A centenarian is a person who lives to or beyond the age of 100 years. Because current average global life expectancies are less than 100, the term is invariably associated with longevity. A supercentenarian is a person who has lived to the age of 110 or more, something only achieved by about one in 1,000 centenarians. Even rarer is a person who has lived to age 115; , there are only 27 people in recorded history who have indisputably reached this age. In 2009, the United Nations estimated that there were 455,000 living centenarians worldwide.

Current incidence

The United States currently has the greatest number of centenarians of any nation, estimated at 70,490 on September 1, 2010. This corresponds to a national incidence of one centenarian per 4,400 people.

Japan has the second-largest number of centenarians, with an estimated 47,756 as of September 2011. Japan started its surveys in 1963, at which time the number of Japanese centenarians was found to be 153. This number surpassed the 10,000 mark in 1998, 20,000 in 2003, and 40,000 in 2009. According to a UN Demographic survey, Japan is expected to have 272,000 centenarians by 2050. However, some sources suggest that the number could be closer to 1 million. Many experts attribute Japan's high life expectancy to the Japanese diet, which is particularly low in refined simple carbohydrates, and to hygienic practices. In addition, the number of centenarians in relation to the total population was, in September 2010, 114% higher in Shimane Prefecture than the ratio for the whole of Japan. This ratio was also 92% higher in Okinawa Prefecture. In addition to diet, there are four other factors that have been found to increase the life expectancy for Okinawans, as noted later in the "research into centenarians" section of this article. The incidence of centenarians in Japan was one per 3,522 people in 2008, although Okinawa again exceeded this average, with one per 1,838 people in 2006.

Centenarian controversy in Japan

The number of Japanese centenarians was called into question in 2010, following a series of reports showing that hundreds of thousands of elderly people had gone "missing" in the country. The deaths of many centenarians had not been reported, casting doubt on the country's reputation for having a large population of centenarians.

In July 2010, a centenarian listed as the oldest living male in Tokyo, registered to be aged 111, was found to have died some 30 years before; his body was found mummified in its bed, resulting in a police investigation into centenarians listed over the age of 105. Soon after the discovery, the Japanese police further found that at least 200 other Japanese centenarians were missing, with the total likely to rise amid a nationwide search that began in early August 2010. In one case, the remains of a mother thought to be 104 had been stuffed into her son's backpack for nearly a decade.

There are growing concerns that Japan's welfare system can be exploited by unscrupulous family members keen to continue receiving benefits after the pensioners die. In one case, a man received around 9.5 million yen in pension payments despite his wife having died six years previously.

Centenarian populations

The total number of centenarians in the world remains uncertain. It has been estimated by the Population Division of the United Nations as 23,000 in 1950, 110,000 in 1990, 150,000 in 1995, 209,000 in 2000 and 324,000 in 2005. There were an estimated 455,000 centenarians in the world in 2009. However, these estimates do not take into account the recent downward adjustments of national estimates made by several countries, such as the United States. The following table lists estimated centenarian populations by country, including both the latest and the earliest known estimates, where available.

{|class="wikitable" |- !Country !! Latest estimate (year) !! Earliest estimate (year) |- |Argentina|| 3,487 (2010 census)|| - |- |Australia|| 4,252 (30 June 2011) || 203 (30 June 1971) |- |Belgium|| 1,559 (1 January 2010) || 546 (1990) |- |Brazil|| 23,760 (17 September 2010) || 13.865 (1991) |- |Canada|| 7,569 (1 July 2011) || 3,125 (2001) |- |China || Various estimates: 17,800 (2007); 48,921 (1 July 2011)|| - |- |Czech Republic || 625 (30 Sept. 2011) || - |- |France|| 17,564 (1 January 2012) || 7,754 (1 January 1999) |- |Germany||8,839 (2006)||232 (1885) |- |Hungary||799 (2009)||227 (1990) |- |Italy || 6,313 (2001) || - |- |Japan || 44,449 (September 2010) || 155 (1960) |- |Netherlands|| 1,743 (2010) || 10 (1900) |- |Peru|| 1,682 (7 February 2011) || - |- |Poland|| 2,414 (25 July 2009)|| 500 (1970) |- |South Korea|| 961 (2005) || - |- |Spain || 5,891 (1 January 2009)|| - |- |Sweden|| 1500 (2009)|| - |- |Switzerland || 796 (2000)|| 10 (1860) |- |UK || 12,640 (mid-2010) || 102 (1911) |- |USA|| 70,490 (September 2010)|| 2,300 (1950) |}

Traditions

In many countries, people receive a gift or congratulations on their 100th birthday. In the United States, centenarians traditionally receive a letter from the President, congratulating them for their longevity. NBC's ''The Today Show'' show has also named new centenarians on air since 1983. In the United Kingdom and the Commonwealth Realms, the Queen sends greetings (formerly as a telegram) on the 100th birthday and on every birthday starting with the 105th. Centenarians born in Ireland receive a €2,540 "Centenarians' Bounty" and a letter from the President of Ireland, even if they are resident abroad. Japanese centenarians receive a silver cup and a certificate from the Prime Minister of Japan upon their 100th birthday, honouring them for their longevity and prosperity in their lives. Swedish centenarians receive a telegram from the King and Queen of Sweden. Centenarians born in Italy receive a letter from the President of Italy. In Japan, a "National Respect for the Aged Day" has been celebrated every September since 1966.

An aspect of blessing in many cultures is to offer a wish that the recipient lives to 100. Among Hindus, people who touch the feet of elders are often blessed with "May you live a hundred years". In Sweden, the traditional birthday song states, ''May he/she live for one hundred years.'' In Judaism, the term ''May you live to be 120 years old'' is a common blessing. In Poland, ''Sto lat'', a wish to live a hundred years, is a traditional form of praise and good wishes, and the song "sto lat, sto lat" is sang on the occasion of the birthday celebrations--arguably, it is the most popular song in Poland and among Poles around the globe. Chinese emperors were hailed to live ten thousand years, while empresses were hailed to live a thousand years. In Italy, "A hundred of these days!" (''cento di questi giorni'') is an augury for birthdays, to live to celebrate 100 more birthdays. Some Italians say "Cent'anni!", which means "a hundred years", in that they wish that they could all live happily for a hundred years. In Greece, wishing someone Happy Birthday ends with the expression ''να τα εκατοστήσεις'' (''na ta ekatostisis''), which can be loosely translated as "may you make it one hundred birthdays".

Centenarians in ancient times

While the density of centenarians per capita was much less in ancient times than today, the data suggest that reaching the age of 100 was not unheard of. However, ancient demographics are biased in favor of wealthy or powerful individuals rather than the ordinary person. Grmek and Gourevitch speculate that during the Classical Greek Period, anyone who made it past the age of five years — surviving all the common childhood illness of that day — had a reasonable chance of living to a ripe old age. Life expectancy at 400 B.C. was estimated to be around 30 years of age. One demographer of ancient civilizations reported that Greek men lived to 45 years (based on a sample size of 91), while women lived to 36.2 years (based on a sample size of 55). Curiously, the gender statistics are inverted compared to today, since child-birth was a much more traumatic experience at that time than now, and it certainly skewed female statistics downward. It was common for average citizens to take great care in their hygiene (sanitation), Mediterranean diet (fish, figs, olive oil, wine, etc.), and exercise program (sports/gymnasium), although there was much more male trauma per capita than today, due to military service being virtually universal for citizens. This also biased the statistics for men downward.

Diogenes Laertius (c. 250) gives one of the earliest references regarding (''plausible'' centenarian) longevity given by a scientist, the astronomer Hipparchus of Nicea (c. 185 – c. 120 B.C.), who, according to the doxographer, ''assured'' that the philosopher Democritus of Abdera (c. 470/460 – c. 370/360 B.C.) lived 109 years. All other accounts about Democritus given by the ancients appear to agree on the fact that the philosopher lived over 100 years. Such longevity would not be dramatically out of line with that of other ancient Greek philosophers thought to have lived beyond the age of 90 (e.g.: Xenophanes of Colophon, c. 570/565 – c. 475/470 B.C.; Pyrrho of Ellis, c. 360 - c. 270 B.C.; Eratosthenes of Cirene c. 285 – c. 190 B.C., etc.). The case of Democritus differs from the case of, for example, Epimenides of Crete (7th, 6th centuries B.C.), who is said to have lived an implausible 154, 157 or 290 years, depending on the source.

The sixth dynasty Egyptian ruler Pepi II is believed by some Egyptologists to have lived to the age of 100 or more (c. 2278 BC - c. 2184 BC), as he ruled for 94 years. However this is under dispute, as others claim the length of his reign was actually 64 years.

The Indian Sufi poet, Kabir (1398-1518?) is believed by some to have lived to an implausible age of 120 while others believe that he lived for no more than 80 years.

Ultimately, there is no reason to believe that centenarians did not exist 2500 years ago, even if they were not commonplace.

Hosius of Córdoba, the man who convinced Constantine the Great to call the First Council of Nicaea, reportedly lived to age 102.

The ''Chronicon'' of Bernold of Constance records the death in 1097 of ''Azzo marchio de Longobardia, pater Welfonis ducis de Baiowaria'', commenting that he was ''iam maior centenario''.

Research into centenarians

Research carried out in Italy suggests that healthy centenarians have high levels of vitamin A and vitamin E and that this seems to be important in guaranteeing their extreme longevity. Other research contradicts this, however, and has found that these findings do not apply to centenarians from Sardinia, for whom other factors probably play a more important role. A preliminary study carried out in Poland showed that, in comparison with young healthy female adults, centenarians living in Upper Silesia had significantly higher red blood cell glutathione reductase and catalase activities and higher, although insignificantly, serum levels of vitamin E. Researchers in Denmark have also found that centenarians exhibit a high activity of glutathione reductase in red blood cells. In this study, those centenarians having the best cognitive and physical functional capacity tended to have the highest activity of this enzyme.

Other research has found that people having parents who became centenarians have an increased number of naïve B cells. It is well known that the children of parents who have a long life are also likely to reach a healthy age, but it is not known why, although the inherited genes are probably important. A variation in the gene FOXO3A is known to have a positive effect on the life expectancy of humans, and is found much more often in people living to 100 and beyond - moreover, this appears to be true worldwide.

Men and women who are 100 or older tend to have something else in common, an extraverted personality, says Thomas T. Perls, M.D., M.P.H., the director of the New England Centenarian Study at Boston University. Centenarians will often have many friends, strong ties to relatives and a healthy dose of self-esteem.

Some research suggests that centenarian offspring are more likely to age in better cardiovascular health than their peers.

In John W. Santrock's book "A Topical Approach to Life-Span Development", there are five factors that research has suggested that are most important to longevity in centenarians: 1) heredity and family history 2) health, i.e. weight, diet, whether or not a person smokes, amount of exercise 3) education level 4) personality 5) lifestyle.

Santrock's book also noted that the largest group of centenarians are women who have never been married. Also, people who have been through traumatic life events, such as Holocaust survivors, learn to cope better with stress and poverty and are more likely to reach centenarian status.

In Okinawa, Japan, studies have shown five factors that have contributed to the large number of centenarians in that region: # A diet that is heavy on grains, fish, and vegetables and light on meat, eggs, and dairy products. # Low-stress lifestyles, which are proven significantly less stressful than that of the mainland inhabitants of Japan. # A caring community, where older adults are not isolated and are taken better care of. # High levels of activity, where locals work until an older age than the average age in other countries, and more emphasis on activities like walking and gardening to keep active. # Spirituality, where a sense of purpose comes from involvement in spiritual matters and prayer eases the mind of stress and problems.

Although these factors vary from those mentioned in the previous study, the culture of Okinawa has proven these factors to be important in its large population of centenarians.

See also

Lists of centenarians

New England Centenarian Study

Okinawa Centenarian Study

Oldest people

Queensland Community Care Network, which operates the centenarians-only 100+ Club

Research into centenarians

References

Further reading

External links

The Okinawa Centenarian Study

New England Centenarian Study

Living to 100 and Beyond: Search for Predictors of Exceptional Human Longevity

Mortality of Centenarians

U.S. politicians who lived the longest

Noted Nonagenarians and Centenarians

Centenarian research & celebration

Living Beyond 100 - International Longevity Center UK

Table of numbers of centenarians for select nations, 1960 and 1990

Centenarians’ Road

*Centenarians

es:Centenario (persona) eo:Centjarulo fa:افراد صدساله fr:Centenaire ko:백세인 it:Centenario pl:Stulatek ru:Знаменитые долгожители simple:Centenarian zh:人瑞