The Mountain of Youth: What We Can Learn from Okinawa, Japan

JOCELYN CATENACCI

The elderly population of Okinawa, Japan has gained worldwide recognition for enjoying exceptionally long lives with autonomy even into advanced age. This phenomenon has inspired many researchers seeking to unlock the secrets of healthy aging. There is a stone in Ogimi – the poorest and healthiest village in Okinawa – that has a passage inscribed in it that reads, “At 80 you are still a child, if at 90 heaven calls, say ‘Go away!’ and come back when I am 100.” When a researcher interviewed one such centenarian, they said that they wanted to live another 20 years and that “life is beautiful.” It appears the Okinawan population has not only mastered lifespan maximization, but also life satisfaction even in advanced age.

Okinawa is a chain of 169 islands in southwest Japan that stretches between the Japanese mainland and Taiwan (2). It has a population of approximately 1.4 million and is sub-tropical and partially mountainous (3). It is the southernmost prefecture of Japan, and has gained international recognition for having the highest prevalence of centenarians (people aged 100 years or over) in the world. The average prevalence of centenarians in high-income countries is approximately 10-20 per 100,000, whereas in Okinawa the prevalence of centenarians is 40-50 per 100,000 (4). In 2004, the average life expectancy at birth (LEB) was 81.8 years for Okinawa, 81.2 years in Japan as a whole and five years less in the United States at 76.8 years (5). The life expectancy in Japan overall is the highest in the world, and the Japanese prefecture of Okinawa ranks first for not only life expectancy, but also quality of life.

The World Health Organization has stated that Japan is already “leading the world in terms of healthy (disability-free) life expectancy” with Okinawa being its greatest success (6). Even the ‘oldest old’ in Okinawa maintain an unprecedented level of autonomy and physical functionality when compared to a similar age cohort in most other high-income countries. This functionality was measured by their ability to independently complete “activities of daily living” (ADLs) such as bathing and dressing oneself and through the preservation of cognitive capabilities. It is also common for the oldest old of Okinawa to partake in long of hours of field labour every day, and historically, most have enjoyed spending an exceptional 97% of their lives disability-free. Inspired by these observed changes in lifestyle, this article aims to further explore the determinants of longevity in Okinawa–specifically environmental factors (7).

Okinawa is the lowest socio-economically ranked prefecture, with the lowest income per capita in Japan and the lowest physician-to-resident-rate in Japan, which disproves theories that the Okinawan phenomenon only occurred because of economic advantage and the availability of medical care. Okinawans were also greatly discriminated against and disenfranchised in many ways as compared to the rest of Japan. Mainland Japanese feel superior to Okinawans, perceiving them as ‘barely Japanese’, due to the complex Okinawan history, isolated geography and diverse cultures (8).

Though Okinawa has produced hundreds of functional centenarians over the last several decades, it appears that the future generations of Okinawans may not be able to enjoy the same advantages due to the lowering LEB. This exceptional longevity in Okinawa may be a phenomenon of the past. This has been attributed to lifestyle changes brought about by the ‘westernization’ of Japanese culture. The ‘westernization’ of the Okinawan diet involves the increase of protein and saturated fat and decrease in fish-consumption in their diet, resulting in the increase of the fat to energy ratio which has dramatically impacted the expected lifespan of the next generation of Okinawans (those born after WW2) (9).

This makes one wonder what we can  learn from this Japanese minority that has seemingly not only extended life but also youth?

 

OKINAWA CENTENARIAN STUDY

The Okinawa Centenarian Study, initiated in 1976, is an ongoing, population-based study being conducted by Japan’s Ministry of Health (10). Since its inception, it has collected data from over 900 Okinawan centenarians through questionnaires and full geriatric physical and mental assessments.

The results of this ongoing study include the superior physical and cognitive functioning of the Okinawan centenarians, in comparison to non-Okinawan centenarians. Cognitive and physical capacity  was measured through activities of daily living (ADLs) and range of motion as well as self-expression and comprehension of conversation, respectively. In terms of sensory functioning (auditory and visual functioning), Okinawan seniors were adequate, which is impressive considering their greatly advanced age. It is because of their superior physical and mental functioning that it is rare to see a bedridden centenarian in Okinawa. Indeed, all subjects studied could independently ambulate.

The Okinawa Centenarian Study, provided preliminary hypotheses to explain the longevity of the population and  sparked the interest of researchers to delve deeper into the roots of this phenomenon.

VALIDATION

Before we can explore further why the Okinawan population lives such long and healthy lives, one might ask the question – how do we know they are, in fact, as old as they say? Was there an accurate and comprehensive registration system in place in Japan old enough to provide birth information about centenarians (or any registration system, for that matter)? The answer is: Yes! The age claims made by the Okinawan centenarians were validated by the Japanese koseki registration system which was a centralized birth registration system that was established in 1872 (11). In terms of accuracy, the koseki records have been validated by the Japanese Annual Centenarian Report and other reputable organizations with few discrepancies found not to involve age-overestimation, but age-underestimation. In other words, some of the subjects were even older than previously believed.

SIGNIFICANCE

The study of this population is significant because ‘the oldest old’ are the fastest growing age cohort in North America and many other high-income regions. Determining how to reach age 100 and still be autonomous is of great interest and has inspired much scholarship and research. Due to the disproportionate consumption of health resources by citizens 65 years and above, prolonged health and disability-free life may have positive economic implications.

Another reason that the Okinawan centenarians are of great interest is because they represent  an anomaly within the widely accepted Social Gradient Theory which states that the higher the social rank, the longer a person’s lifespan (12). This idea was derived from the Whitehall studies conducted by Marmot et al. on civil servants in Britain from 1967-1977 (13). Less political power, higher unemployment and lower income per capita collectively cause Okinawa to be the poorest prefecture in Japan.

Okinawa’s centenarians are also an anomaly due to Okinawa’s economically poor, uneducated and marginalized population that produced better longevity results than wealthier prefectures. Due to a complicated history between China and Japan with Okinawa being between them both, it has faced great oppression for the past hundreds of years. Japanese mainlanders feel a superiority over Okinawans who are considered to be their “second-class country cousins” (14). Key differences in the culture of mainland Japan and Okinawa such as diet, language and attire also didn’t help the discrimination. Okinawans and mainland Japanese people rarely intermarried even after World War 2 when the prejudice did improve, but even today Okinawans aren’t seen as “fully Japanese” in the eyes of the Japanese mainland population (15). This produced a geographically isolated subculture resistant to assimilation with Japanese culture.

It is for this reason that determining the environmental factors that delay disease, disability, and death, is of great significance and requires further study.

 

FINDINGS

Though much study is still needed, certain characteristics of this population have been discovered.

The representative phenotype of an Okinawan is maintained short stature, low weight and low body-mass-index (BMI) throughout their lives (16). This population exhibited a significantly lower rate of “age-associated diseases” like cardiovascular disease (CVD), stroke and cancer (especially hormone-based) – the leading causes of death in North America – when compared with their Japanese and North American counterparts (17).

Further research has revealed through autopsies that at the time of death, Okinawan centenarians were free of common age-associated diseases like coronary heart disease (CHD), atrophic gastritis, kidney disease, hypertension, and metabolic syndrome (18). Furthermore, Alzheimer’s and other neurodegenerative disorders are unheard of in Okinawa (19).

The most common cause of death in Okinawa is infectious disease, such as pneumonia, rather than the aforementioned chronic diseases that plague the elderly populations of most high-income countries.

Studies have shown that when Okinawans migrate, their health and longevity resembles that of their new population.

PHYSICAL ACTIVITY

Elderly Okinawans (age 75 and over) on average spend 9-12 hours a day doing labour-intensive work such as farming, plowing, and even climbing up trees to retrieve fruit and showed no signs of slowing down (20). Based on numerous interviews, elderly Okinawans, could not imagine not working the majority of the day and attribute their health to enjoying their work. There isn’t even a word for “retirement” in most Okinawan dialects.

Other than participating in physical activity for their work, Okinawans also engage in group exercise frequently as this kind of social gathering is important in their culture. An example of this would be karate which was invented in Okinawa.

TRADITIONAL DIET

The characteristics of the traditional Okinawan diet and culture that have been proven to aid in longevity are the caloric restriction and the nutrient-rich native foods (such as sweet potatoes, goya and konbu) which proves to be a cultural diet highly cardio-protective and anti-hypertensive (21).

Mild long-term caloric restriction (calorie deficit), was highly prevalent in this population and was beneficial to health (22). Mild caloric restriction results in a negative energy balance due to fewer calories consumed as well as  lowered insulin concentration and body temperature, both of which are known biomarkers of increased lifespan. Okinawans consume 83% of the average national intake, perhaps inspired by the traditional Okinawan rule of eating until one is 80% full (23).

The traditional Okinawan diet is low in fat, high in carbohydrates and 96% plant-based. The main foods that make up the traditional Okinawan diet are fish, soy, green vegetables, sweet potatoes, pork, seaweed, goya (bitter Okinawan melon) and tomatoes. In terms of drinking, Okinawans consume unsweetened green tea every day. These foods with green tea are high in phytonutrients, and most contain anti-oxidants and flavonoids that help prevent chronic disease by ‘quenching’ free radicals that would otherwise cause oxidative damage and inflammation in the body.

Sweet potatoes, for example, are the staple carbohydrate in the Okinawan diet and are credited with greatly enhancing their health due to the abundance of dietary fiber, natural sugars and vitamins in them (24). They are also extremely beta-carotene dense, which prevents free radical-caused damage, slowing the aging process. On the mainland, however, rice is more expensive and preferred over sweet potatoes which is associated with lower social rank (25). Interestingly, this means that the less costly and less prestigious alternative was, in fact, the healthier one.

Also, seaweed, or konbu, is frequently found in Okinawan food, and is known to help prevent arthritis and reduce oxidative stress in the body. Goya, a bitter Okinawan melon, is also a staple in the Okinawan diet that is commonly used as a medicinal herb as well.

On average, Okinawans consume 80% less salt than the national average due to their fruit and vegetable-rich diet of the “functional foods” they harvest (26). Meat and refined grain consumption is much lower in Okinawa than the national average along with saturated fat, sugar and salt.

The traditional Okinawan diet with its low-fat and high-carbohydrate properties is very similar to the “Mediterranean diet” and the “Dietary Approaches to Stop Hypertensive” (DASH) diet although one key difference that sets the Okinawan diet apart from these is that it is cultural.

SOCIAL CULTURE

Okinawans have a very community-focused, low-stress culture with the vast majority of the population being native-born (27). Okinawans tend to live either with or close to their family and participate in daily familial activities together. This family-oriented culture has greatly contributed to the prosperous lives in this subculture due to their being a lack of apathy and social isolation (28).

Although Okinawans are ranked low within the national Japanese social hierarchy, there is a lack of social hierarchy within Okinawa itself. Women in Okinawa are revered as spiritual leaders, and in their culture, respect increases with age, unlike North America where abuse of the elderly occurs. Despite examples of ageism in many high-income countries, many Okinawans value their own disability-free longevity as respect in Okinawa increases with age.  Also, Okinawans practice ancestor worship which shows a respect for history and past generations which helps them form a sense of identity, ethnic self-esteem, belonging and great kinship networks (29).

Okinawans claim that all of these social aspects of their culture help reduce stress, therefore having a buffering effect on this population’s health, improving the resilience of their immune systems. Some potential negative health consequences of prolonged stress include depression, anxiety, arthritis, cancer, asthma and many other stress-induced illnesses (30). The Okinawan culture focuses on achieving a minimal stress environment and succeeds with drastically lower average stress levels compared to those living in metropolitan areas of Japan and their international counterparts.

CONCLUSION

In conclusion, there is a lot to be learned from the case of the Okinawan centenarians that can aid in not only extending lifespan and functionality but also maintaining a positive outlook even in advanced age. The characteristic intensity of elderly physical activity, native antihypertensive diet and stress-minimizing culture are the keys to the longevity of the Okinawans. It is through these environmental conditions that this subpopulation has achieved such lauded prosperity. It is also an anomaly to the widely accepted Social Gradient Theory because it maintains excellent health despite being a low-income and socially-marginalized prefecture.

What North Americans, especially, should take away from the Okinawa centenarians is that they not only had a highly active lifestyle with a highly nutritious diet but also their values. In all the research conducted, there was never a mention of money, prestige or competition amongst this population. They valued family, hard work and living simply as well as having a profound respect for their elderly population and the generations that had preceded them. The Okinawans prove that North American culture has much to want for. It is through these cultural values that they have managed to achieve a seemingly uncomplicated prosperity.

Though studies have been conducted on this population, such as the OCS, there is still inadequate research to fully understand such a complex concept as longevity.

It is through emulating the Okinawan culture that we can have a profound impact not only on our long-term health but also on our economy through a lessened burden of disease. The traditional Okinawan culture, therefore, seems to be the key the world can use to unlock possibilities for the optimization of not just health, but also youth.

References

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(3): Cockerham, W.C., & Yamori, Y. Okinawa: an exception to the social gradient of life expectancy in Japan. Asia Pacific J. Clin Nutr.  10(2), 155 (2001).

(4): Willcox, D. C., Willcox, B. J., Hsueh, W. C., & Suzuki, M. Genetic determinants of exceptional human longevity: insights from the Okinawa Centenarian Study. Age. 28(4), 313 (2006).

(5): Bernstein, A. M., Willcox, B. J., Tamaki, H., Kunishima, N., Suzuki, M., Craig Willcox, et al. First autopsy study of an Okinawan centenarian: absence of many age-related diseases. J. Geronto Ser A: Bio Sci and Medl Sci59(11), 1195 (2004).
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(15): Cockerham, W.C., & Yamori, Y. Okinawa: an exception to the social gradient of life expectancy in Japan. Asia Pacific J. Clin Nutr.  10(2), 155 (2001).

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(28): Chan, Y. C., Suzuki, M., & Yamamoto, S. Dietary, anthropometric, hematological and biochemical assessment of the nutritional status of centenarians and elderly people in Okinawa, Japan. J. Am Col Nutr16(3), 233 (1997).

(29): Cockerham, W.C., & Yamori, Y. Okinawa: an exception to the social gradient of life expectancy in Japan. Asia Pacific J. Clin Nutr.  10(2), 154-158 (2001).

(30): Park, J., Kitayama, S., Karasawa, M., Curhan, K., Markus, H. R., Kawakami et al. Clarifying the links between social support and health: Culture, stress, and neuroticism matter. J. Health Psych18(2), 226-235 (2013).

 

 

 

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