The Science Behind Blue Zones: Demographers Debunk the Critics

We are career demographers, epidemiologists, geriatricians, and other scientists with expertise in the study of aging, who have identified and extensively studied the world’s longevity “hot spots,” often referred to as “blue zones.” We are writing to object to Saul Newman’s academically misleading and deeply flawed preprint paper, which has not yet been published in a peer-reviewed scientific journal, despite having been submitted for publication over four years ago. Furthermore, Saul Newman is a plant biologist with no academic training or expertise in demography, gerontology, or geriatrics, and has no record of publication in these fields of study.

Below, we have provided links to some of our peer-reviewed academic papers, which thoroughly detail how we have confirmed the ages of centenarians and older individuals in each of the blue zones we have studied, along with the statistical methodology used to validate their extraordinary longevity.

What are blue zones?

Blue zones are geographically defined areas with a disproportionately high number of exceptionally aged people, especially nonagenarians and centenarians. These zones first gained international attention two decades ago when the term was introduced in the well-respected, peer-reviewed journal Experimental Gerontology by Dr. Michel Poulain and colleagues. The term later appeared in National Geographic (2). Since then, numerous scientific papers have validated the demographic origins of blue zones and attempted to extract valuable insights from them (3-12). They have been fully validated by strict demographic criteria in four locations thus far: Okinawa, Japan; Sardinia, Italy; Ikaria, Greece; and Nicoya, Costa Rica.

Newman, in his unreviewed preprints (13, 14), omits or misunderstands the rigorous age verification and statistical analysis involved in identifying blue zones. The procedure is highly accurate and includes:

• Identifying potential high-longevity target areas based on reliable public demographic databases, which have low error rates.
• Accurately counting the number of people born in the target area, categorized by sex and year of birth.
• Identifying individuals who have reached a preset threshold age (e.g., 90 years), regardless of residence.

Subsequently, the ratio of long-livers to total births during the same time interval is recorded. This index reflects the probability of individuals born in the target area reaching the threshold age. The methodology considers all individuals born in the target area, whether alive, deceased, or emigrated. The process is designed to minimize the likelihood of false positives (Type I errors) and ensures accurate identification of blue zones.

In addition, we determine age-specific mortality rates of the older population, free of age-exaggeration bias, and estimate remaining life expectancy and probabilities of surviving to become a centenarian.

In Sardinia, for example, we double-checked the age of every centenarian in the blue zone villages using:

• Civil status databases dating back to 1866.
• Handwritten records from ecclesiastical archives, consistently available from the 17th century onward.
• A complete genealogical reconstruction of village inhabitants from 1866 onward.

Not only were the birth and death dates of each centenarian confirmed, but those of their siblings were also cross-checked. This allowed us to rule out any possible identity switches, such as the case of a false supercentenarian that was rigorously eliminated from our Sardinian centenarians’ database (15).

Alternatively, in the Nicoya blue zone, all estimates are based on well-documented birth dates from the civil registration registry established in Costa Rica in 1883, rather than self-reported ages. Individuals not found in the registry (immigrants) or whose birth was recorded later in life were excluded.

Newman’s Critique

Newman’s draft papers, which he is vigorously promoting in the mainstream media, attempt to discredit the blue zones by presenting a series of false equivalencies (13, 14). He argues that the excessive number of centenarians and supercentenarians in non-blue zone areas is due to poor demographic records, which is often the case. However, he ignores the fact that this criticism does not apply to blue zones, where ages have been rigorously validated with modern, accurate demographic methodology.

Newman also alleges that birthdates in blue zones exhibit “age heaping” patterns. However, such patterns do not appear in the validated datasets from blue zones, which show no unusual distribution of birthdates. Furthermore, his examples of fraudulent death registrations in Japan and the U.S. have no bearing on blue zones, as we have meticulously validated all ages before analysis, expunging any such cases from our datasets.

His assertion that blue zones correspond to regions with high illiteracy, poverty, and crime is misleading. While some blue zones experienced delays in economic and social development (16), these factors have no influence on the calculation of longevity rates. For instance, in 2005, Okinawa had the highest centenarian rate from age 70, far surpassing Japanese national averages (17). However, as we have publicly acknowledged, the growth in life expectancy in Okinawa has slowed, particularly in comparison to other prefectures in Japan. There are various factors contributing to this phenomenon, but a social gradient involving high illiteracy, poverty, and crime is not among them (16). Japan is well known for having one of the lowest crime rates in the world. However, the arrival of modern (Western) diets and transportation infrastructure that does not promote walking has led to reduced activity levels, lower energy expenditure, and increasing rates of obesity in Okinawa prefecture (18). Longevity is not a static phenomenon and can change as lifestyle shifts occur within a population. Age validation studies have also been conducted in Okinawa using methods similar to those used in other blue zones, providing strong evidence for the exceptional longevity of the Okinawan blue zone (19).

Newman’s use of Sardinia-wide crime and poverty statistics to generalize about blue zones is also misleading. The Sardinian blue zone is a small rural area of about 50,000 people spread across six mountain villages, whereas Sardinia as a whole has a population of 1.6 million, most of whom live in major urban areas like Sassari and Cagliari.

Conclusion

In conclusion, the ages of individuals in the officially recognized blue zones have been thoroughly validated, and their exceptional longevity is well-documented. Newman’s unreviewed papers are both ethically and academically irresponsible. His promotion of them in the mainstream media is an insult to both the scientific community and the blue zones communities themselves, who take pride in their elders and culture of longevity.

Sincerely,

 

Gianni Pes

Dip. Medicina, Chirurgia e Farmacia, Università di Sassari, Sassari, Italy.

 

Luis Rosero-Bixby

Centro Centroamericano de Población, Universidad de Costa Rica, San José, Costa Rica.

 

Christina Chrysohoou, Christodoulos Stefanadis

First Department of Cardiology, School of Medicine, National and Kapodistrian University of Athens, Hippokration General Hospital, Athens, Greece.

 

Bradley J. Willcox

Department of Geriatric Medicine, John A. Burns School of Medicine, University of Hawaii, Honolulu, HI 96817, USA; Center of Biomedical Research Excellence for Translational Reseach on Aging, Department of Research, Kuakini Medical Center, Honolulu, HI 96817, USA

 

Craig Willcox

Department of Human Welfare, Okinawa International University, Ginowan 901-2701, Japan.

 

 

References:

1. Poulain M, Pes GM, Grasland C et al. Identification of a geographic area characterized by extreme longevity in the Sardinia island: the AKEA study. Exp Gerontol. 2004;39:1423-9.
2. National Geographic, 2005.
3. Appel LJ. Dietary patterns and longevity: expanding the blue zones. Circulation. 2008;118:214-5.
4. Buettner D, Skemp S. Blue Zones: Lessons From the World’s Longest Lived. Am J Lifestyle Med. 2016;10:318-21.
5. Huang Y, Mark Jacquez G. Identification of a Blue Zone in a Typical Chinese Longevity Region. Int J Environ Res Public Health. 2017;14:571.
6. Poulain M, Herm A, Errigo A et al. Specific features of the oldest old from the Longevity Blue Zones in Ikaria and Sardinia. Mech Ageing Dev. 2021;198:111543.
7. Pes GM, Dore MP, Tsofliou F et al. Diet and longevity in the Blue Zones: A set-and-forget issue? Maturitas. 2022;164:31-37.
8. Najafi P, Mohammadi M. Redefining Age-Friendly Neighbourhoods: Translating the Promises of Blue Zones for Contemporary Urban Environments. Int J Environ Res Public Health. 2024;21:365.
9. Rosero-Bixby L, Dow WH, Rehkopf DH. The Nicoya region of Costa Rica: a high longevity island for elderly males. Vienna Yearb Popul Res. 2013;11:109-136.
10. Rehkopf DH, Dow WH, Rosero-Bixby L, Lin J, Epel ES, Blackburn EH. Longer leukocyte telomere length in Costa Rica’s Nicoya Peninsula: a population-based study. Exp Gerontol. 2013;48:1266-73.
11. Azofeifa J, Ruiz-Narváez EA, Leal A, Gerlovin H, Rosero-Bixby L. Amerindian ancestry and extended longevity in Nicoya, Costa Rica. Am J Hum Biol. 2018;30(1).
12. Rosero-Bixby L. The vanishing advantage of longevity in Nicoya, Costa Rica: A cohort shift. Demographic Research. 2023;49:723-36.
13. Newman SJ. Supercentenarians and the oldest-old are concentrated into regions with no birth certificates and short lifespans. bioRxiv, 2019, 704080.
14. Newman SJ. Supercentenarian and remarkable age records exhibit patterns indicative of clerical errors and pension fraud. bioRxiv, 2024, 704080.
15. Poulain M, Pes GM, Carru C et al. The Validation of Exceptional Male Longevity in Sardinia. In: Robine, JM., Crimmins, E.M., Horiuchi, S., Yi, Z. (eds) Human Longevity, Individual Life Duration, and the Growth of the Oldest-Old Population. International Studies in Population, 2007, vol 4. Springer, Dordrecht.
16. Cockerham WC, Hattori H, Yamori Y. The social gradient in life expectancy: the contrary case of Okinawa in Japan. Soc Sci Med. 2000;51:115-22.
17. Robine JM, Herrmann FR, Arai Y et al. Exploring the impact of climate on human longevity. Exp Gerontol. 2012;47:660-71.
18. Willcox BJ, Willcox DC, Todoriki H, et al. Caloric restriction, the traditional Okinawan diet, and healthy aging: the diet of the world’s longest-lived people and its potential impact on morbidity and life span. Ann N Y Acad Sci. 2007 Oct;1114:434-55.
19. Willcox DC, Willcox BJ, He Q, et al. They Really Are That Old: A Validation Study of Centenarian Prevalence in Okinawa, J Gerontol A Biol Sci Med Sci. 2008;63(4):338-49.