Centenarian

Current incidence

The United States currently has the greatest number of known centenarians of any nation with 53,364 according to the 2010 Census, or 17.3 per 100,000 people. In 2010, 82.8% of US centenarians were female. Japan has the second-largest number of centenarians, with an estimated 51,376 as of September 2012, and the highest proportion of centenarians at 34.85 per 100,000 people. Japan started recording its centenarians in 1963. The number of Japanese centenarians in that year was 153, but surpassed the 10,000 mark in 1998; 20,000 in 2003; and 40,000 in 2009. According to a 1998 United Nations demographic survey, Japan is expected to have 272,000 centenarians by 2050; other sources suggest that the number could be closer to 1 million. The incidence of centenarians in Japan was one per 3,522 people in 2008.

Gender skew

In Japan, the number of centenarians is highly skewed towards females. Japan in fiscal year 2016 had 57,525 female centenarians, while males were 8,167, a ratio of 7:1. The increase of centenarians was even more skewed at 11.6:1.

Centenarian populations by country

The total number of living centenarians in the world remains uncertain. It was 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, 324,000 in 2005 and 455,000 in 2009. However, these older estimates did not take into account the contemporary downward adjustments of national estimates made by several countries such as the United States; thus, in 2012, the UN estimated there to be only 316,600 centenarians worldwide. The following table gives estimated centenarian populations by country, including both the latest and the earliest known estimates, where available.

British and Commonwealth traditions

In many countries, people receive a gift or congratulations on their 100th birthday. In the United Kingdom and the other Commonwealth realms, the British (and Commonwealth) monarch sends greetings (formerly as a telegram ) on the 100th birthday and on every birthday beginning with the 105th. The tradition of Royal congratulations dates from 1908, when the Secretary for King Edward VII sent a congratulatory letter to Reverend Thomas Lord of Horncastle in a newspaper clipping, declaring, "I am commanded by the King to congratulate you on the attainment of your hundredth year, after a most useful life." The practice was formalised from 1917, under the reign of King George V, who also sent congratulations on the attainment of a 60th Wedding anniversary. Queen Elizabeth II, sends a greeting card style with the notation "I am so pleased to know that you are celebrating your one-hundredth birthday, I send my congratulations and best wishes to you on such a special occasion", there after each few years the card is updated with a current picture of her majesty as to ensure people do not receive the same card more than once. The Queen further sends her congratulations on one's 105th birthday and every year thereafter as well as on special wedding anniversaries, people must apply for greetings 3 weeks before the event, on the official British Monarch's website

United States and other

In the United States, centenarians traditionally receive a letter from the President, congratulating them for their longevity. NBC's Today Show has also named new centenarians on air since 1983. 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.

Religious rituals

An aspect of blessing in many cultures is to offer a wish that the recipient lives to 100 years old. 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 and three months 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 sung 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 number of centenarians per capita was much lower in ancient times than today, the data suggest that they were not unheard of. However, ancient demographics and chronicles are biased in favor of wealthy or powerful individuals rather than the ordinary person. A rare glimpse of an ordinary person is the legionary veteran Julius Valens whose tombstone states he lived 100 years - "VIXIT ANNIS C". Grmek and Gourevitch speculate that during the Classical Greek period, anyone who lived past the age of five years – surviving all the common childhood illnesses of that era – had a reasonable chance of living to a relatively old age. Life expectancy in 400 BC was estimated to be around 30 years. One demographer of ancient civilizations reported that Greek men lived to 45 years on average (based on a sample size of 91), while women lived to 36.2 years (based on a sample size of 55). Notably, the gender statistics are inverted compared to today – childbirth at the time had a far higher mortality rate than in modern times, skewing female statistics downward. It was common for average citizens to take great care in their hygiene, Mediterranean diet and exercise, although there was much more male trauma per capita than today, due to military service being virtually universal for citizens of Ancient Greece. This also biased the statistics for men downward.

Diogenes Laertius (c. AD 250) gives one of the earliest references regarding the plausible centenarian longevity given by a scientist, the astronomer Hipparchus of Nicea (c. 185 – c. 120 BC), who, according to the doxographer, assured that the philosopher Democritus of Abdera (c. 470/460 – c. 370/360 BC) lived 109 years. All other ancient accounts of Democritus appear to agree that the philosopher lived at least 90 years. However, 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 BC; Pyrrho of Ellis, c. 360 - c. 270 BC; Eratosthenes of Cirene c. 285 – c. 190 BC). The case of Democritus differs from those of, for example, Epimenides of Crete (7th and 6th centuries BC), who is said to have lived an implausible 154, 157 or 290 years, depending on the source.

Numerous other historical figures were reputed to have lived past 100. The sixth dynasty Egyptian ruler Pepi II is believed by some Egyptologists to have lived to 100 or more (c. 2278 – c. 2184 BC), as he is said to have reigned for 94 years. However this is disputed: others say he only reigned 64 years. 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. Ultimately, there is no reason to believe that centenarians did not exist in antiquity, even if they were not commonplace.

Research into centenarians

Research in Italy suggests that healthy centenarians have high levels of both vitamin A and vitamin E and that this seems to be important in causing their extreme longevity. Other research contradicts this, however, and has found that this theory does 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, although serum levels of vitamin E were not significantly higher. Researchers in Denmark have also found that centenarians exhibit a high activity of glutathione reductase in red blood cells. In this study, the centenarians having the best cognitive and physical functional capacity tended to have the highest activity of this enzyme.

Other research has found that people whose parents 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 extroverted personalities, according to Thomas T. Perls, the director of the New England Centenarian Study at Boston University. Centenarians will often have many friends, strong ties to relatives and high self-esteem. In addition, some research suggests that the offspring of centenarians are more likely to age in better cardiovascular health than their peers.

DNA repair

Lymphoblastoid cell lines established from blood samples of centenarians have significantly higher activity of the DNA repair protein PARP (Poly ADP ribose polymerase) than cell lines from younger (20 to 70 years old) individuals. The lymphocytic cells of centenarians have characteristics typical of cells from young people, both in their capability of priming the mechanism of repair after H₂O₂ sublethal oxidative DNA damage and in their PARP capacity. PARP activity measured in the permeabilized mononuclear leukocyte blood cells of thirteen mammalian species correlated with maximum lifespan of the species. These findings suggest that PARP mediated DNA repair activity contributes to the longevity of centenarians, consistent with the DNA damage theory of aging.

Contributing factors

According to John W. Santrock's book A Topical Approach to Life-Span Development, there are five factors that research has suggested 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 married. Also, people who have been through traumatic life events learn to cope better with stress and poverty and are more likely to reach age 100.|

Japanese bio-study

Many experts attribute Japan's high life expectancy to the typical Japanese diet, which is particularly low in refined simple carbohydrates, and to hygienic practices. The number of centenarians in relation to the total population was, in September 2010, 114% higher in Shimane Prefecture than the national average. This ratio was also 92% higher in Okinawa Prefecture. In Okinawa, studies have shown five factors that have contributed to the large number of centenarians in that region:

1. A diet that is heavy on grains, fish, and vegetables and light on meat, eggs, and dairy products.
2. Low-stress lifestyles, which are proven significantly less stressful than that of the mainland inhabitants of Japan.
3. A caring community, where older adults are not isolated and are taken better care of.
4. 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.
5. 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.

A historical study from Korea found that male eunuchs in the royal court had a centenarian rate of over 3%, and that eunuchs lived on average 14 to 19 years longer than uncastrated men.

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, Sogen Kato, 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 found that at least 200 other Japanese centenarians were "missing", and began a nationwide search in early August 2010. This incident led to 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, the remains of a mother thought to be 104 had been stuffed into her son's backpack for nearly a decade; in another, a man received around 9.5 million yen (87739USD) in pension payments despite his wife having died six years previously.

Epigenetic studies

By measuring the biological age of various tissues from centenarians, researchers may be able to identify tissues that are protected from aging effects. According to a study of 30 different body parts from centenarians and younger controls, the cerebellum is the youngest brain region (and probably body part) in centenarians (about 15 years younger than expected ) according to an epigenetic biomarker of tissue age known as epigenetic clock. These findings could explain why the cerebellum exhibits fewer neuropathological hallmarks of age related dementias compared to other brain regions. Further, the offspring of semi-supercentenarians (subjects who reached an age of 105–109 years) have a lower epigenetic age than age-matched controls (age difference=5.1 years in peripheral blood mononuclear cells) and centenarians are younger (8.6 years) than expected based on their chronological age.