly increases longevity.  But there is no single gene responsible for promoting a long life.  It seems like it’s the combination of genes and other factors. 

One of the factors that could affect how long you live is where you live.  According to the United Nations Department of Economic and Social Affairs China has the most people over 100.  The top five countries with the greatest number of Centenarians are:

  1. China

  2. Japan

  3. United States

  4. Italy

  5. India

Closing the Gap

We are closing the gap between lifespan and life expectancy thanks to ongoing scientific research.

Right now the average life expectancy in the world is hovering around 72 years and the potential human lifespan could be as much as 125 years.  That means, we could still have as many as 53 more years beyond the average!  That is almost a whole other lifetime.  

Maybe the old adage that “life begins at 60” could actually be true.

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