Ladies and Gentlemen! Welcome to Centenarian Club. The first rule of Centenarian Club is: Live to 100.

This is not some twisted version of Fight Club, a movie in which the character, Tyler Durden, escapes from his mundane life by fighting other men in a secret underground club. While Fight Club was likely cathartic for its members, it is a probably not a model for how to live a long life. The Centenarian Club is quite the opposite, and celebrates human longevity and health.

During the early 20th century, average life expectancy was around 30 years. In our current era, many of us have the luxury of an average life expectancy of 67 years (80-85 years in developed countries). This increase in lifespan is due to a number of societal, technological, and economical advances including reduced mortality rates in infants and children, improved education, improved lifestyle, as well as economic and political factors. As our quality of life and understanding of the impact of lifestyle choices has drastically improved over time, so have health and longevity. Check out the following statistics:

  • As of 2012, an estimated 316,600 centenarians exist around the world.
  • One in three babies born now will live to be centenarians in the UK.
  • The current centenarian population is 80% women.
  • The US has the largest Centenarian population with 53,364 recorded in the 2010 census (17.3 in 100,000 people).

But despite the fact that lifespans are generally increasing, they are not increasing uniformly. Some people who live healthy lives die in their 60’s and 70’s of diseases like cancer and Alzheimer’s, while others who seem to engage in bad habits maintain their physical and mental health into their 80’s and 90’s. How is it that some live so much longer than others? And how is it that more and more people are living past 100?

Photo credit: Seth Joel Photo source: The Guardian

Photo credit: Seth Joel
Photo source: The Guardian

Let’s take a look at one of the most well known centenarians, Jeanne Calment. Calment was actually a supercentenarian who lived to the age of 122 (which currently is the longest confirmed human lifespan). She spent her life in France and outlived her husband and all her offspring. Contrary to most peoples’ expectations, Calment stayed healthy well in to her late age. She picked up fencing at the age of 85, rode her bike until she was 100, and stubbornly kept up her smoking habit until she was 117. During this time, she never was afflicted with a serious disease and maintained her mental capacity until she died. How is this possible? Was it her laid-back lifestyle, diet, or exercise regimen? Her impressive lifespan is likely due to a combination of these factors. Interestingly, it was documented that Calment came from a family of long-lived persons, which suggests a genetic component might be at play as well.

Speaking of genetics, scientists are now turning to centenarians themselves to identify genetic factors that promote human longevity. By sequencing the genomes of these individuals, scientists have identified genetic factors that may positively or negatively influence lifespan. Many of these factors were first identified in laboratory models of aging such as yeast (S. cerevisiae; the workhorses of the bread and beer industry) and worms (C. elegans, microscopic worms commonly found in garden soil). While these organisms are pretty far from humans, they both have important biological similarities to humans while being vastly easier to study in a dish; S. cerevisiae behaves a lot like isolated human cells do, and C. elegans has many of the same tissue types while having a much simpler body architecture. By screening these models for genes associated with longevity, a number of genes have been identified including sirtuins, the insulin/IGF1 pathway, FOXO3A, and APOE. Each of these genes or pathways deserves its own blog, but in brief, genetic mutations that decrease activity of the insulin/IGF pathway and mutations that increase activity of SIR-2 and FOXO3A are associated with an extension in lifespan. APOE is an especially interesting case. This gene is well known for its association with cardiovascular disease and Alzheimer’s disease. With regards to lifespan, the one “version” of APOE–there are three versions, or alleles, of this gene: E2, E3, and E4–APOE4 was found in significantly fewer centenarians while the E2 allele appeared at a much higher frequency compared to a normal population.

Scientists are rapidly identifying other longevity-associated factors from data on centenarians (See the New England Centenarian Study and published studies here, here, and here) and testing whether any of these factors are suitable targets for anti-aging therapeutics. But what about those of us who aren’t blessed with lifespan extending genetics? Lifestyle changes like exercise, improved diet, and avoiding bad habits such as drinking excessive amounts of alcohol or smoking will generally help a person live longer. Additionally improvements in preventative healthcare and scientific advances in the understanding and treatment of diseases are already adding years to our lives.

So while more and more humans are likely to join the Centenarian Club, it’s important to also consider critical issues such as improving the quality of life at 100 years and what this phenomenon means demographically and environmentally. Is a longer life beneficial if the last decades are spent in an enfeebled state? How will our world cope with a fast-growing elderly population that has increasing health needs and limited ability to contribute to the work force? These are all important and difficult questions to be faced in the near future. Finding a cure to aging may solve some of these issues and allow more people to join the Centenarian Club, it is not yet a reality and when it is it will create a new set of moral and ethical dilemmas regarding the future of our species.