Epidemiological studies of childhood insulin dependent diabetes

Association of long-term environmental exposures in pregnancy and early life with islet autoimmunity development in children in Bavaria, Germany

OBJECTIVE

Incidence of early-onset type 1 diabetes (T1D) has been increasing worldwide. Only few studies examined the relationship between geographical environmental variation and T1D incidence or its presymptomatic stage of islet autoimmunity. Our study aimed to investigate the effect of long-term environmental exposures during pregnancy and early life on childhood islet autoimmunity.

RESEARCH DESIGN AND METHODS

We used data from the Fr1da cohort study which screened children aged 1.75-5.99 years for multiple islet autoantibodies in Bavaria, Germany between 2015 and 2019. We included 85,251 children with valid residential information. Daily averages for particulate matter with a diameter <2.5 μm, nitrogen dioxide, ozone, air temperature, and greenness were averaged for each zip-code or directly assigned to the addresses. The exposure windows included pregnancy, the first year and the first two years of life. Generalized additive models adjusting for individual and socioeconomic variables were used to investigate associations between environmental exposures and islet autoimmunity development.

RESULTS

Islet autoimmunity was diagnosed in 272 children. Colder air temperature during pregnancy was associated with developing islet autoimmunity at the address (per 2.2 °C decrease, Odds ratio (OR): 1.49; 95% Confidence interval (CI): 1.21-1.83) and zip-code level (per 2.4 °C decrease, OR: 1.31; 95% CI: 1.08-1.59). Using the addresses, significant associations were also observed during the first years of life.

CONCLUSION

In this study, children's residential exposure to lower levels of air temperature during pregnancy and early life increased the risk of islet autoimmunity before the age of six.

Incidence and seasonal variation of Type 1 diabetes in children in Farwania area, Kuwait (1995-1999)

The aim of our study was to confirm the continuing rise in the incidence of Type 1 diabetes among Kuwaiti children aged 0-14, and to assess the effect of seasonality on incidence. Data from all newly diagnosed diabetic children between the period of 1995 and 1999 were analyzed. A total of 129 cases of Type 1 diabetes were diagnosed during the study period, of whom 68 were Kuwaiti nationals and were included in the study. The incidence was 20.18 per 100,000 (95% CI 16.3-28.2). Incidence rates for the age-groups 0-4, 5-9 and 10-14 were 8.12, 21.07 and 34.06, respectively. There was a significant female predominance (F:M ratio was 1.4:1, P<0.05). More cases were diagnosed in the cool months (November-February) compared with the warm months (June-September, P<0.05). There was increase in incidence from 1995 to 1999, but compared with data from the 1980s on the same age group, incidence has increased. A positive family history of Type 1 diabetes in a close relative was recorded for 30% of the patients. Although, only data from one hospital were included, Kuwait is very small geographically and not likely to have differences between different areas. Stress factors, economic growth, changes in the nutritional habits and the adoption of the western lifestyle may explain some of this increase.

Incidence of insulin-dependent diabetes mellitus in Jordanian children aged 0-14 y during 1992-1996

An attempt was made by the Jordanian National Center for Diabetes, Endocrine and Genetic Diseases (NCDEGD) to identify all cases of type 1 diabetes among Jordanian children aged 0-14 y. Data were obtained retrospectively for the years 1992-1994 and prospectively for the years 1995 and 1996, including full name, national identifying number, date of birth, date of diagnosis and family history. The incidence was calculated as the number of cases per 100,000 population, according to the national census of 1994. The incidence rate for these years (1992 through 1996) was 2.8, 2.9, 3.2, 3.6 and 3.6 per 100,000 population, respectively. The male:female ratio was (1:1.03). Seasonal variation at clinical onset was noticed, with maximum incidence in the winter months and minimum incidence in the summer months. In conclusion, the incidence of type 1 diabetes mellitus in Jordanian children aged 0-14 y is among the lowest in the region, but is rising.

The aetiology of type 1 diabetes: an epidemiological perspective

Type 1 diabetes is increasing rapidly in many parts of the Western world, most evidently in Scandinavia. A low concordance rate of insulin-dependent diabetes mellitus among monozygotic twins clearly indicates that genetic risk factors may be necessary, but are not sufficient for the disease to occur. The strongest genetic risk markers are located in the HLA region of chromosome 6, but these DNA specificities differ in different populations. Risk genes are indicated in other chromosomes of the human genome, suggesting a complex interaction between genes and environment as the cause of the disease. The pathogenesis of the disease is proposed to be autoimmune in nature and environmental risk factors may either initiate autoimmunity or accelerate an already ongoing beta-cell destruction. Risk factors disclosed by epidemiological studies that may accelerate the pathogenetic process are: a cold environment, a high growth rate, infections and stressful life events. Risk factors that may initiate the autoimmune process include early exposure to cow's milk proteins, nitrosamines or early foetal events such as blood group incompatibility or foetal viral infections. In conclusion, population-based epidemiological studies have helped to confirm proposed aetiological models that have arisen from experimental research. These epidemiological studies have also introduced important new findings that may reveal the complex aetiology of the disease and advance understanding closer to the ultimate goal of primary prevention.

Viruses and other perinatal exposures as initiating events for beta-cell destruction

There is strong evidence that the aetiology of insulin-dependent diabetes mellitus (IDDM) is due to a complex interaction between genes and the environment and that the pathogenesis is autoimmune. In early perinatal life the immune system is induceable and exposures in this period may initiate autoimmunity. Recent findings of time and space clustering of birth dates for later diabetic cases together with the early observation of a very high prevalence of diabetes in cases with rubella embryopathy suggest that foetal virus exposure may be important. Recent findings from Sweden and Finland suggest that enterovirus exposure during foetal life may initiate autoimmunity which may lead to diabetes. Other immune events, such as maternal-foetal blood group incompatibility and pre-eclampsia in the mother have also been associated with IDDM risk. Other more unspecific events in the perinatal period, such as a short gestational age, caesarean section and neonatal respiratory disease, are also indicated to increase the risk. In addition, food components such as nitrosamine components, cow's milk protein and gliadin have been proposed to initiate the slowly progressing autoimmune beta-cell destruction. Most of these epidemiological findings are supported by experimental studies in the nonobese diabetic mice but their exact mechanisms of action are still unclear. It is concluded that new evidence is accumulating indicating that perinatal exposures may be important for the initiation of beta-cell destruction. As such risk factors may be targets for primary prevention strategies further studies are urgently warranted.

Non-genetic risk determinants for type 1 (insulin-dependent) diabetes mellitus in childhood. Hungarian Childhood Diabetes Epidemiology Study Group

Using the prospective Hungarian childhood diabetes register, a nationwide case-control study was carried out to investigate the possible role of various non-genetic factors as risk determinants for type 1 diabetes in childhood. A questionnaire (covering family characteristics, social status, fetal and perinatal events, breast-feeding habits, infectious diseases and stressful life events) was sent by mail to all incident diabetic children in 1990 (n = 163) and to two referent children (for each diabetic child), matched for age, sex and county. Diabetic children had a tendency to have mothers > 35 years of age (odds ratio (OR) = 3.52; 95% confidence intervals (CI) 0.74-16.79), a lower proportion of their mothers had higher education (OR = 1.69; 95% CI 0.95-3.0) and these children tended to move home more frequently (OR = 1.99; 95% CI 0.97-4.1). Although the duration of exclusive breast feeding was similar in both groups, the proportion of diabetic children who received no breast milk tended to be higher (OR = 1.76; 95% CI 0.91-3.4). A higher proportion of diabetic children reported non-specific infections (OR = 2.94; 95% CI 1.19-7.21) and the number of stressful life events was higher in diabetic children aged 10-14 years (OR = 3.9; 95% CI 1.14-13.27). As the risk determinants for childhood insulin-dependent diabetes mellitus identified in our low-risk population appear to be similar to those detected in the genetically different, high-risk Swedish population, our study strongly supports an etiological role for these non-genetic risk factors in IDDM.

Etiological aspects of insulin-dependent diabetes mellitus: an epidemiological perspective

The mechanism of beta-cell destruction leading to insulin dependent diabetes is probably a cell mediated auto-immune process occurring in genetically susceptible individuals. Since 50-70% of monozygotic twins will not get the disease non-genetic risk factors must play an important role in the etiology of the disease. During the past decade population based epidemiological studies have identified several risk determinants for insulin dependent diabetes. Based on these studies a multifactorial hypothesis of causation is proposed. Some risk determinants (maternal child blood group incompatibility, fetal viral infections, early exposure to cow's milk proteins, a high exposure level of nitrosamines) may independently initiate the autoimmune process by causing the initial damage of the beta-cell, leading to antigen release. Other risk determinants may promote an already ongoing autoimmune destructive process through induction of lymphokine release or by causing an increased work load on the beta-cell. Risk factors that may increase the peripheral need for insulin (infectious diseases, cold environment, a high growth rate and stressful life events) may act as promoters of the beta-cell destruction but also disclose the beta-cell impairment and make the disease clinically overt. Possibilities of different risk profiles in different age groups and of synergism between different risk factors are also discussed.

Maternal-child blood group incompatibility and other perinatal events increase the risk for early-onset type 1 (insulin-dependent) diabetes mellitus

The nationwide Swedish Childhood Diabetes Registry, which ascertains 99% of recent-onset Type 1 (insulin-dependent) diabetic children (0-14 years) in Sweden, was linked with the Swedish Medical Birth Registry. A matched case-control study was carried out analysing about 20 perinatal variables concerning mother and child. A total of 2757 infants who became diabetic during the period 1978-1988 were analysed. For each case infant three control children were randomly selected from among all infants born in the same year and at the same delivery unit as the case infant. The following statistically significant risk factors were identified for Type 1 diabetes with an onset before 15 years of age: maternal diabetes (OR = 3.90), maternal age above 35 (OR = 1.36), maternal non-smoking (OR = 1.54), pre-eclamptic toxaemia (OR = 1.19), caesarian section (OR = 1.32), and maternal-child blood group incompatibility (OR = 1.61). When the analysis was restricted to Type 1 diabetes with an onset before the age of 5 years, most odds ratios were increased - for blood group incompatibility OR = 3.86 (95% confidence interval 1.54-9.65). Icterus without blood group incompatibility was not a significant risk factor. When each risk factor was analysed after standardization for all other risk factors, the odds ratios remained significantly increased. Scrutiny of medical records for cases and control children with a diagnosis of blood group incompatibility verified the diagnosis in close to 90% of children. The more severe cases needing phototherapy and/or blood transfusion were found to have a greater risk than milder cases.(ABSTRACT TRUNCATED AT 250 WORDS)