An Emerging Longevity Blue Zone in Sicily: The Case of Caltabellotta and the Sicani Mountains
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe goal of this paper is to demonstrate that a particular part of Sicily is an emerging “Blue Zone” (BZ). It does so in a scholarly way using recognized methods. It is, however, only original in the sense that it looks at a region that heretofore has not been considered a BZ. It does not, however, advance theory or methodology. The authors need to provide a stronger argument beyond its empirical uniqueness for its originality.
The authors end section 4.4 by suggesting that BZs need to be “cultivated.” They do not, however, provide a convincing argument as to why BZs need to be cultivated or for that matter why they are important theoretically in advancing our understanding of longevity or for the development of broader population policies. Are there inherent properties or lessons of BZs that might be translated into policies that can be replicated in areas that do not have the same unique environmental properties of BZs or used to replicate some of the lifestyle factors associated with BZs?
The other section of the paper that requires substantial improvement is the discussion of the limitations. First and foremost, more critical discussion of the arbitrary definition of BZ is required. The fact that the study area in Sicily matches many of the characteristics of Sardinia as a BZ is not a justification to ignore the limitations of the definition of BZs altogether. A second improvement required is a more nuanced discussion of the migration of people out of the study region. The authors only discuss the possibility that they undercount the number of people 90+ and centenarians, but what if out-migrants are disproportionately those who might have died before they were 90? Would the study area still be considered a BZ? A third improvement is to acknowledge that the discussion of factors that “explain” longevity in the study area is correlational. Only future studies that focus on individuals 90+ and their actual behaviors and exposures to environmental factors might explain their longevity is required in conjunction with those who have left the region. Such a study might be practically impossible to carry out, but this does not mean this limitation should be ignored.
Author Response
Comment 1: The goal of this paper is to demonstrate that a particular part of Sicily is an emerging “Blue Zone” (BZ). It does so in a scholarly way using recognized methods. It is, however, only original in the sense that it looks at a region that heretofore has not been considered a BZ. It does not, however, advance theory or methodology. The authors need to provide a stronger argument beyond its empirical uniqueness for its originality.
Response 1: We thank the reviewer for this important observation. While we recognize that the methodological approaches used in our study are well-established, we believe the originality of our work extends beyond the empirical analysis of a previously unexamined region. Specifically, we introduce the novel concept of dynamic Blue Zones, which can both “emerge” and “disappear” over time, acknowledging that some historically designated Blue Zones have undergone demographic shifts that undermine their once-exceptional status (such as Okinawa, PMID: 38221516). By conceptualizing Blue Zones as dynamic rather than static systems, our study contributes a theoretical reframing that has implications for both demographic research and health policy. This perspective encourages a more nuanced understanding of longevity hotspots as evolving phenomena, subject to social, environmental, and temporal influences.
Comment 2: The authors end section 4.4 by suggesting that BZs need to be “cultivated.” They do not, however, provide a convincing argument as to why BZs need to be cultivated or for that matter why they are important theoretically in advancing our understanding of longevity or for the development of broader population policies. Are there inherent properties or lessons of BZs that might be translated into policies that can be replicated in areas that do not have the same unique environmental properties of BZs or used to replicate some of the lifestyle factors associated with BZs?
Response 2: We appreciate this insightful critique. In the revised version, we have strengthened the argument in Section 4.4 by drawing on theoretical frameworks from population health and sustainability studies. We argue that BZs represent rare, complex systems where beneficial cultural, environmental, and lifestyle factors converge, and that their persistence requires intentional preservation, outweighing modernizing pressures. We also expand on how certain elements, such as diet, physical activity, and social structures, might be translated into public health interventions in non-BZ settings, even where environmental conditions cannot be replicated. We added the following paragraph “Blue Zones can be understood as emergent, ecologically embedded systems where biological, behavioural, and sociocultural factors interact synergistically to promote healthy aging [2,68]. These regions offer natural experiments in longevity, aligning with ecological models of health that emphasize multilevel determinants, from individual behaviours to environmental and community contexts [69]. The cultivation of BZs is critical not only for preserving these unique demographic phenomena in the face of globalization and modernization [70], but also for extracting transferable lessons for broader population health strategies. For example, the study of geophysical and environmental factors is often overlooked in longevity research [71], yet it has a significant impact on numerous physiological processes in humans and has shown replicable health benefits in diverse settings [72]. Thus, BZs serve both as theoretical models of healthy longevity and as empirical sources for shaping health-promoting policies that respect cultural and environmental contexts, such as reducing pollution and expanding green spaces, and fostering socialization and community bonds.” as well as five more citations (page 13, lines 527-540).
Comment 3: The other section of the paper that requires substantial improvement is the discussion of the limitations. First and foremost, more critical discussion of the arbitrary definition of BZ is required. The fact that the study area in Sicily matches many of the characteristics of Sardinia as a BZ is not a justification to ignore the limitations of the definition of BZs altogether.
Response 3: We concur and have revised Section 4.5 to more explicitly address the conceptual ambiguity surrounding Blue Zone definitions. Currently, there is considerable disagreement among scholars regarding how a Blue Zone should be defined. One plausible assumption is that the longevity of a given region can be defined as "exceptional" only if the corresponding longevity index exceeds the lower confidence limits of the distribution measured in the less long-lived surrounding areas. In our case, the 90+/60+ ratio in Caltabellotta exceeded the 99th percentile of the 90+/60+ ratio distribution in Sicily's 391 municipalities. In this statistical sense, the longevity of this community can already be considered exceptional. However, we adopted an even more stringent criterion, comparing Caltabellotta longevity with that of a Blue Zone in Sardinia, which has already been certified. Anyway, we acknowledge that the BZ label is partly heuristic and that caution is warranted in its application. Our intent is not to claim definitive BZ status for Caltabellotta, but to argue that its characteristics warrant continued study as a “potentially emerging” example. We added the sentence “Currently, there is considerable scholarly debate regarding the appropriate criteria for defining a Blue Zone. A defensible assumption is that a region longevity can be considered “exceptional” when its longevity index exceeds the lower confidence bounds of the distribution observed in less long-lived surrounding areas. In our analysis, the 90+/60+ ratio in Caltabellotta exceeded the 99th percentile of the same index across all 391 municipalities in Sicily. Statistically, this suggests that Caltabellotta longevity profile is already exceptional. Nonetheless, we adopted a more rigorous benchmark by comparing Caltabellotta to a recognized Blue Zone in Sardinia. We also acknowledge that the Blue Zone designation remains partly heuristic and should be applied with appropriate caution. Our aim is not to assert definitive Blue Zone status for Caltabellotta, but rather to argue that its demographic characteristics merit further investigation as a potentially emerging Blue Zone.” (page 9, lines 302-312).
Comment 4: A second improvement required is a more nuanced discussion of the migration of people out of the study region. The authors only discuss the possibility that they undercount the number of people 90+ and centenarians, but what if out-migrants are disproportionately those who might have died before they were 90? Would the study area still be considered a BZ?
Response 4: This important point has been addressed in Section 4.5. Migration dynamics are critical to interpreting longevity trends, especially in rural areas with known out-migration. In this line, our approach was designed to minimize the impact of migration on assessing longevity. Our calculation was based on the proportion of a given birth cohort that had reached the threshold age of 90 or 100 years, not on the proportion of nonagenarians or centenarians in the total resident population. In this case, both the numerator (those reaching age 90+) and the denominator (births) are based on place of birth. Consequently, migration which selectively remove less healthy individuals who might not have reached advanced ages, cannot increase the calculated index, only decrease it. Therefore, our estimate is conservative and robust, strengthening the credibility of the observed longevity pattern in Caltabellotta. Since the value detected in Caltabellotta already reaches the minimum threshold that characterizes a Blue Zone, our estimate of longevity in the village can, at most, be lower than the real one. A more accurate estimate of longevity in the target area would require longitudinal, individual-level data, which are not presently available. We added the following sentence in the revised manuscript and cited our methodological 2013 article in support “Moreover, the study minimized migration bias by measuring longevity using birth cohorts, specifically, the proportion of people born in the area who reached age 90 or 100. Both numerator and denominator were based on place of birth, avoiding distortions from population movement. Since births in a geographic area are fixed, this method offers a conservative and reliable estimate. Any migration would likely lead to under-estimation, not overestimation of longevity, reinforcing the credibility of the results observed in the target area.” (page 14, lines 546-552).
Comment 5: A third improvement is to acknowledge that the discussion of factors that “explain” longevity in the study area is correlational. Only future studies that focus on individuals 90+ and their actual behaviors and exposures to environmental factors might explain their longevity is required in conjunction with those who have left the region. Such a study might be practically impossible to carry out, but this does not mean this limitation should be ignored.
Response 5: We fully agree. In the revised manuscript, among the limitations we more explicitly state that the lifestyle and environmental correlates presented are based on indirect, ecological evidence and are therefore hypothesis-generating rather than explanatory. We underscore the need for future individual-level studies incorporating dietary recall, physical activity monitoring, and in-depth interviews with long-lived individuals and their families, as well as migrants, to validate these associations. These clarifications have been added to the Discussion as follows “Finally, the factors put in relation with longevity in the study area are only correlational. Only future studies comparing behaviours and exposures to environmental factors between individuals 90+ and those who have left the region might give better insight into the longevity of this community. In particular no interviews or direct observational data were collected, and as such, more research will be necessary to gain a deeper understanding of the hypothesized links between environmental, lifestyle, and social factors and the exceptional longevity observed in the Sicani Mountains.” (page 12, lines 515-518).
Reviewer 2 Report
Comments and Suggestions for Authorsmanuscipt focused on healthy aging. Aging is an importnat subject in current century.
some suggestion to improve and to become more understandable the munscript
- More Explanation about BZ in world with statistical details to familiarity readers with BZ in worlds specially in Europe countries.
- Moran index is between -1 to +1, from dispersion to cluster. Zero value in Moran index shows random pattern. Suggest to write Moran index with 0.00 ( 2 decimal).
- Getis index use to show spatial pattern of distribution. It is better to add Getis Ord maps in article.
- To familiarity readers with case study region, suggest add an mid or high resulotion RS image to article.
- life style analysis need to interview data from diet, activity and etc. The munscript used only organizational data and suggest findings limit to used database.
- cunclusion is short and suggest to improve and develope.
Author Response
Comment 1: manuscipt focused on healthy aging. Aging is an importnat subject in current century.
some suggestion to improve and to become more understandable the munscript
More Explanation about BZ in world with statistical details to familiarity readers with BZ in worlds specially in Europe countries.
Response 1 Thank you for this suggestion. We have expanded the Introduction to include more detailed statistics on established Blue Zones worldwide, with particular emphasis on European regions. Comparative figures for the prevalence of centenarians and nonagenarians have been added to contextualize the findings from Sicily. We added the following paragraph “For example, Okinawa’s 1975 census recorded 37 centenarians in a population of 1.04 million (35.5 per million), roughly seven times the Japanese average of 5.1 per million [8]. the number of newborns reaching age 90 per 100,000 in the Sardinia BZ is 12,575 and 12,729 among men and women, respectively versus 3506 and 8745 in mainland It-aly [9]. Other Blue Zones: Nicoya (Costa Rica) and Ikaria (Greece) are similarly noted for longevity. Nicoya men especially live far longer than average, and Ikaria has one of the world’s lowest rates of middle-age mortality [7]. Across Europe, high longevity is concentrated in Mediterranean countries. France, Italy, and Greece each had over 20 centenarians per 100,000 inhabitants in 2011. These statistics underscore that Mediterranean communities support much higher proportions of very old individuals than national averages. Collectively, the data illustrate that Blue Zone areas in Europe and around the world host an unusually large share of the oldest-old, highlighting the role of environmental and lifestyle factors in healthy aging” (page 2, lines 48-60)
Comment 2: Moran index is between -1 to +1, from dispersion to cluster. Zero value in Moran index shows random pattern. Suggest to write Moran index with 0.00 ( 2 decimal).
Response 2: We have revised the text and figures to report Moran’s I index with two decimal places, consistent with standard spatial analysis conventions. We thank the reviewer for this technical correction.
Comment 3: Getis index use to show spatial pattern of distribution. It is better to add Getis Ord maps in article.
Response 3: We agree this would enhance clarity. We have now replaced Figure 1b with the Getis-Ord Gi* Z-score maps to visualize statistically significant positive and negative hot spots of longevity, complementing the hot-spots analysis (page 6, figure 1d).
Comment 4: To familiarity readers with case study region, suggest add an mid or high resulotion RS image
Response 4: We appreciate this idea. A high-resolution satellite image of the study region (Caltabellotta and surrounding Sicani Mountains) has now been included as Figure 1b, annotated to indicate key topographical features (Page 6, figure 1b).
Comment 5: life style analysis need to interview data from diet, activity and etc. The munscript used only organizational data and suggest findings limit to used database.
Response 5: We acknowledge this limitation and have revised the language throughout the Discussion to clarify that our findings on diet, physical activity, and social cohesion are based on indirect indicators and historical data. Regarding the need for interview-based insights, we noted that two previous studies on longevity in the Sicani Mountains, cited in our manuscript (PMID: 22524271; PMID: 22533429), included interviews with older individuals in the region. Building on this foundation, future research could expand the scope of qualitative inquiry to explore additional dimensions. We have added the following sentence to underscore this point: “In particular, no interviews or direct observational data were collected, and as such, more research will be necessary to gain a deeper understanding of the hypothesized links between environmental, lifestyle, and social factors and the exceptional longevity observed in the Sicani Mountains” (page 14, lines 556–559).
Comment 6: cunclusion is short and suggest to improve and develope.
Response 6: The Conclusion section has been expanded to better synthesize key findings and to more clearly articulate the broader implications for future research and public health planning. We now emphasize the dynamic concept of “emerging” Blue Zones and the importance of early identification for both scientific inquiry and policy design. We added “Together, these findings synthesize our key results and suggest meaningful directions for research and policy. For researchers, the results motivate deeper, multidisciplinary studies – for example, longitudinal and molecular work – to disentangle the roles of diet, activity, community, and possibly genetics in driving the observed healthy ageing. For public health planners, they imply that fostering Blue Zone–like environments (through community design, nutritional guidance, and social support) could extend healthy lifespan at the population level. Indeed, recent Blue Zones initiatives – which translate these lifestyle principles into community policies – have demonstrably in-creased life expectancy and reduced chronic disease in trial cities. Finally, our work highlights the dynamic nature of longevity clusters: as lifestyle and demography change, new Blue Zones may emerge. Early identification of such zones is therefore valuable, since it allows public health systems to learn from and perhaps encourage the beneficial practices that underlie exceptional longevity. Further research will be necessary to gain a deeper understanding of the hypothesized links between environ-mental, lifestyle, and social factors and the exceptional longevity observed in the Sica-ni Mountains.” (pages 14-15, lines 584-598).
Round 2
Reviewer 2 Report
Comments and Suggestions for AuthorsThe requested corrections have been made. The submitted file is a track version.