Currently, serious problems associated with environmental pollution are observed all over the world, especially in developing countries, which manifests itself in the form of a negative impact of environmental factors on the health of the population as a whole, especially on the health of the younger generation. Epidemiological studies conducted in Organisation for Economic Co-operation and Development countries have established indisputable evidence that there is a reliable link between environmental pollution and morbidity and mortality from neoplasms and respiratory diseases. At the same time, there is no reliable data on the role of environmental factors in the development of chronic diseases in children and adolescents, including the study of the interaction between chemical, social, behavioral factors and the gene pool with the environment. That is, these studies had some limitations in studying the epidemiology of chronic diseases and environmental stress factors.

Background: Circulating α-Klotho is a longevity-related protein with anti-inflammatory and cytoprotective functions. Evidence on its relationship with individual leukocyte populations is limited, while eosinophils may have both inflammatory and tissue-homeostatic roles. We examined the association of serum α-Klotho with absolute and relative eosinophil measures in older adults. Methods: This cross-sectional analysis included 502 community-dwelling adults aged ≥60 years with serum α-Klotho data; 493 also had a complete blood count with differential. α-Klotho was analyzed continuously because no universally accepted clinical reference interval or diagnostic cut-point exists. The primary analysis assessed the Spearman correlation between α-Klotho and absolute eosinophil count; eosinophil percentage and the eosinophil-to-lymphocyte ratio were supportive measures. Robust linear regression estimated the percentage difference in α-Klotho per 1-standard-deviation increase in log-eosinophil count after adjustment for demographic, renal, hematological, smoking, and respiratory factors. Results: The median serum α-Klotho concentration was 1354.99 pg/mL (interquartile range 979.54-4047.59), and the median absolute eosinophil count was 0.14 ×10⁹/L (0.09-0.20). α-Klotho correlated positively with absolute eosinophils (Spearman ρ = 0.175; false-discovery-rate-adjusted q = 0.001), eosinophil percentage (ρ = 0.152; q = 0.004), and the eosinophil-to-lymphocyte ratio (ρ = 0.139; q = 0.008). In the fully adjusted model (n = 479), each 1-standard-deviation increase in log-eosinophils was associated with 22.3% higher α-Klotho (95% confidence interval 9.1-37.0%; p < 0.001). The association persisted after restricting α-Klotho to its 1st-99th percentiles (16.9% higher; 95% confidence interval 4.6-30.7%; p = 0.006) and after adjustment for study centre. Conclusion: Higher circulating α-Klotho was independently associated with higher absolute and relative eosinophil measures in this older Central Asian cohort. The direction differs from some population-based reports and should be considered hypothesis-generating. Prospective studies with eosinophil phenotyping, allergy and parasite assessment, and standardized α-Klotho assays are needed before the finding can be interpreted in relation to healthy longevity.

Background: The relation of circulating α-Klotho to individual leukocyte populations is uncertain. An exploratory 13-marker hematological screen identified eosinophils as a candidate signal, motivating this focused analysis. Methods: The grant-funded α-Klotho substudy included 504 assayed serum specimens. After excluding one participant aged < 60 years and one with missing age, 502 participants were eligible. α-Klotho was measured with the FineTest Human SAKL ELISA kit (EH4278; calibration range 93.75–6000 pg/mL). Because results above the upper calibrator had been software-extrapolated without repeat dilution, the primary analysis was restricted to 397 participants with reported concentrations ≤ 6000 pg/mL; 388 had an eosinophil count. Spearman’s correlations were corrected across 13 hematological markers using Benjamini–Hochberg adjustment. Ordinary least-squares models used HC3 heteroskedasticity-consistent standard errors. Results: Median α-Klotho in the primary cohort was 1179.67 pg/mL (IQR 920.07–1686.51). Absolute eosinophil count correlated weakly with α-Klotho (ρ = 0.120; p = 0.018), but the association did not survive correction across the screening family (q = 0.146). In the fully adjusted model (n = 376), each 1 SD higher log-eosinophil count was associated with 8.4% higher α-Klotho (95% CI 2.0–15.2%; p = 0.009). The quartile trend was significant (p = 0.019), whereas median regression produced a smaller estimate (5.4%; bootstrap 95% CI −0.6 to 12.5%). Estimates were similar after recruitment-stratum adjustment and after excluding eosinophilia, chronic respiratory disease, or leukocyte counts > 15 × 10⁹/L. Conclusions: Within the assay calibration range, higher eosinophil counts were associated with modestly higher serum α-Klotho after adjustment for measured covariates. The post hoc origin, assay limitations, and cross-sectional design make this a hypothesis-generating immune association rather than evidence of causality, healthy longevity, or a clinical threshold.