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Lithium content in the population of the Aktobe region of the Republic of Kazakhstan and the relationship with mental illness: a cross-sectional study

The article presents data on the study of the content of lithium in the hair of the adult population of the Aktobe region of the Republic of Kazakhstan and the relationship with mental illness. The aim of the study is to assess the content of lithium in the biosubstrates of the adult population and its relationship with the morbidity of the population of the Aktobe region.Materials and methods: A one-stage cross-sectional study was carried out on the territory of the Aktobe region of the Republic of Kazakhstan. The study included 340 residents aged 18-60 years permanently residing in the study area using the method of simple random sampling. The lithium content in hair was determined by inductively coupled plasma mass spectrometry on a NexION 300D spectrometer (PerkinElmer Inc., USA) equipped with an ESI SC-2 DX4 sampler (Elemental Scientific Inc., USA). The morbidity rates were studied according to the ICD-10 classes per 100 thousand population. To assess the relationship between the Li content in the hair and the morbidity rates, the Spearman rank correlation coefficient was calculated.Results: According to the results of the study, significant deviations from the reference values were observed for the lithium content in the Aktobe region. There is an excess of lithium for 80.59% (CI: 76.38; 84.79) of the subjects, the norm is 19.41% (CI: 15.21; 23.62). Excess lithium is more common in men than in women (χ2  =11.07 df=1; p=0.001). Considering the districts of the Aktobe region, the highest content of Li (Me (q25-q75)) was found in the Aitekebi district (0.084 (0.022 -0.134)) mcg/g, in the Kobda district 0.069 (0.060- 0.076) mcg/g, in the Mugalzhar district 0.046 (0.019-0.066) mcg/g, in the Oiyl district 0.044 (0.021-0.0762) mcg/g, in the Alga district 0.040 (0.024-0.090) mcg/g. Spearman’s correlation rank analysis showed a weak positive association of Li content with age (r=0.20, p =0.0001), no association with body mass index was found (r=0.10, p =0.06). The correlation analysis established a direct inverse average relationship between the content of Li and morbidity in the class of diseases “Mental disorders and behavioral disorders” (r=-0.62; p= 0.044).Conclusions: The high prevalence of excess lithium content in the hair of the population and its relationship with mental illness requires further research. The study of the bioelement status of the population can serve as an indicator of environmental pollution, and also aims at monitoring the ecological situation in the region.