Role of seasonal factors in pre- and postnatal ontogenesis in etiology of type 1 diabetes mellitus

Type 1 diabetes mellitus is a chronic disease characterized by autoimmune degradation of insulinproducing β-cells. Seasonality of birth of children with type 1 diabetes has been shown in a number of epidemiological studies. It could testify that autoimmune process began during fetal and postnatal development. No such studies were carried out in the former Soviet Union countries. The aim of the present study is to compare the seasonal birth month pattern in patients with type 1 diabetes (10780 men and 9337 women) born in 1960-2003 to that in the total population of Ukraine (14 995768 men and 14 109792 women) born during the same period. Significant differences were found between these two populations: χ 2 = 103.97, p < 0.0001 and 135.17, p < 0.0001 in men and women, respectively. The results of cosinor analysis showed similar sinusoidal birth patterns of patients with type 1 diabetes in all subgroups, irrespective of the age of clinical disease manifestation: 0-9, 10-19, or 20-29 years. In all cases, the highest and lowest predispositions to type 1 diabetes were inherent in the people born in spring and autumn, respectively. In all groups, the highest incidence rate was in persons born in spring and early summer and the lowest ones, in those born in autumn and early winter. We propose that seasonality of birth of patients with type 1 diabetes in the two above populations could be due to long-term programming of glucose-insulin metabolism caused by the effect of certain seasonal factors during early ontogenesis. © Pleiades Publishing, Inc., 2006.