The recent increase in size of the centenarian population, happening as it did over a comparatively short period of time, is one measure of the steady increase in human life expectancy at older ages, achieved through progress in medical science and a growing wealth that grants access to the resulting treatments. The size of the very aged population is also subject to variations in the size of birth cohorts, however. It is far from true that the same number of people were born in every year over the past century, or even that the historical numbers are a smooth increase that matches the growth in overall population. The 1940s to 1960s saw a large rate of births in the US in comparison to later decades, for example. From the data for the first decades of the 20th century, a time of declining births in the US, we might expect the present centenarian population to fall over the next few decades if birth cohort size year after year were the only determinant. It isn't, of course.
In extreme old age, the greatest determinants of continued survival are at present some combination of genetics and use of medical technology. The latter will outstrip the former in its degree of influence over life span and health in old age, but over the course of recent decades gains in remaining life expectancy in old age have been very slow in coming. This is a trend of perhaps one year gained for every decade of progress when considering life expectancy at 60, for example. Such slow improvement is the result of a medical and research community that has focused on treating end stages of age-related disease without aiming for prevention in any significant way and without aiming to treat the true root causes, which is to say the processes of aging that produce accumulating cell and tissue damage. Patching over the problem of an age-related disease is expensive and produces marginal results: patches don't last when the damage, the underlying cause of the problem, continues to grow unaddressed.
This will change dramatically in the years ahead as rejuvenation technologies after the SENS model emerge from the laboratories. The difference between not treating the causes and treating the causes will be night and day in terms of the effects on age-related disease and mortality rates. A great upward discontinuity in life expectancy lies ahead, ultimately making the genetics of survival in old age irrelevant. After the advent of a complete toolkit of rejuvenation treatments capable of repairing the damage that causes aging, no-one will have to suffer in the state of being heavily damaged and on the brink of organ failure for years on end. In the average adult individual who bears little of that damage, currently only people not yet in their 40s, genetic variation has next to no effect on mortality rates.
More Americans than ever before are living past the age of 100, according to a new report (PDF) from the U.S. Centers for Disease Control and Prevention (CDC). The agency finds the number of the centenarians increased by 43.6 percent between 2000 and 2014 - from 50,281 to 72,197. Currently, there are some 317,000 centenarians worldwide, and that number is projected to rise to about 18 million by the end of this century, according to one report published in 2014.
In 2014, the top five causes of death among the oldest of the old were heart disease, Alzheimer's disease, stroke, cancer, influenza and pneumonia. Unfortunately, the number of super seniors dying from Alzheimer's disease continues to rise. Between 2000 and 2014, the rates of Alzheimer's disease-related deaths increased by 119 percent. Rates of deaths from other causes also spiked within the same time period, including hypertension (88 percent), chronic lower respiratory disease (34 percent) and unintentional injuries (33 percent). However fewer centenarians are dying from other causes. Between 2000 and 2014 the rate declined by 48 percent for influenza and pneumonia, 31 percent for stroke and 24 percent for heart disease.
National Vital Statistics System mortality data for years 2000 through 2014 were analyzed to determine the number of deaths, age-specific death rates by race and ethnicity, and sex-specific leading causes of death among centenarians. As the population in the United States has aged, the number of deaths among centenarians continues to increase. Death rates increased for both male and female centenarians from 2000 through 2008 and decreased from 2008 through 2014. Deaths for females accounted for more than 82% of total deaths each year, and females accounted for 80%-84% of the total centenarian population from 2000 through 2014. Heart disease remained the leading cause of death in 2014 as in 2000 for both male and female centenarians.