Those born today in a highly developed country with an effective health care system have about a one in three chance of living to be 100. The over 100 age group is advancing in size more rapidly on a percentage basis than any other age group.
In the last century probably the largest single reason for living longer and healthier lives and for having the chance to enter the over 100 group has been the marked increase in survival in childhood. Once past childhood steady improvements in health care dealing with the major chronic and debilitating diseases become important contributing factors to living longer, though secondary to childhood survival. In 1850 in America, life expectancy was reported to be 38 years of age. External conditions such as sanitation and some medical advances helped improve this number to 42 by 1890, 47 by 1900, 50 by 1920 and to 59 by 1930.
At the time of the invention and development of the sulfa-drugs and the discovery of penicillin life expectancy was still only about two thirds what it is now. In the early part of the 20th century, these drugs were immediately effective in stemming mortality in young children from major childhood infections. Development and widespread availability of immunization against major infections also helped. Gradually improvements in sanitation, diet and in the treatment chronic disorders affecting mortality in later life added to our chance of survival even while the major effect still continues as survival in childhood. Today life expectancy in America has improved to 79 when all races and all sexes are considered.
As we get even better at treating the chronic disabling conditions, we can look forward to squeezing life threatening disease further and further into the last years of life. This may also include preventative strategies such as not ingesting toxic substances with “foods,” drugs, addictions and the like, exercising, staying fit and generally avoiding severe frailty as long as possible. Dementia and brain diseases remain a particular challenge.
Gradually then, over the last century, we have substantially improved the chances of people born over the last 70-80 years of reaching past 100 years of age. Since 1950 world population has approximately doubled. Had there been no improvements in public health, we might expect the numbers of people surviving past age 100 to also approximately double. Thus, the number of people surviving past 100 years of age in 1950 would by now have expanded from 23,000 to about 46,000. However as of 2009 the numbers of people in the world surviving past 100 is at 455,000 or about 10 times more than we might have expected. This number may yet expand another 5 to 10 fold by mid century. The exact number will depend on continuing improvements in health factors associated with longevity. While the over 100 group (centenarians) should increase in a sizable way by 2050, the super-centenarians (those over 110) are still quite rare and those over 115 are rarer still. Those over 115 number are only 27-30 world wide. We don’t know enough about the general characteristics of the super-centenarians or those over 115 to say very much of general interest about what factors firmly contribute to their increased longevity. Those who are over 10o we have a more clear ideas about as a group.
Several factors contribute to a higher probability of individuals reaching the over 100 group, which is the most rapidly increasing group in the population. These include but may not be limited to a. family history (genetics), b. general health associated with life-style choices in behavior such as general diet with some increased emphasis on foods with antioxidant capacity, not smoking or using tobacco products, exercising and staying at or under proper weight, c. higher educational level, d. extroverted personality and e. those with a reduced history of stress. The largest numbers of centenarians currently are women who have never been married.
Thus, increasing life expectancy and living beyond the century mark in large numbers are both due in large measure to major medical and social advances, but are due also to additional genetic, environmental and behavior factors. Traditional views held in the middle of the 20th century that our work and major contributions to society begin to end at age 65 are changing, and will need to change our ideas about that even more going forward. More that likely we will see 65 increase to about 80 years of age, as a conventional way to think about retirement, over the early part of the current century when we should see medical costs begin to decline as serious medical problems are sent further and further to near end of life.