There was no apparent peak age for newly diagnosed type 1 diabetes in Henan Province. In Iran, the peak age of onset is between 5 and 9.9 years [9]. while in Beijing, Japan, and Uzbekistan, it was in adolescence [11, 12, 13]. Contrary to these findings, infant diabetes accounted for 34.5% of the children with diabetes in our study. The incidence of infant diabetes is high in our center because ours is the largest third-level and first-class specialized children's hospital in Henan Province, with advanced professional technology. Thus, parents of young children, especially infants and toddlers, tend to choose our hospital, while those of older children may choose other general hospitals.
The incidence of T1DM peaked in winter, which may be related to the high incidence of virus infections in this season. The seasonal pattern of T1DM onset is well known and has been confirmed repeatedly. In a study from Sweden, the incidence was higher from January to March and lowest from May to July [14]. However, studies from Iraq have shown higher rates in summer [15], which may be linked to different environmental factors. The seasonal distribution of T1DM among children aged 4–9 years in this study was consistent with the results found in Jiangxi Province in China.
The main symptoms before hospital visit were polyuria (72.33%) and polydipsia (79.21%), followed by weight loss (32.94%) and polyphgia (20.2%). A study from Taiwan showed that the most common symptoms were polyuria (96%), polydipsia (92%), dry lips (81%), weight loss (79%)[16]. In this study, it was found that polydipsia and polyuria were more common in infants and school-age children with T1DM, while weight loss was more common in adolescent children. This may be related to the strong self-consciousness of adolescent children and the difficulty in timely detection of symptoms.
One major finding is that 62.96% of the children presented with DKA in this study, and that severe DKA accounted for more than half of the DKA cases. The 0–3-year-olds group had the highest incidence of DKA (70.76%), and no statistical differences were observed between the other two groups. The incidence of DKA varies in different countries and regions [17], with the lowest incidence reported in Denmark (14.7%) and the highest in Saudi Arabia (79.8%). An Iranian study showed a 24% incidence of DKA, of which 54.5% of the cases were severe [9]. Results of multi-center epidemiological investigations are lacking in China. The incidence of DKA in Beijing and Tianjin was 41.1% and 45.6% respectively, among newly diagnosed type 1 diabetes children [10], and there was no statistical difference between different age groups. Studies from Jiangxi Province of China and France showed that the incidence of severe DKA was highest in children aged 0–4 years, which is similar to our findings. However, studies from Finland and New Zealand showed that the incidence of DKA was higher in adolescence [5, 18], which may be related to the lack of detection of symptoms due to the stronger self-consciousness of adolescent children.
About one-third of the children with DKA were complicated with other systemic complications, mainly those of the respiratory and digestive systems. In addition, children could not accurately express the typical symptoms of diabetes, such as polydipsia and polyuria, and caregivers and doctors had insufficient knowledge of the disease; therefore, the diagnosis of DKA was easily delayed, especially in younger children.
In this study, the highest incidence of DKA was found in the 0–3-year-olds group. This group also had the highest blood glucose levels and the lowest C-peptide levels. This reflected that the islet beta-cell function damage and metabolic disorders were more serious at onset in the young age group. Interestingly, the 0–3-year-olds group had the lowest HbA1c levels. This also prompted the more rapid and severe damage of insulin beta cells caused by immune injury, leading to a more serious metabolic disorder. This is consistent with the results of a study conducted in Taiwan [16].
Hospital length of stay and hospitalization costs were highest in the youngest age group. This was possibly related to the high morbidity of DKA and the complications with other systemic diseases in children in the young age group.
Many studies have shown that young age, race, residing in a rural area, and lack of health insurance are the main risk factors for DKA [19, 20]. However, domestic studies have found that rural residence, blood sodium, blood glucose, blood triglyceride and infection are risk factors for DKA [21]. While our findings are different with the domestic studies. In this study, age, HbA1c, C-peptide, 25OHD, and the presence of other systemic comorbidities were all factors associated with DKA. However, we found that age was not an independent risk factor for DKA after multivariate logistic regression analysis. This suggested that age was a confounding factor for DKA.
According to our findings, vitamin D deficiency is widely prevalent in children with T1DM in Henan Province. The serum 25OHD levels among the children in the 0–3-year-olds group were significantly higher than those of the children in the other two groups. Further, there was no statistical difference between the other two groups. A large number of studies have shown that 25OHD has a protective effect on islet β cell function and islet autoimmune and inflammatory responses [22]. Vitamin D deficiency has been linked to an increased incidence of T1DM worldwide, and new research suggests that vitamin D is associated with the incidence of DKA. In a study of 185 children with T1DM in the United States, 33% of the patients had DKA. Out of these cases, the incidence of DKA was 44% in the low vitamin D group and 18% in the vitamin D adequate group: the incidence of DKA in the vitamin D deficient group was significantly higher than that in the vitamin D adequate group [23]. However, an Australian study of the relationship between 25OHD and acidosis showed that acidosis may lead to impaired 1-α-hydroxylase activity to affect the metabolism of vitamin D, or low levels of vitamin D may be T1DM children merger risk factors of DKA, remains to be further discussed [24]. Logistic regression analysis in this study showed that 25-hydroxyvitamin D3 was an independent factor for DKA, which is consistent with the findings of other studies. The incidence of DKA was lowest in children with T1DM with high vitamin D levels; therefore, we recommend that children with T1DM receive vitamin D supplementation.