Epidemiology of childhood IDDM in Northern Ireland 1989-1994: low incidence in areas with highest population density and most household crowding. Northern Ireland Diabetes Study Group

Predicting the development of T1D and identifying its Key Performance Indicators in children; a case-control study in Saudi Arabia

The increasing incidence of type 1 diabetes (T1D) in children is a growing global concern. It is known that genetic and environmental factors contribute to childhood T1D. An optimal model to predict the development of T1D in children using Key Performance Indicators (KPIs) would aid medical practitioners in developing intervention plans. This paper for the first time has built a model to predict the risk of developing T1D and identify its significant KPIs in children aged (0-14) in Saudi Arabia. Machine learning methods, namely Logistic Regression, Random Forest, Support Vector Machine, Naive Bayes, and Artificial Neural Network have been utilised and compared for their relative performance. Analyses were performed in a population-based case-control study from three Saudi Arabian regions. The dataset (n = 1,142) contained demographic and socioeconomic status, genetic and disease history, nutrition history, obstetric history, and maternal characteristics. The comparison between case and control groups showed that most children (cases = 68% and controls = 88%) are from urban areas, 69% (cases) and 66% (control) were delivered after a full-term pregnancy and 31% of cases group were delivered by caesarean, which was higher than the controls (χ2 = 4.12, P-value = 0.042). Models were built using all available environmental and family history factors. The efficacy of models was evaluated using Area Under the Curve, Sensitivity, F Score and Precision. Full logistic regression outperformed other models with Accuracy = 0.77, Sensitivity, F Score and Precision of 0.70, and AUC = 0.83. The most significant KPIs were early exposure to cow's milk (OR = 2.92, P = 0.000), birth weight >4 Kg (OR = 3.11, P = 0.007), residency(rural) (OR = 3.74, P = 0.000), family history (first and second degree), and maternal age >25 years. The results presented here can assist healthcare providers in collecting and monitoring influential KPIs and developing intervention strategies to reduce the childhood T1D incidence rate in Saudi Arabia.

The hygiene hypothesis for allergy - conception and evolution

In 1989, a short paper entitled "Hay fever, hygiene and household size" observed that British children from larger families were less likely to develop hay fever and suggested that this could be because early exposure to infection prevents allergy. This sibship size association for hay fever, since replicated many times in Britain and other affluent countries and confirmed by objective measures of atopy, prompted what has come to be known as the "hygiene hypothesis for allergy", although that term was not specifically used in the 1989 paper. The present paper reviews the historical roots of the "hygiene hypothesis" and charts its development over more than 30 years. Initial scepticism among immunologists turned to enthusiasm in the mid-1990s as the Th1/Th2 paradigm for allergic sensitisation emerged from animal experiments and the concept of "immunological old friends" became popular from the early 2000s. From the late 1990s, observations of reduced allergy risk among children of anthroposophic families and those brought up on farms suggested that the sibship size effects formed part of a broader range of "hygiene-related" determinants of allergy. Children from large families with farming exposure have approximately sixfold reduction in prevalence of hay fever, indicating the potential strength and epidemiological importance of these environmental determinants. During the 21st century, a wide range of specific microbial, environmental and lifestyle factors have been investigated as possible underlying mechanisms, but sadly none have emerged as robust explanations for the family size and farming effects. Thus, while the "hygiene hypothesis" led to a fundamental reappraisal of our relationship with our microbial environment and to the concept that early exposure, rather than avoidance, is beneficial for developing a healthy immune system, the underlying mechanism for variations in allergy prevalence with family size remains, in Churchillian terms, "a riddle wrapped in a mystery inside an enigma".

Incidence of type 1 diabetes among children and adolescents during peace and war times in Yemen

AIM

To calculate a 30-year incidence rates of type 1 diabetes (T1D) in Sana'a city, Yemen during peace and wartimes.

METHODS

A total of 461 patients aged between 8 months and 18 years with newly diagnosed diabetes were registered between 1989 and 2018. We used a standardized protocol for counting cases over time. The annual incidence rates (cases/100,000/year) were calculated from the number of new reported cases for each year divided by the estimated number of person-years "at risk" resident in Sana'a city, Yemen according to age and sex of the participants of that year.

RESULTS

The mean annual incidence rate of T1D in children aged 0-14 years was 1.83/100,000/year. With the use of 3-year time-periods, the mean annual incidence rate was (5/100,000/year) in the first time-period, fluctuated between 1.2 and 2.3 during subsequent seven time-periods, and declined to (0.5/100,000/year) during the conflict years. The age-specific mean annual incidence rates for age-groups 0-4, 5-9, 10-14, and 15-18 years were 0.83, 1.82, 3.14, and 2.31/100,000/year, respectively.

CONCLUSION

The mean annual incidence rate of T1D in children and adolescents over the observation period in Sana'a city was low. In children aged 0-14 years in particular, the incidence declined to a very low rate during wartime. Interpretation is partly limited by lack of recent census data, and the possibility of death from nondiagnosis at onset.

The impact of race and socioeconomic factors on paediatric diabetes

There are over 29,000 children and young people (CYP) with Type 1 diabetes mellitus (T1DM) in England and Wales and another 726 with Type 2 diabetes mellitus (T2DM). There is little effect of deprivation on the prevalence of T1DM whereas the association of deprivation on the percentage of CYP with T2DM is striking with 45% of cases drawn from the most deprived backgrounds. A number that has not changed over the last 4 years. Data from the UK and USA as well as other countries demonstrate the impact of deprivation on outcomes in diabetes mellitus with clear effects on measures of long-term control and complications. In the UK black CYP had higher glycosylated haemoglobin (HbA1c) values compared to other groups. Within the black group, CYP from a Caribbean background had a higher mean HbA1c (77.0 mmol/mol (9.2%)) than those from Africa (70.4 mmol/mol (8.6%)). Treatment regimen (multiple daily injections or insulin pump therapy) explained the largest proportion of the variability in HbA1c followed by deprivation. Those in the least deprived areas had an average HbA1c 5.88 mmol/mol (0.5%) lower than those living in the most deprived areas. The picture is complex as UK data also show that deprivation and ethnicity is associated with less use of technology that is likely to improve diabetes control. Increased usage of pump therapy and continuous glucose monitoring was associated with a younger age of patient (less than 10 years of age), living in the least deprived areas and white ethnicity. This gap between pump usage amongst CYP with T1DM living in the most and least deprived areas has widened with time. In 2014/15 the gap was 7.9% and by 2018/19 had increased to 13.5%. To attain an equitable service for CYP with diabetes mellitus we need to consider interventions at the patient, health care professional, community, and health care system levels.

Type 1 Diabetes incidence among youth in Utah: A geographical analysis

Type 1 Diabetes (T1D) poses an increasing threat to public health, as incidence rates continue to rise globally. However, the etiology of T1D is still poorly understood, especially from the perspective of geography. The objective of this research is to examine the incidence of T1D among youth and to identify high-risk clusters and their association with socio-demographic and geographic variables. The study area was the entire state of Utah and included youth with T1D from birth to 19 years of age from 1998 to 2015 (n = 4161). Spatial clustering was measured both globally and locally using the Moran's I statistic and spatial scan statistic. Ordinary least squares (OLS) regression was used to measure the association of high-risk clusters with certain risk factors at the Census Block Group (CBG) level. The mean age at diagnosis was 9.3 years old. The mean incidence rate was 25.67 per 100,000 person-years (95% CI, 24.57-26.75). The incidence rate increased by 14%, from 23.94 per100,000 person-years in 1998 to 27.98 per 100,000 person-years in 2015, with an annual increase of 0.80%. The results of the spatial scan statistic found 42 high-risk clusters throughout the state. OLS regression analysis found a significant association with median household income, population density, and latitude. This study provides evidence that incidence rates of T1D are increasing annually in the state of Utah and that significant geographic high-risk clusters are associated with socio-demographic and geographic factors.

BCG immunomodulation: From the 'hygiene hypothesis' to COVID-19

The century-old tuberculosis vaccine BCG has been the focus of renewed interest due to its well-documented ability to protect against various non-TB pathogens. Much of these broad spectrum protective effects are attributed to trained immunity, the epigenetic and metabolic reprogramming of innate immune cells. As BCG vaccine is safe, cheap, widely available, amendable to use as a recombinant vector, and immunogenic, it has immense potential for use as an immunotherapeutic agent for various conditions including autoimmune, allergic, neurodegenerative, and neoplastic diseases as well as a preventive measure against infectious agents. Of particular interest is the use of BCG vaccination to counteract the increasing prevalence of autoimmune and allergic conditions in industrialized countries attributable to reduced infectious burden as described by the ‘hygiene hypothesis.’ Furthermore, BCG vaccination has been proposed as a potential therapy to mitigate spread and disease burden of COVID-19 as a bridge to development of a specific vaccine and recombinant BCG expression vectors may prove useful for the introduction of SARS-CoV-2 antigens (rBCG-SARS-CoV-2) to induce long-term immunity. Understanding the immunomodulatory effects of BCG vaccine in these disease contexts is therefore critical. To that end, we review here BCG-induced immunomodulation focusing specifically on BCG-induced trained immunity and how it relates to the ‘hygiene hypothesis’ and COVID-19.

Associations of area deprivation and urban/rural traits with the incidence of type 1 diabetes: analysis at the municipality level in North Rhine-Westphalia, Germany

AIM

To analyse the associations of area deprivation and urban/rural traits with the incidence of type 1 diabetes in the German federal state of North Rhine-Westphalia.

METHODS

Data of incident type 1 diabetes cases in children and adolescents aged <20 years between 2007 and 2014 were extracted from a population-based diabetes register. Population data, indicators of area deprivation and urban/rural traits at the municipality level (396 entities) were obtained from official statistics. Area deprivation was assessed in five groups based on quintiles of an index of multiple deprivation and its seven deprivation domains. Poisson regression accounting for spatial dependence was applied to investigate associations of area deprivation and urban/rural traits with type 1 diabetes incidence.

RESULTS

Between 2007 and 2014, 6143 incident cases were reported (99% completeness); the crude incidence was 22.3 cases per 100 000 person-years. The incidence decreased with increasing employment and environmental deprivation (relative risk of the most vs. the least deprived municipalities: 0.905 [95% CI: 0.813, 1.007] and 0.839 [0.752, 0.937], respectively) but was not associated with the composite deprivation index. The incidence was higher in more peripheral, rural, smaller and less densely populated municipalities, and the strongest association was estimated for the location trait (relative risk of peripheral/very peripheral compared with very central location: 1.231 [1.044, 1.452]).

CONCLUSIONS

The results suggest that the type 1 diabetes risk is higher in more remote, more rural, less densely populated and less deprived areas. Urban/rural traits were stronger predictors of type 1 diabetes risk than area deprivation indicators.

Incidence of type 1 diabetes by socio-demographic characteristics among South Australian children: Whole-of-population study

AIM

To describe and compare the incidence of type 1 diabetes (T1D) in South Australia by individual and area-level socio-economic characteristics among children aged ≤11 years.

METHODS

This is a whole-of-population, data linkage study (n = 231 685) conducted in South Australia, and included children born from 2002 to 2013, hospitalisation followed from 2002 to 2014. The study used de-identified, linked administrative hospitalisation, birth and perinatal data from the South Australian Early Childhood Data Project. Incidence was calculated by identifying T1D cases from T1D-related hospitalisations using International Classification of Disease, 10th Revision, Australian Modification diagnosis codes (E10, E101-E109).

RESULTS

Overall, 333 children aged ≤11 years (173 boys) were identified as having T1D. The T1D incidence rate was 23.0 per 100 000 person-years (95% confidence interval (CI): 20.7-25.7), with no sex difference. T1D incidence was higher among children whose mothers were Caucasian, private patients and whose parents were employed. For example, T1D incidence was 26.0 per 100 000 (95% CI: 22.8-29.5) among children with both parents employed, compared to 20.0 per 100 000 (95% CI: 12.3-30.6) among children with both parents unemployed. There was no clear gradient in the association between area-level socio-economic position and T1D, with highest incidence for the fourth quintile (26.5 per 100 000 (95% CI: 20.9-33.1)). The most advantaged area (19.4 per 100 000 (95% CI: 13.8-26.5)) had lower incidence than the most disadvantaged area (23.5 per 100 000 (95% CI: 18.9-28.9)).

CONCLUSION

T1D incidence rates differed depending on the measures of socio-economic characteristics. Individual-level indicators showed higher incidence among more advantaged children; however, there was no clear area-level socio-economic patterning of T1D.

Innate Viral Sensor MDA5 and Coxsackievirus Interplay in Type 1 Diabetes Development

Type 1 diabetes (T1D) is a polygenic autoimmune disease characterized by immune-mediated destruction of insulin-producing β-cells. The concordance rate for T1D in monozygotic twins is ≈30-50%, indicating that environmental factors also play a role in T1D development. Previous studies have demonstrated that enterovirus infections such as coxsackievirus type B (CVB) are associated with triggering T1D. Prior to autoantibody development in T1D, viral RNA and antibodies against CVB can be detected within the blood, stool, and pancreata. An innate pathogen recognition receptor, melanoma differentiation-associated protein 5 (MDA5), which is encoded by the IFIH1 gene, has been associated with T1D onset. It is unclear how single nucleotide polymorphisms in IFIH1 alter the structure and function of MDA5 that may lead to exacerbated antiviral responses contributing to increased T1D-susceptibility. Binding of viral dsRNA via MDA5 induces synthesis of antiviral proteins such as interferon-alpha and -beta (IFN-α/β). Viral infection and subsequent IFN-α/β synthesis can lead to ER stress within insulin-producing β-cells causing neo-epitope generation, activation of β-cell-specific autoreactive T cells, and β-cell destruction. Therefore, an interplay between genetics, enteroviral infections, and antiviral responses may be critical for T1D development.

Childhood type 1 diabetes: an environment-wide association study across England

AIMS/HYPOTHESIS

Type 1 diabetes is an autoimmune disease affecting ~400,000 people across the UK. It is likely that environmental factors trigger the disease process in genetically susceptible individuals. We assessed the associations between a wide range of environmental factors and childhood type 1 diabetes incidence in England, using an agnostic, ecological environment-wide association study (EnWAS) approach, to generate hypotheses about environmental triggers.

METHODS

We undertook analyses at the local authority district (LAD) level using a national hospital episode statistics-based incident type 1 diabetes dataset comprising 13,948 individuals with diabetes aged 0-9 years over the period April 2000 to March 2011. We compiled LAD level estimates for a range of potential demographic and environmental risk factors including meteorological, land use and environmental pollution variables. The associations between type 1 diabetes incidence and risk factors were assessed via Poisson regression, disease mapping and ecological regression.

RESULTS

Case counts by LAD varied from 1 to 236 (median 33, interquartile range 24-46). Overall type 1 diabetes incidence was 21.2 (95% CI 20.9, 21.6) per 100,000 individuals. The EnWAS and disease mapping indicated that 15 out of 53 demographic and environmental risk factors were significantly associated with diabetes incidence, after adjusting for multiple testing. These included air pollutants (particulate matter, nitrogen dioxide, nitrogen oxides, carbon monoxide; all inversely associated), as well as lead in soil, radon, outdoor light at night, overcrowding, population density and ethnicity. Disease mapping revealed spatial heterogeneity in type 1 diabetes risk. The ecological regression found an association between type 1 diabetes and the living environment domain of the Index of Multiple Deprivation (RR 0.995; 95% credible interval [CrI] 0.991, 0.998) and radon potential class (RR 1.044; 95% CrI 1.015, 1.074).

CONCLUSIONS/INTERPRETATION

Our analysis identifies a range of demographic and environmental factors associated with type 1 diabetes in children in England.

The hygiene hypothesis in autoimmunity: the role of pathogens and commensals

The incidence of autoimmune diseases has been steadily rising. Concomitantly, the incidence of most infectious diseases has declined. This observation gave rise to the hygiene hypothesis, which postulates that a reduction in the frequency of infections contributes directly to the increase in the frequency of autoimmune and allergic diseases. This hypothesis is supported by robust epidemiological data, but the underlying mechanisms are unclear. Pathogens are known to be important, as autoimmune disease is prevented in various experimental models by infection with different bacteria, viruses and parasites. Gut commensal bacteria also play an important role: dysbiosis of the gut flora is observed in patients with autoimmune diseases, although the causal relationship with the occurrence of autoimmune diseases has not been established. Both pathogens and commensals act by stimulating immunoregulatory pathways. Here, I discuss the importance of innate immune receptors, in particular Toll-like receptors, in mediating the protective effect of pathogens and commensals on autoimmunity.

Genetic and environmental factors affect the onset of type 1 diabetes mellitus

BACKGROUND

Type 1 diabetes mellitus (T1DM) is influenced by genetic as well as environmental factors. Its incidence has risen considerably since the 1950s.

OBJECTIVE

This study investigates T1DM time trends from 1989 to 2008 and tries to establish whether breast/bottle feeding, a family history of diabetes, and childhood infectious diseases influence age at onset.

METHODS

The study used the population-based registry of childhood diabetes of Abruzzo (central Italy), which includes incident cases of patients aged less than 15 yr. The pooled 1989-2008 global ascertainment of the registry was 95%. The trend was estimated using age-period-cohort models RESULTS: Overall standardized incidence rates (SIR) increased by 73.38% from 8.94 (1989-1993) to 15.50 (2004-2008). A rising trend was found in all age groups; annual rises were significant for the overall population (3.40%, p < 0.01) and for 5-9 yr olds (5.48%, p < 0.01). SIR increased in males by 106.26%, from 9.26 in 1989-1993 to 19.10 in 2004-2008. Early T1DM onset was related to mixed feeding (6.80 yr ± 3.58 vs 8.20 ± 3.81 yr; p = 0.002), and a family history of T1DM (6.71 ± 3.96 yr vs. 8.09 ± 3.77 yr; p = 0.014), whereas multiple infections delayed age at onset (9.71 ± 2.37 yr vs 7.71 ± 2.82 yr; p = 0.03).

CONCLUSIONS

T1DM incidence exhibits a rising time trend that is particularly evident in males and in middle age group; mixed feeding and a family history of diabetes are associated with early onset, multiple bacterial infections contracted before diabetes are associated with a significant delay.

Trends in the incidence of childhood type 1 diabetes mellitus in Beijing based on hospitalization data from 1995 to 2010

OBJECTIVES

To study the incidence trend of type 1 diabetes mellitus (T1DM) in children in Beijing from 1995 to 2010, to compare it with incidences reported worldwide and to predict the requirement of medical resources in the future.

METHODS

This study involved newly diagnosed T1DM cases younger than 15 years of age in the Beijing Children's Hospital from January 1995 to December 2010. We calculated the incidence of T1DM children in Beijing according to hospitalization data and Beijing's population. We defined it as the underestimated incidence rate (UE-IR).

RESULTS

The UE-IRs of T1DM ranged from around 0.88/100,000 to 2.37/100,000 for children in Beijing younger than 15 years of age from 1995 to 2010. The UE-IR increased faster in boys (1.47 times) and in the age group of 0-4 years (1.89 times) after 2003. The UE-IR was greatest in children aged 5-9 years (1.81/100,000) followed by the age of puberty (10-14 years, 1.76/100,000). The predicted number of new T1DM cases in Beijing will increase 1.97 times over the next 10 years.

CONCLUSIONS

The incidence trend of T1DM was increasing gradually in those younger than 15 years of age in Beijing. The incidence of younger children and boys grew faster. The 5- to 14-year-old children represented a high-risk population of T1DM. The number of predicted new T1DM cases will grow rapidly. This means that we should train more health care providers for pediatric diabetes patients, in order to achieve high-quality medical care and to be able to prevent or postpone chronic complications.

Microbiome manipulation modifies sex-specific risk for autoimmunity

Despite growing evidence for a causal role of environmental factors in autoimmune diseases including the rise in disease frequencies over the past several decades we lack an understanding of how particular environmental exposures modify disease risk. In addition, many autoimmune diseases display sex-biased incidence, with females being disproportionately affected but the mechanisms underlying this sex bias remain elusive. Emerging evidence suggests that both host metabolism and immune function is crucially regulated by the intestinal microbiome. Recently, we showed that in the non-obese diabetic (NOD) mouse model of Type 1 Diabetes (T1D), the gut commensal microbial community strongly impacts the pronounced sex bias in T1D risk by controlling serum testosterone and metabolic phenotypes (1). Here we present new data in the NOD model that explores the correlations between microbial phylogeny, testosterone levels, and metabolic phenotypes, and discuss the future of microbiome-centered analysis and microbe-based therapeutic approaches in autoimmune diseases.

Conventional housing conditions attenuate the development of experimental autoimmune encephalomyelitis

BACKGROUND

The etiology of multiple sclerosis (MS) has remained unclear, but a causative contribution of factors outside the central nervous system (CNS) is conceivable. It was recently suggested that gut bacteria trigger the activation of CNS-reactive T cells and the development of demyelinative disease.

METHODS

C57BL/6 (B6) mice were kept either under specific pathogen free or conventional housing conditions, immunized with the myelin basic protein (MBP)-proteolipid protein (PLP) fusion protein MP4 and the development of EAE was clinically monitored. The germinal center size of the Peyer's patches was determined by immunohistochemistry in addition to the level of total IgG secretion which was assessed by ELISPOT. ELISPOT assays were also used to measure MP4-specific T cell and B cell responses in the Peyer's patches and the spleen. Ear swelling assays were performed to determine the extent of delayed-type hypersensitivity reactions in specific pathogen free and conventionally housed mice.

RESULTS

In B6 mice that were actively immunized with MP4 and kept under conventional housing conditions clinical disease was significantly attenuated compared to specific pathogen free mice. Conventionally housed mice displayed increased levels of IgG secretion in the Peyer's patches, while the germinal center formation in the gut and the MP4-specific TH17 response in the spleen were diminished after immunization. Accordingly, these mice displayed an attenuated delayed type hypersensitivity (DTH) reaction in ear swelling assays.

CONCLUSIONS

The data corroborate the notion that housing conditions play a substantial role in the induction of murine EAE and suggest that the presence of gut bacteria might be associated with a decreased immune response to antigens of lower affinity. This concept could be of importance for MS and calls for caution when considering the therapeutic approach to treat patients with antibiotics.

The hygiene hypothesis: an explanation for the increased frequency of insulin-dependent diabetes

The steadily increasing frequency of insulin-dependent diabetes in several countries is best explained today by the decline of infections. Epidemiologic and animal data support this conclusion, which, however, requires confirmation by intervention trials in man. The mechanisms of the protective effect of infections on diabetes onset are diverse including competition for homeostatic factors and stimulation of regulatory T cells and of Toll-like receptors. These considerations might have interesting therapeutic applications for the prevention of the disease.

How do childhood diagnoses of type 1 diabetes cluster in time?

Background

Previous studies have indicated that type 1 diabetes may have an infectious origin. The presence of temporal clustering—an irregular temporal distribution of cases—would provide additional evidence that occurrence may be linked with an agent that displays epidemicity. We tested for the presence and form of temporal clustering using population-based data from northeast England.

Materials and Methods

The study analysed data on children aged 0–14 years diagnosed with type 1 diabetes during the period 1990–2007 and resident in a defined geographical region of northeast England (Northumberland, Newcastle upon Tyne, and North Tyneside). Tests for temporal clustering by time of diagnosis were applied using a modified version of the Potthoff-Whittinghill method.

Results

The study analysed 468 cases of children diagnosed with type 1 diabetes. There was highly statistically significant evidence of temporal clustering over periods of a few months and over longer time intervals (p<0.001). The clustering within years did not show a consistent seasonal pattern.

Conclusions

The study adds to the growing body of literature that supports the involvement of infectious agents in the aetiology of type 1 diabetes in children. Specifically it suggests that the precipitating agent or agents involved might be an infection that occurs in “mini-epidemics”.

Early life socioeconomic indicators and risk of type 1 diabetes in children and young adults

OBJECTIVE

To examine the potential role of 2 early-life socioeconomic indicators, parental education, and crowding index, on risk of type 1 diabetes (T1DM) in patients up to age 29 years to test heterogeneity by age at onset according to the hygiene hypothesis.

STUDY DESIGN

The study base was 330 950 individuals born from 1967 to 2006 who resided in the city of Turin at any time between 1984 and 2007. Data on their early life socioeconomic position were derived from the Turin Longitudinal Study; 414 incident cases of T1DM up to age 29 years were derived from the Turin T1DM registry.

RESULTS

Socioeconomic indicators had opposing effects on risk of T1DM in different age at onset subgroups. In a Poisson regression model that included both socioeconomic indicators, there was a 3-fold greater risk of T1DM (relative risk 2.91, 95% CI 0.99-8.56) in children age 0-3 years at diagnosis living in crowded houses. In the 4- to 14-year subgroup, a low parental educational level had a protective effect (relative risk 0.50, 95% CI 0.29-0.84), and the effect of crowding nearly disappeared. In the 15- to 29-year subgroup, neither crowding nor parental educational level was clearly associated with the incidence of T1DM.

CONCLUSIONS

We provide evidence of heterogeneity by age at onset of the association between early-life socioeconomic indicators and the risk of T1DM. This finding is consistent with the hypothesis that infectious agents in the perinatal period may increase the risk, whereas in the following years they may become protective factors (hygiene hypothesis).

Incidence of type 1 diabetes mellitus in Turkish children from the southeastern region of the country: a regional report

OBJECTIVE

Variability in the incidence of type 1 diabetes mellitus (T1DM) related to geographical region, ethnic background, gender, and age indicates a need for further epidemiological studies. To date, there are no reported studies on the incidence of T1DM in the pediatric age group from the Southeastern region of Turkey. To define the incidence, demographic and clinical characteristics of T1DM in children 0-14 years of age in Diyarbakir, one of the largest cities in the Southeast region of Turkey.

METHODS

Hospital files of patients with the diagnosis of T1DM were reviewed. Data of all patients diagnosed between 1 June 2010 and 31 May 2011 were evaluated. Population data on the 0-14 age group were obtained from the Turkish Statistical Institute (TSI) reports.

RESULTS

From a total of 41 T1DM patients, 24 (58.5%) were female (male: 41.5%) with a male/female ratio of 1.4. The overall annual incidence of T1DM was 7.2/10(5), being 8.7/10(5) in females and 5.7/10(5) in males. The peak incidence was found to occur at age 5-9 years in the girls and 10-14 years in the boys. Mean age at diagnosis was 8.1±3.8 years. Rate of presentation with diabetic ketoacidosis was 65.9%. Patients applied most frequently in spring and winter months.

CONCLUSIONS

In this first T1DM incidence study on the pediatric age group in Diyarbakir, Turkey, T1DM incidence was found to be similar to that in countries with low-middle incidence.

The microbiology of human hygiene and its impact on type 1 diabetes

The incidence of type 1 diabetes (T1D), as with several other autoimmune diseases and conditions, began to notably rise in the latter half of the last century. Most cases of T1D are not solely attributable to genetics and therefore, environmental influences are proposed to account for the difference. Humans live today in general under much more hygienic conditions than their ancestors. Although human enteroviruses (HEV) have been strongly implicated as causative environmental agents of T1D, recent work has shown that the bacterial genera in the gut of diabetics compared with non-diabetics, can vary significantly. Here, we consider these data in light of our non-hygienic human past in order to discuss a possible relationship between the resident bacterial biome and acute infectious events by HEV, suggesting how this may have influenced T1D incidences in the past and the risk for developing T1D today.

What is the key environmental trigger in type 1 diabetes--is it viruses, or wheat gluten, or both?

Prevention and treatment of type 1 diabetes is hampered by the fact that the key environmental trigger(s) of the disease is still unknown. Much of the data on this subject points to two possibilities, viruses and wheat gluten. Viruses appear to be involved as an etiological agent in some cases of type 1 diabetes, particularly in fulminant type 1 diabetes. Further analysis of the data suggests that viruses are not the sole trigger of type 1 diabetes in humans, and that wheat gluten may play a role in initiating the disease. Viruses may be the key environmental trigger in some cases of type 1 diabetes, and wheat gluten in others. Conceivably, some cases of type 1 diabetes might be caused by viruses and wheat gluten acting together as disease triggers.

Creating a national register of childhood type 1 diabetes using routinely collected hospital data

INTRODUCTION

There is no national register of childhood type 1 diabetes mellitus for England. Our aim was to assess the feasibility of using routine hospital admissions data as a surrogate for a childhood diabetes register across England, and to create a geographically referenced childhood diabetes dataset for use in epidemiologic studies and health service research.

METHODS

Hospital Episodes Statistics data for England from April 1992 to March 2006 referring to a type 1 diabetes diagnosis in 0-14 yr olds were cleaned to approximate an incident dataset. The cleaned data were validated against regional population-based register data, available for Yorkshire and the area of the former Oxford Regional Health Authority.

RESULTS

There were 32 665 unique cases of type 1 and type unknown diabetes over the study period. The hospital-derived data improved in quality over time (91% concordance with regional register data over the period 2000-2006 vs. 52% concordance over the period 1992-1999), and data quality was better for younger (0-9 yr) (86.5% concordance with regional register data) than older cases (10-14 yr). Overall incidence was 24.99 (95% confidence interval 24.71-25.26) per 100 000. Basic trends in age distribution, seasonality of onset, and incidence matched well with previously reported findings.

CONCLUSION

We were able to create a surrogate register of childhood diabetes based on national hospital admissions data, containing approximately 2300 cases/yr, and geo-coded to a high resolution. For younger cases (0-9 yr) and more recent years (from 2000) these data will be a useful resource for epidemiological studies exploring the determinants of childhood diabetes.

Prevalence of type 1 diabetes mellitus in 6-18-yr-old school children living in Istanbul, Turkey

BACKGROUND

Type 1 diabetes mellitus (T1DM) is among the most common chronic diseases in childhood and the incidence of T1DM is increasing worldwide. There is no actual data regarding the frequency of T1DM in Turkish children.

OBJECTIVES

We aimed to assess current prevalence of T1DM in 6-18-yr-old school children living in Istanbul.

METHODS

Total number of students and children on insulin treatment were reported by the schools, as the first part of the study. At the second step, the study team visited 203 schools for confirmation of the reported data.

RESULTS

One thousand and ninety children in a population of 1 630 751 school children were reported to have T1DM, which made the total prevalence of T1DM 0.67/1000 (95% confidence interval 0.6/1000-0.7/1000). A population of 217 030 children (α=0.05 and β=0.20) from 203 schools were screened. The difference between the reported and detected prevalence was 0.032/1000 (215 detected vs. 222 reported, p>0.05). Comparison of the current data with the prevalence reported in a smaller population in Ankara, Turkey, 16 yr ago, demonstrated that the prevalence of T1DM is higher in the current study (0.46/1000 vs. 0.16/1000, 0.57/1000 vs. 0.34/1000, and 0.92/1000 vs. 0.69/1000 at primary, secondary, and high schools, respectively).

CONCLUSION

This first pediatric T1DM prevalence data in a large pediatric population in Istanbul, Turkey, estimated the prevalence of T1DM as 0.67/1000. This prevalence is 2.5-fold higher than that reported in Ankara, Turkey, in 1993, suggesting that T1DM prevalence is increasing in Turkey as in the other parts of the world.

Association analysis of proopiomelanocortin (POMC) haplotypes in type 1 diabetes in a UK population

AIM

To assess the association of POMC haplotype-tagged single nucleotide polymorphisms (htSNPs) with the development of type 1 diabetes (T1D) in a Caucasian population.

METHODS

All exons, intron 1, and approximately 6-kb upstream and 3-kb downstream of the POMC gene were bidirectionally resequenced to identify DNA polymorphisms in 30 individuals. Allele frequencies were determined (60 chromosomes) and efficient htSNPs were selected using the htSNP2 programme. Genotyping was performed in 390 cases, 339 controls and 245 T1D parent-offspring trios, using Taqman, Sequenom and direct-sequencing technologies.

RESULTS

Thirteen polymorphisms (two novel) with a minor allele frequency greater than 1% were identified. Six POMC htSNPs (rs3754863 G>A, ss161151662 A>G, rs3754860 C>T, rs1009388 G>C, rs3769671 A>C, rs1042571 G>A) were identified. Allele and haplotype frequencies were similar between case and control groups (P>0.60 by permutation test), and assessment of allele transmission distortion from informative parents to affected offspring also failed to find any association. Stratification of these analyses for age-at-onset and HLA-DR risk group (DR3/DR4) revealed no significant associations. A haplotype block of 9.86-kb from rs3754863 to rs1042571 was identified, encompassing the POMC gene. Comparison of haplotype frequencies identified the GGCGAG haplotype as protective against T1D in 12.9% of cases vs. 18.3% of controls: χ(2)=8.18, Pc=0.03 by permutation test.

CONCLUSION

The POMC SNP haplotype GGCGAG may have a protective effect against T1D in the UK population. However, this finding needs to be replicated, and the cellular and molecular processes influenced by this POMC haplotype determined to fully appreciate its impact.

Low zinc in drinking water is associated with the risk of type 1 diabetes in children

AIM

To explore if drinking water may influence the development of type 1 diabetes in children, either via enterovirus spread via drinking water or quality of drinking water related to acidity or concentration of certain minerals.

METHODS

One hundred and forty-two families with a child with diabetes and who lived either in seven municipalities with a high annual diabetes incidence during 1977-2001 and in six municipalities with the lowest incidence during those 25 yr were asked to participate. Three hundred and seventy-three families in these communities were used as controls. The families filled a 200-mL plastic bottle with their tap drinking water and returned it by mail. The water samples were analyzed for pH, zinc, iron, nitrate, nitrite, nitrate-nitrogen and nitrite-nitrogen, and occurrence of enterovirus RNA.

RESULTS

Enterovirus RNA was not found in the tap water samples. The concentration of zinc, nitrate, and nitrate-nitrogen was lower in the municipalities with high incidence of type 1 diabetes. The water samples from families with a child with diabetes had lower concentration of zinc than water samples from control families.

CONCLUSION

Low zinc in drinking water is associated with the risk of developing type 1 diabetes during childhood. Enterovirus does not seem to be spread via drinking water in a country with modern water works.

Reduced expression of IFIH1 is protective for type 1 diabetes

IFIH1 (interferon induced with helicase C domain 1), also known as MDA5 (melanoma differentiation-associated protein 5), is one of a family of intracellular proteins known to recognise viral RNA and mediate the innate immune response. IFIH1 is causal in type 1 diabetes based on the protective associations of four rare variants, where the derived alleles are predicted to reduce gene expression or function. Originally, however, T1D protection was mapped to the common IFIH1 nsSNP, rs1990760 or Thr946Ala. This common amino acid substitution does not cause a loss of function and evidence suggests the protective allele, Ala(946), may mark a haplotype with reduced expression of IFIH1 in line with the protection conferred by the four rare loss of function alleles. We have performed allele specific expression analysis that supports this hypothesis: the T1D protective haplotype correlates with reduced IFIH1 transcription in interferon-β stimulated peripheral blood mononuclear cells (overall p = 0.012). In addition, we have used multiflow cytometry analysis and quantitative PCR assays to prove reduced expression of IFIH1 in individuals heterozygous for three of the T1D-associated rare alleles: a premature stop codon, rs35744605 (Glu627X) and predicted splice variants, rs35337543 (IVS8+1) and rs35732034 (IVS14+1). We also show that the nsSNP, Ile923V, does not alter pre-mRNA levels of IFIH1. These results confirm and extend the new autoimmune disease pathway of reduced IFIH1 expression and protein function protecting from T1D.

Environmental factors associated with childhood-onset type 1 diabetes mellitus: an exploration of the hygiene and overload hypotheses

OBJECTIVE

To assess the relationship between selected maternal and infant characteristics and risk of type 1 diabetes mellitus, specifically characteristics identified from birth records that may pertain to the hygiene or overload hypotheses.

DESIGN

Population-based case-control study.

SETTING

Washington State from 1987 to 2005.

PARTICIPANTS

All children younger than 19 years hospitalized for type 1 diabetes (International Classification of Diseases, Ninth Revision codes 250.x1 and 250.x3) identified (n=1852) from hospital discharge data and linked with their birth certificates. Controls (n=7408) were randomly selected from birth records, frequency matched on year of birth.

MAIN EXPOSURES

Maternal factors included age, race, educational attainment, marital status, use of Medicaid insurance, body mass index, prepregnancy weight, prior births, timing and adequacy of prenatal care, and cesarean delivery. Infant factors included birth weight, size for gestational age, and gestational age.

MAIN OUTCOME MEASURE

The main outcome was first hospitalization for type 1 diabetes mellitus; adjusted odds ratios were estimated for the association of selected maternal and infant characteristics with type 1 diabetes.

RESULTS

Consistent with the hygiene hypothesis, type 1 diabetes was negatively associated with having older siblings (for >or=3 siblings, odds ratio [OR], 0.56; 95% confidence interval [CI], 0.45-0.70) and with indicators of lower economic status or care access, such as an unmarried mother (OR, 0.79; 95% CI, 0.69-0.91), inadequate prenatal care (OR, 0.53; 95% CI, 0.40-0.71), or Medicaid insurance (OR, 0.67; 95% CI, 0.58-0.77). Related to the overload hypothesis, maternal body mass index of 30 or higher (OR, 1.29; 95% CI, 1.01-1.64) was associated with increased risk of diabetes.

CONCLUSION

Environmental factors related to decreased antigenic stimulation in early life and maternal obesity may be associated with type 1 diabetes.

Enteroviruses, type 1 diabetes and hygiene: a complex relationship

Type 1 diabetes (T1D) is an autoimmune disease in which the immune system mounts an attack on the host's insulin‐producing β cells. Because most cases of T1D cannot be attributed only to individual genetics, it is strongly inferred that there is a significant environmental contribution, such as infection, impacting disease development. The human enteroviruses (HEV) are common picornaviruses often implicated as triggers of human T1D, although precisely which of the numerous HEV may be involved in human T1D development is unknown. Experiments using non‐obese diabetic (NOD) mice, commonly used to model T1D, show that induction of T1D by HEV infection in NOD mice is a multifactorial process involving both the virus and the host. Interestingly, results demonstrate that HEV infection of NOD mice can also induce long‐term protection from T1D under certain conditions, suggesting that a similar mechanism may occur in humans. Based upon both experimental animal and observational human studies, we postulate that HEV have a dual role in T1D development and can either cause or prevent autoimmune disease. Whichever outcome occurs depends upon multiple variables in the host‐virus equation, many of which can be deduced from results obtained from NOD mouse studies. We propose that the background to the sharply rising T1D incidences observed in the 20th century correlates with increased levels of hygiene in human societies. Viewing T1D in this perspective suggests that potential preventative options could be developed. Copyright © 2009 John Wiley & Sons, Ltd.

The 'hygiene hypothesis' for autoimmune and allergic diseases: an update

According to the 'hygiene hypothesis', the decreasing incidence of infections in western countries and more recently in developing countries is at the origin of the increasing incidence of both autoimmune and allergic diseases. The hygiene hypothesis is based upon epidemiological data, particularly migration studies, showing that subjects migrating from a low-incidence to a high-incidence country acquire the immune disorders with a high incidence at the first generation. However, these data and others showing a correlation between high disease incidence and high socio-economic level do not prove a causal link between infections and immune disorders. Proof of principle of the hygiene hypothesis is brought by animal models and to a lesser degree by intervention trials in humans. Underlying mechanisms are multiple and complex. They include decreased consumption of homeostatic factors and immunoregulation, involving various regulatory T cell subsets and Toll-like receptor stimulation. These mechanisms could originate, to some extent, from changes in microbiota caused by changes in lifestyle, particularly in inflammatory bowel diseases. Taken together, these data open new therapeutic perspectives in the prevention of autoimmune and allergic diseases.

Polymorphisms of the macrophage migration inhibitory factor gene in a UK population with Type 1 diabetes mellitus

AIMS

Macrophage migration inhibitory factor (MIF) is a potent pro-inflammatory cytokine whose production is transcriptionally regulated by glucose. Experimental data from both Type 1 diabetes mellitus (T1D) patients and animal models suggests a role for MIF in the development of T1D. The aim of this study was to employ gene resequencing to identify common DNA polymorphisms in the MIF gene and subsequently assess haplotype tagged single nucleotide polymorphisms (htSNPs) using a combination of case-control and family-based association analyses in order to assess the association of MIF htSNPs with the development of T1D in a white population.

METHODS

All exons, introns and approximately 3 kb upstream and downstream of the MIF gene were screened for DNA polymorphisms in 46 individuals using DNA sequencing. Genotyping of the htSNPs was performed in 432 cases, 407 control subjects and 290 T1D parent-offspring trios, using Taqman, Sequenom, Pyrosequencing and fluorescence-based microsatellite technologies.

RESULTS

Twenty-three polymorphisms (two novel) with a minor allele frequency > 10% were identified. Four MIF htSNPs (rs875643 G>A, rs7388067 C>T, rs5844572 -/CATT, rs6003941 T>G) were identified. Allele and haplotype frequencies were similar between case and control groups (P > 0.6 by permutation test) and assessment of allele transmission distortion from informative parents to affected offspring also failed to find an association. Stratification of these analyses for age-at-onset and human leukocyte antigen (HLA)-DR risk group (DR3/DR4) did not reveal any significant associations.

CONCLUSIONS

It is unlikely that common polymorphisms in the MIF gene strongly influence susceptibility to T1D in the UK population.

Evaluating geographic variation in type 1 and type 2 diabetes mellitus incidence in youth in four US regions

We evaluated geographic variation in type 1 and type 2 diabetes mellitus (T1DM, T2DM) in four regions of the United States. Data on 807 incident T1DM cases diabetes and 313 T2DM cases occurring in 2002-03 in South Carolina (SC) and Colorado (CO), 5 counties in Washington (WA), and an 8 county region around Cincinnati, Ohio (OH) among youth aged 10-19 years were obtained from the SEARCH for Diabetes in Youth Study. Geographic patterns were evaluated in a Bayesian framework. Incidence rates differed between the study regions, even within race/ethnic groups. Significant small-area variation within study region was observed for T1DM and T2DM. Evidence for joint spatial correlation between T1DM and T2DM was present at the county level for SC (r(SC)=0.31) and CO non-Hispanic Whites (r(CO)=0.40) and CO Hispanics (r(CO)=0.72). At the tract level, no evidence for meaningful joint spatial correlation was observed (r(SC)=-0.02; r(CO)=-0.02; r(OH)=0.03; and r(WA=)0.09). Our study provides evidence for the presence of both regional and small area, localized variation in type 1 and type 2 incidence among youth aged 10-19 years in the United States.

The geoepidemiology of type 1 diabetes

Type 1 diabetes (T1D) is a chronic autoimmune disease characterized by absolute insulin deficiency resulting from the progressive immune-mediated destruction of pancreatic islet beta cells. It is thought to be triggered by as yet unidentified environmental factors in genetically susceptible individuals, the major genetic contribution coming from loci within the HLA complex, in particular HLA class II. The worldwide incidence of T1D varies by at least 100-fold, being highest in Finland and Sardinia (Italy) and lowest in Venezuela and China. The incidence has been increasing worldwide at an annual rate of approximately 3%. While genetic factors are thought to explain some of the geographic variability in T1D occurrence, they cannot account for its rapidly increasing frequency. Instead, the declining proportion of newly diagnosed children with high-risk genotypes suggests that environmental pressures are now able to trigger T1D in genotypes that previously would not have developed the disease during childhood. Although comparisons between countries and regions with low and high-incidence rates have suggested that higher socioeconomic status and degree of urbanization are among the environmental factors that play a role in the rising incidence of T1D, the findings are too inconsistent to allow firm conclusions. Morbidity and mortality as well as causes of death also show considerable geographic variation. While glycemic control has been identified as a major predictor of the micro- and macrovascular complications of T1D and shows considerable geographical variability, it does not appear to be the only factor involved in the regional differences in complication rates. The role of genetics in susceptibility to nephropathy, retinopathy and other diabetic complications largely remains to be explored.

Long-term trends in the incidence of type 1 diabetes in Denmark: the seasonal variation changes over time

There is a worldwide increase of type 1 diabetes mellitus (T1DM). In 1996, the Danish population-based registry was initiated including all newly diagnosed children aged 0-15 yr. This is the report of incidence and seasonal variation for the first 10 yr of the registry. The data was analyzed using Poisson's regression analysis. A total of 2166 children with diabetes were diagnosed before the age of 15 yr between 1996 and 2005. In this period, the annual increase in childhood T1DM was 3.43% (95% confidence interval: 1.91-4.97), which was unaffected by age and gender. Seasonal variation in incidence rates varied by year but not by age and gender. In conclusion, there is a steep increase in incidence of childhood T1DM in Denmark; the increase is comparable with the increase seen in other European countries. There is a significant seasonal variation that changes on a year-to-year basis. The observed variations in cadence rates may be associated with viral epidemics, sunshine exposure, or vitamin D levels and suggest further exploration of these relations.

Infection and type 1 diabetes mellitus - a two edged sword?

Infection by various viral and bacterial pathogens has long been proposed as one of the etiologies of autoimmune diabetes. Many theories, ranging from direct cytolysis of pancreatic islet cells to immunological processes such as antigen mimicry and polyclonal lymphocyte activation, tried to explain the epidemiological correlation between infections and diabetes, supported by information from human and animal studies. However, a direct correlation and exact mechanism continue to elude investigators due to scarce and conflicting data. Interestingly, there is also data to support an opposite role for infection in the development of type 1 diabetes, as several pathogens demonstrated a protective effect from this disease. This article reviews the current data available from clinical studies and animal models, while trying to explain the different mechanisms underlying these findings.

Variations in incidence of type 1 diabetes in different municipalities of stockholm

This article reports a test of the hypothesis that municipalities within the County of Stockholm have varying incidence rates of type 1 diabetes (T1D), suggesting a strong etiologic environmental component to the disease. The study group included T1D patients in the age group from birth to 18 years who were diagnosed each year from 20 municipalities in Stockholm County during the 1990-2003. Specific incidence rates by age, sex, and socioeconomic characteristics (income level, proportion of taxpayers, proportion of foreigners, population density and green cover) were estimated annually together with age standardization. chi(2) analyses were used for the statistical assessment of variability in incidence. During the study period, 733 newly diagnosed T1D patients aged 0-18 years were recorded from the 20 municipalities under study. The overall age-standardized incidence in these 20 municipalities was 24.38 (22.65-26.21) per 100,000, with 45.35 (32.08-62.29) as highest and 13.41 (9.53-18.35) as lowest estimated incidence. For all socioeconomic variables statistically significant heterogeneity was demonstrated in the standardized incidence rate. High green index was positively associated with the incidence of T1D, as was low population density. For the three remaining socioeconomic variables no clear patterns of associations with incidence of T1D were seen. This study demonstrates a considerable and statistically significant variation between the lowest and highest values in the incidence and prevalence rates for T1D in municipalities of Stockholm County. Such variation seems unlikely to be explained by genetic differences since the population is homogeneous. Our study provides support for the hypothesis that environmental factors have a major influence on the pathogenesis of T1D.

Epidemiology of type 1 diabetes and what animal models teach us about the role of viruses in disease mechanisms

There is a consensus among epidemiologists that the worldwide incidence rate of type 1 diabetes has been rising in recent decades. The cause of this rise is unknown, but epidemiological studies suggest the involvement of environmental factors, and viral infections in particular. Data demonstrating a cause-and-effect relationship between microbial infections and type 1 diabetes and how viruses may cause disease in humans are currently lacking. However, new evidence from animal models supports the hypothesis that viruses induce disease via mechanisms linked with innate immune upregulation. In the BioBreeding Diabetes Resistant rat, infection with a parvovirus induces islet destruction via upregulation of the toll-like receptor 9 (TLR9) signaling pathway. Data from mouse models of diabetes implicate TLR2, TLR3, and TLR7 in the disease process. Understanding the link between environmental agents and innate immune pathways involved in early stages of diabetes may advance the design of immune interventions to prevent disease in genetically susceptible individuals.

[Controversies in the association between type 1 diabetes and asthma]

OBJECTIVE

Critical review of the literature to investigate the relationship between asthma and type 1 diabetes mellitus (DM1).

SOURCE OF DATA

Bibliography search in MEDLINE and LILACS databases in the last twenty years.

SUMMARY OF DATA

Several studies demonstrate an inverse relationship between asthma, atopic diseases and the risk to develop DM1. According to the "Hygiene Hypothesis", the risk of allergic diseases decreases with infections early in childhood, towards distance of Th2 profile, common at birth, to the Th1 phenotype. Other articles described lack of association or positive association between DM1 and allergies. There is a possibility of environmental factors interfering in the development of disorders mediated by Th1 and Th2 cells, in the same individual, due to the absence of immunomodulatory mechanisms mediated by interleukin-10 and regulatory cells.

CONCLUSION

The existing information about the inverse association between Th1-mediated diseases (e.g., DM1), and those that are Th2-mediated (e.g., allergies) are conflicting requiring more investigation to explain this question.

A low incidence of Type 1 diabetes between 1977 and 2001 in south-eastern Sweden in areas with high population density and which are more deprived

AIMS

To explore how socioeconomic factors and population density may contribute to the geographical variation of incidence of Type 1 diabetes in children in south-eastern Sweden.

METHOD

All children diagnosed with Type 1 diabetes in south-eastern Sweden during 1977-2001 were defined geographically to their place of residence and were allocated x and y coordinates in the national grid. The population at risk and socioeconomic data were aggregated in 82,000 200-m squares and geocoded likewise. A socioeconomic index was calculated using a signed chi(2) method. Rural-urban gradients were defined by overlay analysis in a geographic information system.

RESULTS

The incidence during the past 25 years has been rising steadily, particularly in the last 6 years. The incidence was highest in areas with a high proportion of small families, of families with a high family income and better education, and this was found both at the time of diagnosis and at the time of birth. In the rural-urban analysis, the lowest incidence was found in the urban area with > 20,000 inhabitants, where there was also a higher frequency of deprivation.

CONCLUSIONS

Our findings indicate that geographical variations in incidence rates of Type 1 diabetes in children are associated with socioeconomic factors and population density, although other contributing factors remain to be explained.

Changing geographical distribution of diabetes mellitus type 1 incidence in Austrian children 1989--2005

OBJECTIVES

We investigated whether the significant spatial West/East trend of incidence of Diabetes mellitus Type 1 in Austrian children changed between 1989 and 2005. Additionally we tested, whether population density and mean body mass index of newborns is associated with incidence.

STUDY DESIGN AND SETTING

All newly diagnosed cases aged 0-14 years in Austria (n = 2644), prospectively registered from 1989 to 2005 were allocated to 99 districts. Ecological regression and analysis was done by Bayesian hierarchical models including spatially correlated risks.

RESULTS

In Austria, the incidence rose from 9.1/100.000 in 1989--1994 to 14.9/100.000 in 2001--2005. The spatial trend in the period 1989--1995, showing high incidence in the Eastern parts of Austria, disappeared. In the period 2001--2005 a significant inverse negative association of population density with incidence was found. Mean body mass index of newborns in the Austrian population is significantly positively associated with incidence.

CONCLUSION

The observation of higher incidence in rural areas in Austria during recent years may reflect a lower exposure to protective environmental factors, e.g. infections early in life. The observed association with the BMI in newborns indicates that neonatal or prenatal metabolic aspects may modulate the risk for childhood diabetes. We cannot explain the change in the spatial distribution of incidence.

The candidate genes TAF5L, TCF7, PDCD1, IL6 and ICAM1 cannot be excluded from having effects in type 1 diabetes

BACKGROUND

As genes associated with immune-mediated diseases have an increased prior probability of being associated with other immune-mediated diseases, we tested three such genes, IL23R, IRF5 and CD40, for an association with type 1 diabetes. In addition, we tested seven genes, TAF5L, PDCD1, TCF7, IL12B, IL6, ICAM1 and TBX21, with published marginal or inconsistent evidence of an association with type 1 diabetes.

METHODS

We genotyped reported polymorphisms of the ten genes, nonsynonymous SNPs (nsSNPs) and, for the IL12B and IL6 regions, tag SNPs in up to 7,888 case, 8,858 control and 3,142 parent-child trio samples. In addition, we analysed data from the Wellcome Trust Case Control Consortium genome-wide association study to determine whether there was any further evidence of an association in each gene region.

RESULTS

We found some evidence of associations between type 1 diabetes and TAF5L, PDCD1, TCF7 and IL6 (ORs = 1.05 - 1.13; P = 0.0291 - 4.16 x 10-4). No evidence of an association was obtained for IL12B, IRF5, IL23R, ICAM1, TBX21 and CD40, although there was some evidence of an association (OR = 1.10; P = 0.0257) from the genome-wide association study for the ICAM1 region.

CONCLUSION

We failed to exclude the possibility of some effect in type 1 diabetes for TAF5L, PDCD1, TCF7, IL6 and ICAM1. Additional studies, of these and other candidate genes, employing much larger sample sizes and analysis of additional polymorphisms in each gene and its flanking region will be required to ascertain their contributions to type 1 diabetes susceptibility.

Large-scale genetic fine mapping and genotype-phenotype associations implicate polymorphism in the IL2RA region in type 1 diabetes

Genome-wide association studies are now identifying disease-associated chromosome regions. However, even after convincing replication, the localization of the causal variant(s) requires comprehensive resequencing, extensive genotyping and statistical analyses in large sample sets leading to targeted functional studies. Here, we have localized the type 1 diabetes (T1D) association in the interleukin 2 receptor alpha (IL2RA) gene region to two independent groups of SNPs, spanning overlapping regions of 14 and 40 kb, encompassing IL2RA intron 1 and the 5' regions of IL2RA and RBM17 (odds ratio = 2.04, 95% confidence interval = 1.70-2.45; P = 1.92 x 10(-28); control frequency = 0.635). Furthermore, we have associated IL2RA T1D susceptibility genotypes with lower circulating levels of the biomarker, soluble IL-2RA (P = 6.28 x 10(-28)), suggesting that an inherited lower immune responsiveness predisposes to T1D.