Regional and ethnic differences in semen quality and reproductive hormones in Russia: a Siberian population-based cohort study of young men.

BACKGROUND This is the first large-scale Russian study describing semen quality and reproductive hormone levels among young men. OBJECTIVES The aim of the study was to compare semen quality and reproductive hormone levels in young men of four cities and three ethnic groups living in the Siberian region of Russia and to find out ethnic or environmental reasons for regional differences. MATERIALS AND METHODS The study population consisted of 1,291 young men from Novosibirsk, Kemerovo, Ulan-Ude and Yakutsk, including 1,013 men of three most numerous ethnic groups: Slavs, Buryats and Yakuts. Each participant provided one sperm and blood sample, information about lifestyle and ethnicity. Anthropometric parameters, semen quality and reproductive hormone levels were evaluated. RESULTS Significant regional and ethnic differences were detected for semen and reproductive hormone parameters. Median sperm concentrations in Novosibirsk, Kemerovo, Ulan-Ude and Yakutsk were 54.6, 39.9, 34.7, 33.1 ×106 /ml; total sperm counts - 202.5, 138.7, 97.9, 93.4 ×106 ; percentages of morphologically normal sperm - 7.8, 6.5, 6.3, 5.0%, respectively. Median sperm concentrations in Slavs, Buryats and Yakuts were 43.7, 37.0, 30.6 ×106 /ml; total sperm counts - 150.0, 102.3 and 74.8 ×106 ; percentages of morphologically normal sperm - 6.8, 6.8, 4.8%, respectively. DISCUSSION The young men in Novosibirsk and Kemerovo, populated by Slavs, had a higher semen quality compared to Ulan-Ude and Yakutsk, populated by Buryats and Yakuts, apparently due to the higher testicular function in Slavic compared to Asian ethnicity. Impaired spermatogenesis in young men in Kemerovo compared to Novosibirsk, located in the same climatic zone and having a socio-cultural and ethnic identity may be due to the influence of a polluted environment. CONCLUSION The findings suggest that ethnic composition and environment may be responsible for regional differences in semen and reproductive hormone parameters.