Epidemiological support for a multifactorial aetiology of Kashin-Beck disease in Tibet

Abstract

We carried out a cross-sectional study in 12 rural villages in order to identify the risk factors for Kashin-Beck disease in Tibet. Children aged 5-15 years (n=575) were examined and their corresponding houses were visited. Samples were collected in order to study fungal contamination of stored grain and the organic matter content of drinking water. Multivariate analysis was performed using logistic regression and population attributable fractions were computed to estimate the impact of each factor. The following variables were independently associated with the disease: age, gender, low socio-economic status, indicators of a poorly diversified diet, iodine deficiency and small water container size (with higher organic matter levels in small containers). Selenium deficiency was severe in all study subjects. The degree of fungal contamination of barley grain was related to the highest percentage of cases (65%) in a sample of the study population. Higher urinary iodine levels were not associated with decreasing prevalence rates when Alternaria sp. was isolated. The data that we report supports the hypothesis that Kashin-Beck disease occurs as a consequence of oxidative damage to cartilage and bone cells when associated with decreased antioxidant defence. Another mechanism that may coexist is bone remodelling stimulated by thyroid hormones whose actions can be blocked by certain mycotoxins.Résumé Nous avons réalisé une enquête transversale dans 12 villages ruraux afin d'identifier les facteurs de risque de la maladie de Kashin-Beck au Tibet. Les enfants âgés de 5 à 15 ans (n=575) et leurs maisons ont été examinés. La contamination fongique des céréales et le contenu en matières organiques de l'eau de boisson ont été étudiés dans des échantillons de la même population. L'analyse multivariée a été effectuée par régression logistique et les fractions attribuables ont été calculées afin d'estimer l'impact de chaque facteur. Les variables suivantes étaient indépendamment associées à la maladie: l'âge, le sexe, un bas état socio-économique, une alimentation peu diversifiée, la déficience en iode et une petite taille du réservoir à eau (présentant un contenu en matiè-res organiques plus élevé). La déficience en sélénium était sévère chez tous les enfants de l'étude. Le degré de contamination fongique des grains d'orge expliquait le plus haut pourcentage de cas (65%) dans le sous-modèle mycologique. L'iode urinaire n'était pas associé à la maladie lorsque Alternaria sp. était isolé. Les résultats sont compatibles avec des dommages oxydatifs aux cellules osseuses en présence d'une défense antioxidante défi-ciente. Un autre mécanisme co-existant possible est le remodelage osseux de l'os stimulé par les hormones thyroidiennes qui peut être bloqué par certaines mycotoxines.

Environmental selenium in the Kaschin–Beck disease area, Tibetan Plateau, China

“…A variety of hypotheses (Fang 1988;Zamana 1995;Chasseur et al 1997;La et al 2001;Chasseur et al 2001;Suetens et al 2001) have been proposed since 1849 when the disease was first discovered in Russia. Selenium deficiency in the environment, organic matter in drinking water, and fungal contamination in stored grains or food are three dominating opinions on the etiology of KBD (Tan et al 1988).…”

The role of selenium in thyroid gland pathophysiology

“…the so-called selenoproteins [28]. The adverse effects caused by selenium deficit and most frequently described in literature include dilated cardiomyopathy (Keshan disease) and endemic osteoarthropathy (Kashin-Beck disease) [28][29][30].…”

The phenomenon of micronutrient deficiency among children in China: a systematic review of the literature

“…The mean serum Se level increased steadily to a non-endemic level in 2000 and attained the highest level in 2005. Two studies conducted in Lhasa Prefecture, an Se-and iodine-deficient area in Tibet, reported that 49 % of 280 subjects had Kashin-Beck disease (67) and all had severe Se deficiency (27) . There was also high Se deficiency rate (83 %) in 120 children aged 6-14 years in Shaanxi Province (93) .…”

“…Keshan disease, a congestive cardiomyopathy, is recognised to be associated with Se deficiency (23) and is endemic in China (24) . Se deficiency is also implicated in Kashin-Beck disease (osteochondropathy) (25) although iodine deficiency is considered common in this disease (26,27) . Ca is required to maintain the rigidity and strength of bones to prevent osteoporosis (28) .…”