In this study, we retrospectively studied demographic and clinical features of T1D and differences between young-onset and adult-onset patients, as well as the trends of prevalence of overweight and obesity. We found that the study patients were characterized by poor blood glucose control, high incidence of dyslipidemia and low detection rate of diabetes-related antibodies. Compared with young-onset T1D, adult-onset patients comprised higher prevalence of diabetes condition in the male gender, higher proportion of obesity and overweight, higher frequency of GADA, better glycemic control and lower frequency of high total cholesterol. To our surprise, no obvious increasing or decreasing trends of overweight and obesity in this population during 2012 and 2018 was observed.
Comparison of Demographic and Clinical Features between this Population and Others
In this analysis, we found that glycemic control was poor among patients with T1D, in whom the median level of HbA1c was 10.3 %. It was similar to the published data from another cross-sectional study in China, which showed that mean HbA1c value was > 75 mmol/mol (9.0%). Compared with the reports from India (8.8%), Sweden (8.2%), the United States (8.2%) and Maccabi (8.1%), the median level of HbA1c found in this study was higher[24, 25]. The differences of level of HbA1c values between different studies may be due to ethnicity, clinical characteristics, parental education, and income level.
There are many studies that reported the prevalence of overweight and obesity of T1D, which varies from 21–53.8% in different countries[24, 26–28]. The current study of children, adolescents and adults showed that the prevalence of being overweight or obesity was 16.9%. In contrast to other countries, the prevalence of overweight or obesity among patients with T1D in China was low.
Dyslipidemia is a common concomitant disease of T1D. The overall prevalence of dyslipidemia among patients with T1D in this study was 37.8%, which was higher than that found in Germany at 28.6%. Similarly, an observation has been documented for patients in Korean with prevalence of 37.9%. In contrast, the prevalence in the present study was much lower than that found in Bangladesh, which reported the overall prevalence of dyslipidemia were 65% in children and adolescents; the high TG, high TC, high LDL and low HDL were found in 50%, 66%, 75%, and 48%, respectively. Also, a higher prevalence was found in Brazilian which reported that the prevalence of dyslipidemia in young patients was72.5%. The wide range of prevalence in various studies may be due to multiple genetic factors in different ethnic groups.
The overall prevalence of retinopathy in our data of 25.2% is comparable with the prevalence of 21% reported from a population-based nationwide Swedish cohort with a median age of 21 yd. Unlike our study, some studies showed lower prevalence of 16% in Norway, 14% in USA and 11% in Germany. However, unlike the previous studies, our study population included a higher proportion of adult-onset patients and a older age at onset, which may account for the differences.
Since this study is a retrospective analysis, data was limited about IA-2A and Znt8. Therefore, it is a pity that we only analyzed the proportion of GADA, ICA, IAA. We observed that the prevalence of GADA, ICA, IAA in the present study were 28.1%, 22.8% and 2.6%, respectively, which were extremely lower than results reported in previous studies[37–41]. As we know, however, the reported prevalence of these autoantibodies in T1DM may vary greatly depending on disease duration, age of onset, antibody assay method and so on. The exact reason for the low prevalence of islet-related antibodies in this study is unclear. One possibility is that other autoantibodies yet to be included maybe contributory. Another reason is the low genetic susceptibilities in this population. Diabetes-related autoantibodies appeared in people with an increased genetic risk of T1D. A study showed that the frequency of GADA is only 30–40% in Asian T1DM patients. It attributed this difference to the fact that autoimmune-mediated β -cell destruction is less common in Asian patients. Besides, the age of subjects in this study maybe associated with the low prevalence of antibodies. As the age of patients were relatively old, they might have had detectable antibodies in the preclinical stage but have become negative before diagnosis. A study demonstrated that with the increase of the age of onset, the newly diagnosed patients without any islet autoantibodies also increased. Besides, compared with patients over 15 years old at onset, IAA was more common in children under 5 years old who developed T1D.
Comparison of clinical features in young-onset and adult-onset patients
It was generally accepted that TID in children were considered to have acute onset with classical symptoms of diabetes, while in adults, the onset of T1D can be more variable and have a better residual beta-cell function. In the analysis of 453 newly diagnosed patients, we observed that elder-onset patients accounted for 48.34 %. It should be noted that elder-onset patients comprised better islet function reflected by FCP and 2-h CP. This result was in line with the results of the Diabetes Control and Complications Trial study and other subsequent studies[45–47]. Besides, the current study found that patients with the adult-onset group had lower median HbA1c levels at disease onset, which indicated that residual β-cell function was better, clinical manifestation was less severe, or hyperglycemia lasted shorter before diagnosis. Different from the traditional view that autoimmune disease are mostly women, T1D is even characterized by a clear male predominance in diabetes for new cases in Caucasians. Similar to previous findings, we found the male excess in present population. In addition, adult-onset group had higher proportion of male patients than young-onset group, agreeing with other studies in China[23, 49] and Finland. The accelerator hypothesis postulated that the heavier child should develop diabetes at a younger age. We discovered a significant difference in prevalence of overweight and obesity between two subgroups, however, adult-onset patients had higher prevalence of overweight or obesity than young-onset patients. Previous studies had reported similar results. For example, Betts et al. showed no association between BMI SDS at diagnosis and age at onset, but an inverse relationship using BMI SDS at 6 months. As previously reported, studies had shown that the adult patients were most frequently tested positive for GADA, which indicated that very young patients tend to mount a weak antibody response to GADA and that the intensity of the GADA response increases with age.
Temporal trends in the prevalence of overweight and obesity
Weight change in TID is complex. Factors that may affect weight gain in patients with T1DM include the level of glycemic control, intensive insulin treatment, pattern of treatment, sexuality, the presence of eating disorders and appearance of complications (such as thyroid disease or gastric disease). Previous studies had shown that T1D had become progressively heavier at disease onset over the past 20 years[54–56]. However, there were no obvious increasing or decreasing trends of overweight and obesity in this population. Weight is associated with Insulin dose. Insulin itself promotes weight gain in that it stimulates lipogenesis, inhibits protein catabolism, and slows basal metabolism. Because of retrospective analysis, we could not get information about insulin dose. It is impossible to explore the relationship between insulin dose and prevalence of overweight or obesity. So, the conclusion needs to be further confirmed by large-scale research.
The limitation of this study is the fact that this study is a retrospective and hospital-based study from one center in Henan province, so the representativeness of the research results is not as good as that of multi-centers. In addition, we cannot fully obtain the clinical data needed for the study.