A case-control investigation of perinatal risk factors for childhood IDDM in Northern Ireland and Scotland

Is socio-economic status associated with risk of childhood type 1 diabetes? Literature review

AIMS

Studies of social inequality and risk of developing type 1 diabetes are inconsistent. The present review aimed to comprehensively review relevant literature and describe what has been reported on socio-economic status or parental occupation and risk of type 1 diabetes in children.

METHODS

We searched for publications between 1 January 1970 and 30 November 2021. We focused on the most recent and/or informative publication in cases of multiple publications from the same data source and referred to these as primary studies.

RESULTS

Our search identified 69 publications with relevant data. We identified eight primary cohort studies with individual-level data, which we considered the highest quality of evidence. Furthermore, we identified 13 primary case-control studies and 14 semi-ecological studies with area-level socio-economic status variables which provided a weaker quality of evidence. Four of eight primary cohort studies contained data on maternal education, showing non-linear associations with type 1 diabetes that were not consistent across studies. There was no consistent pattern on the association of parental occupation and childhood-onset type 1 diabetes.

CONCLUSIONS

There is a need for more high-quality studies, but the existing literature does not suggest a major and consistent role of socio-economic status in the risk of type 1 diabetes.

The Association Between High Birth Weight and Long-Term Outcomes-Implications for Assisted Reproductive Technologies: A Systematic Review and Meta-Analysis

Background: Studies have shown that the prevalence of children born with high birth weight or large for gestational age (LGA) is increasing. This is true for spontaneous pregnancies; however, children born after frozen embryo transfer (FET) as part of assisted reproductive technology (ART) also have an elevated risk. In recent years, the practice of FET has increased rapidly and while the perinatal and obstetric risks are well-studied, less is known about the long-term health consequences. Objective: The aim of this systematic review was to describe the association between high birth weight and LGA on long-term child outcomes. Data Sources: PubMed, Scopus, and Web of Science were searched up to January 2021. Exposure included high birth weight and LGA. Long-term outcome variables included malignancies, psychiatric disorders, cardiovascular disease, and diabetes. Study Selection: Original studies published in English or Scandinavian languages were included. Studies with a control group were included while studies published as abstracts and case reports were excluded. Data Extraction: The methodological quality, in terms of risk of bias, was assessed by pairs of reviewers. Robins-I (www.methods.cochrane.org) was used for risk of bias assessment in original articles. For systematic reviews, AMSTAR (www.amstar.ca) was used. For certainty of evidence, we used the GRADE system. The systematic review followed PRISMA guidelines. When possible, meta-analyses were performed. Results: The search included 11,767 articles out of which 173 met the inclusion criteria and were included in the qualitative analysis, while 63 were included in quantitative synthesis (meta-analyses). High birth weight and/or LGA was associated with low to moderately elevated risks for certain malignancies in childhood, breast cancer, several psychiatric disorders, hypertension in childhood, and type 1 and 2 diabetes. Conclusions: Although the increased risks for adverse outcome in offspring associated with high birth weight and LGA represent serious health effects in childhood and in adulthood, the size of these effects seems moderate. The identified risk association should, however, be taken into account in decisions concerning fresh and frozen ART cycles and is of general importance in view of the increasing prevalence in high birthweight babies.

Targeting Glycoproteins as a therapeutic strategy for diabetes mellitus and its complications

OBJECTIVES

Glycoproteins are organic compounds formed from proteins and carbohydrates, which are found in many parts of the living systems including the cell membranes. Furthermore, impaired metabolism of glycoprotein components plays the main role in the pathogenesis of diabetes mellitus. The aim of this study is to investigate the influence of glycoprotein levels in the treatment of diabetes mellitus.

METHODS

All relevant papers in the English language were compiled by searching electronic databases, including Scopus, PubMed and Cochrane library. The keywords of glycoprotein, diabetes mellitus, glycan, glycosylation, and inhibitor were searched until January 2019.

RESULTS

Glycoproteins are pivotal elements in the regulation of cell proliferation, growth, maturation and signaling pathways. Moreover, they are involved in drug binding, drug transportation, efflux of chemicals and stability of therapeutic proteins. These functions, structure, composition, linkages, biosynthesis, significance and biological effects are discussed as related to their use as a therapeutic strategy for the treatment of diabetes mellitus and its complications.

CONCLUSIONS

The findings revealed several chemical and natural compounds have significant beneficial effects on glycoprotein metabolism. The comprehension of glycoprotein structure and functions are very essential and inevitable to enhance the knowledge of glycoengineering for glycoprotein-based therapeutics as may be required for the treatment of diabetes mellitus and its associated complications. Graphical abstract.

The effect of microbiome exposure at birth on pediatric outcomes using a twin cohort discordant for microbiome exposure at birth

Objective: Microbiome exposure at birth has been associated with long-term pediatric outcomes. However, it is difficult to determine if differences in outcomes are truly due to microbiome exposure at birth or other exposures after birth and in early infancy. Using a twin cohort, we sought to determine the association between length of exposure to the maternal vaginal-fecal microbiome and long-term pediatric health outcomes by comparing outcomes between presenting and nonpresenting twins born to women who labored.Methods: We performed a mail-based survey study of women in a single maternal-fetal medicine practice who delivered twin pregnancies ≥24 weeks. The survey study was sent to women when twins were between 2 and 10 years old to assess the long-term health outcomes, including any medical diagnoses or problems with grown and development. For this study, we included all women who labored, and we compared health outcomes for the presenting versus nonpresenting twin with the primary outcome being the development of asthma/reactive airway disease and allergies. The length of exposure to the maternal vaginal-fecal microbiome was measured using the time from rupture of membranes (ROM) to delivery of each twin. Chi-square and Student's t-test were used.Results: Two hundred fifty-seven sets of twins were eligible for analyses. The presenting twin had a longer time of ROM than the nonpresenting twin (617 ± 2408 min versus 2 ± 5 minutes, p < .001). There were no significant differences between health outcomes for the presenting versus nonpresenting twin in the overall cohort, including the development of asthma/reactive airway disease (9.3 versus 10.1%, p = .77) or allergies (12.5 versus 7.8%, p = .08). There were no differences in any outcomes when comparing the presenting versus nonpresenting twin for those twins delivered vaginally or by cesarean delivery.Conclusion: In twins born to women who labored and either delivered vaginally or via cesarean section, delivery order was not associated with any significant increase in defined adverse pediatric outcomes, including the development of asthma or allergies. Using twins as a model for microbiome exposure may help to elucidate the role of the maternal vaginal-fecal microbiome on long-term pediatric health outcomes.

Risk of Type 1 Diabetes in the Offspring Born through Elective or Non-elective Caesarean Section in Comparison to Vaginal Delivery: a Meta-Analysis of Observational Studies

BACKGROUND

Caesarean section (CS) has been associated with an increased risk of type 1 diabetes (T1D). The lack of exposure to maternal vaginal and anal microbiome and bypassing the labor process often observed in elective CS may affect neonatal immune system development. This study aims to summarize the effects of elective and non-elective CS on T1D risk in the offspring.

METHODS

A systematic literature search was conducted online for publications providing data on elective and non-elective CS with T1D diagnosis in children and young adults, followed by a meta-analysis from selected studies. Newcastle-Ottawa Scale and GRADEpro tool were applied for quality analysis.

RESULTS

Nine observational studies comprising over 5 million individuals fulfilled the inclusion criteria. Crude OR estimates showed a 12% increased T1D risk from elective CS compared to vaginal delivery with significant heterogeneity. Adjusted ORs from seven studies did not show T1D risk differences from either CS category, and heterogeneity was detected between studies. Separate analysis of cohort and case-control studies reduced the heterogeneity and revealed a slight increase in T1D risk associated with elective CS in cohort studies (adjusted OR = 1.12 (1.01-1.24)), and a higher increased risk associated with non-elective CS in case-control studies (adjusted OR = 1.19 (1.06-1.34)).

CONCLUSION

Summarized crude risk estimates showed a small increased T1D risk in children and young adults born through elective CS compared to vaginal delivery, but with significant heterogeneity. Adjusted risk estimates by study design indicated a slightly increased T1D risks associated with elective or non-elective CS.

Stem-cell based organ-on-a-chip models for diabetes research

Diabetes mellitus (DM) ranks among the severest global health concerns of the 21st century. It encompasses a group of chronic disorders characterized by a dysregulated glucose metabolism, which arises as a consequence of progressive autoimmune destruction of pancreatic beta-cells (type 1 DM), or as a result of beta-cell dysfunction combined with systemic insulin resistance (type 2 DM). Human cohort studies have provided evidence of genetic and environmental contributions to DM; yet, these studies are mostly restricted to investigating statistical correlations between DM and certain risk factors. Mechanistic studies, on the other hand, aimed at re-creating the clinical picture of human DM in animal models. A translation to human biology is, however, often inadequate owing to significant differences between animal and human physiology, including the species-specific glucose regulation. Thus, there is an urgent need for the development of advanced human in vitro models with the potential to identify novel treatment options for DM. This review provides an overview of the technological advances in research on DM-relevant stem cells and their integration into microphysiological environments as provided by the organ-on-a-chip technology.

Prevalence of early and late prematurity is similar among pediatric type 1 diabetes patients and the general population

BACKGROUND

The incidence of type 1 diabetes mellitus (T1DM) has increased in recent decades, as has the incidence of preterm births (<37 weeks). We aimed to evaluate and compare the prevalence of prematurity and early prematurity (<34 weeks) and birth season variability among T1DM and non-T1DM children.

METHODS

A nationwide cross-sectional study was conducted, with linkage of data from 13 paediatric diabetes centers and Israeli National Registries, including T1DM patients and general non-T1DM population, born during 2000 to 2013. Gathered data included ethnicity, gender, birth week, weight, and season. The prevalence of prematurity and birth season were compared with the general population birth registry using Pearson Chi-square test.

RESULTS

The study population included 1452 T1DM patients, 52.7% males, and 2 138 668 subjects in the general non-T1DM population, 51.2% males. The prevalence of late and early prematurity was similar between groups (6.1% and 2.2% in the T1DM group vs 5.6% and 2.0% in the general non-T1DM group, P = 0.25 and P = 0.38, respectively). OR for prematurity among T1DM patients was 1.15 (0.95-1.39), P = 0.16. No difference in birth season was demonstrated between preterm and term, in T1DM and general non-T1DM populations. Ethiopian descent was more prevalent among T1DM patients compared with the non-T1DM population, in both term and preterm born.

CONCLUSIONS

This is the largest population-based study, and the first in the Middle East geographical area, indicating that prematurity, including early prematurity, is not associated with T1DM during childhood. The study was registered at https://clinicaltrials.gov/: NCT02929953.

Prelabor Cesarean Section and Risk of Childhood Type 1 Diabetes: A Nationwide Register-based Cohort Study

BACKGROUND

Unfavorable conditions associated with cesarean section may influence the risk of type 1 diabetes in offspring, but results from studies are conflicting. We aimed to evaluate the association between prelabor cesarean section and risk of childhood type 1 diabetes.

METHODS

A Danish nationwide cohort study followed all singletons born during 1982-2010. Four national registers provided information on mode of delivery, outcome, and confounders. The risk of childhood type 1 diabetes with onset before the age of 15 years was assessed by Cox regression. A total of 1,760,336 singletons contributed 20,436,684 person-years, during which 4,400 were diagnosed with childhood type 1 diabetes.

RESULTS

The hazard ratio (HR) for childhood type 1 diabetes was increased in children delivered by prelabor cesarean section compared with vaginal delivery when adjusted for year of birth, parity, sex, parental age, and education and paternal type 1 diabetes status at childbirth (HR = 1.2; 95% confidence interval [CI] = 1.0, 1.3), but not after additional adjustment for maternal type 1 diabetes status at childbirth (HR = 1.1; 95% CI = 0.95, 1.2). Delivery by intrapartum cesarean section was not associated with childhood type 1 diabetes. Paternal type 1 diabetes was a stronger risk factor for childhood type 1 (HR = 12; 95% CI = 10, 14) than maternal type 1 diabetes (HR = 6.5; 95% CI = 5.2, 8.0).

CONCLUSIONS

Delivery by prelabor cesarean section was not associated with an increased risk of childhood type 1 diabetes in the offspring.

Preterm birth and risk of type 1 and type 2 diabetes: systematic review and meta-analysis

Preterm birth is suggested to play an important role in the development of diabetes. However, results have been inconsistent. We conducted a systematic review and meta-analysis to clarify the relationship between preterm birth and type 1 and type 2 diabetes. PubMed, Embase and ISI Web of Science were searched. A total of 18 studies (including 2,176,480 participants and 22,073 cases) for type 1 diabetes and five studies (including 31,478 participants and 1,898 cases) for type 2 diabetes were included in the current meta-analyses. We calculated pooled odds ratio (OR) and 95% confidence interval (CI) using fixed-effects model to evaluate the relations between preterm birth and type 1 and type 2 diabetes. The results suggested that preterm birth was significantly associated with increased risk of type 1 diabetes (OR = 1.18, 95% CI = 1.11-1.25), with no evidence of between-study heterogeneity (I(2) = 13.2%, P = 0.296). Preterm birth was also significantly associated with increased risk of type 2 diabetes (OR = 1.51, 95% CI = 1.32-1.72), with no evidence of (I(2) = 0.0%, P = 0.557). Subgroup analyses suggested that there was significant association in both case-control studies (OR = 1.16, 95% CI = 1.06-1.26) and cohort studies (relative risk = 1.20, 95% CI = 1.11-1.29) for type 1 diabetes, and similar results were found for type 2 diabetes. The results suggested that preterm birth was a significant and independent risk factor for both type 1 and type 2 diabetes.

Mode of obstetrical delivery and type 1 diabetes: a sibling design study

OBJECTIVES

We investigated the association between cesarean section (CS) and type 1 diabetes (T1D), and if the association remains after accounting for familial confounding by using a sibling-control design.

METHODS

We conducted a population-based cohort study of all singleton live births in Sweden between 1982 and 2009, followed by sibling-control analyses. T1D diagnoses were identified from the Swedish National Patient Register. Mode of delivery was categorized into unassisted vaginal delivery (reference group), instrumental vaginal delivery (IVD), emergency CS, and elective CS. The statistical analysis was conducted in 2 steps: firstly log-linear Poisson regression with aggregated person-years by using the full cohort; secondly, conditional logistic regression for sibling-control analyses. The sibling analysis included siblings who were discordant for both mode of delivery and T1D.

RESULTS

In the cohort analyses (N = 2 638 083), there was an increased risk of childhood T1D among children born by elective CS (adjusted relative risk [RR] = 1.15 [95% confidence interval: 1.06-1.25]) and IVD (RR=1.14 [1.06-1.23]) but not emergency CS (RR = 1.02 [0.95-1.11]) when compared with children born by unassisted vaginal birth. However, the effect of elective CS and IVD on childhood T1D almost disappeared and became nonsignificant in the sibling-control analyses.

CONCLUSIONS

The present findings suggest a small association between elective CS and IVD and T1D. The sibling-control results, however, suggest that these findings are not consistent with causal effects of mode of delivery on T1D and may be due to familial confounders such as genetic susceptibility and environmental factors.

Differences in the gut microbiota of healthy children and those with type 1 diabetes

BACKGROUND

Intestinal barriers, intestinal flora, and mucosal immunity are the main factors responsible for the development of various allergic and autoimmune diseases. The aim of this study was to investigate the relationship between the intestinal flora of children and the presence of type 1 diabetes, and to determine if gut microbiota could partly explain the etiology of the disease.

METHODS

Fecal flora analysis was done using quantitative cultures on selective and non-selective media with different thermal and atmospheric conditions for bacterial and fungal growth. The study group consisted of 35 patients (16 female, 19 male; mean age, 10.73 ± 4.16 years), who had been followed by the University of Istanbul, Cerrahpasa Medical Faculty, Department of Pediatrics, and were newly diagnosed with type 1 diabetes. The control group consisted of 35 healthy subjects (15 female, 20 male; mean age, 9.96 ± 4.09 years), who were randomly selected and had similar demographics.

RESULTS

Bifidobacterium colonization was lower in patients with type 1 diabetes compared to the control group, whereas Candida albicans and Enterobacteriaceae other than Echerichia coli colonization was increased.

CONCLUSION

A decrease in beneficial anaerobic bacteria levels and a concomitant increase in Enterobacteriaceae other than E. coli and C. albicans colonization may lead to a disturbance in the ecological balance of intestinal flora, which could be a triggering factor in type 1 diabetes etiology.

Early childhood infections and the risk of islet autoimmunity: the Diabetes Autoimmunity Study in the Young (DAISY)

OBJECTIVE

Type 1 diabetes is a common chronic childhood disease, and the incidence is increasing globally. Childhood infections are considered a potential environmental trigger of type 1 diabetes. Alternatively, improved hygiene and reduced childhood infections could explain the increase in type 1 diabetes in developed countries. The association of reported illnesses during infancy and later development of islet autoimmunity (IA) were examined in the Diabetes Autoimmunity Study in the Young.

RESEARCH DESIGN AND METHODS

Complete illness interviews through 9 months of age were collected for 1,729 children-1,174 without a family history of type 1 diabetes and 555 with a first-degree relative with type 1 diabetes. Persistent IA was defined as positive antibodies to insulin, glutamic acid decarboxylase, or tyrosine phosphatase on at least two consecutive study visits.

RESULTS

There were 109 children with persistent IA among the 1,729 children with illness records. A greater number of gastrointestinal illnesses were associated with an increased risk of IA, but only among children who were exposed to gluten-containing grains (wheat or barley) either <4 months of age (hazard ratio 1.37 [95% CI 1.22-1.55]; P < 0.0001) or ≥7 months of age (1.12 [1.05-1.19]; P = 0.0005) compared with 4-6 months of age (P for interaction = 0.02). There were no associations of upper respiratory symptoms, respiratory illnesses, or fevers with IA.

CONCLUSIONS

Specific pathogens such as enteroviruses or rotavirus may increase the risk of IA in the presence of existing inflammation induced by diet.

Current evidence on the associations of breastfeeding, infant formula, and cow's milk introduction with type 1 diabetes mellitus: a systematic review

Current evidence provides contradictory results in regards to the associations of breastfeeding or early introduction of cow's milk and formula with the development of type 1 diabetes (T1D). The aim of this systematic review was to evaluate the type of feeding, duration of breastfeeding, time of introduction of formula or cow's milk, and the potential impact on developing T1D. The literature search was conducted based on the standards outlined in the MOOSE Guidelines for Meta-Analyses and Systematic Reviews of Observational Studies and yielded a total of 161 studies, 28 of which were included in this review. Twenty seven of the included studies were case-control and one was a prospective cohort study. Eight of the studies indicated breastfeeding has a protective role against the development of T1D. Seven additional studies emphasized that a short period or absence of breastfeeding could be a risk factor for T1D development. The results of this systematic review indicate a short duration and/or a lack of breastfeeding may constitute a risk factor for the development of T1D later in life.

The pathogenesis and natural history of type 1 diabetes

The purpose of this article is to provide an overview that summarizes much in the way of our current state of knowledge regarding the pathogenesis and natural history of type 1 diabetes in humans. This information is presented to the reader as a series of seminal historical discoveries that, when advanced through research, transformed our understanding of the roles for the immune system, genes, and environment in the formation of this disease. In addition, where longitudinal investigations of these three facets occurred, their roles within the development of type 1 diabetes, from birth to symptomatic onset and beyond, are discussed, including their most controversial elements. Having an understanding of this disorder's pathogenesis and natural history is key for attempts seeking to understand the issues of what causes type 1 diabetes, as well as to develop a means to prevent and cure the disorder.

Cesarean section and interferon-induced helicase gene polymorphisms combine to increase childhood type 1 diabetes risk

OBJECTIVE

The incidence of type 1 diabetes is increasing. Delivery by cesarean section is also more prevalent, and it is suggested that cesarean section is associated with type 1 diabetes risk. We examine associations between cesarean delivery, islet autoimmunity and type 1 diabetes, and genes involved in type 1 diabetes susceptibility.

RESEARCH DESIGN AND METHODS

Cesarean section was examined as a risk factor in 1,650 children born to a parent with type 1 diabetes and followed from birth for the development of islet autoantibodies and type 1 diabetes.

RESULTS

Children delivered by cesarean section (n = 495) had more than twofold higher risk for type 1 diabetes than children born by vaginal delivery (hazard ratio [HR] 2.5; 95% CI 1.4-4.3; P = 0.001). Cesarean section did not increase the risk for islet autoantibodies (P = 0.6) but was associated with a faster progression to diabetes after the appearance of autoimmunity (P = 0.015). Cesarean section-associated risk was independent of potential confounder variables (adjusted HR 2.7;1.5-5.0; P = 0.001) and observed in children with and without high-risk HLA genotypes. Interestingly, cesarean section appeared to interact with immune response genes, including CD25 and in particular the interferon-induced helicase 1 gene, where increased risk for type 1 diabetes was only seen in children who were delivered by cesarean section and had type 1 diabetes-susceptible IFIH1 genotypes (12-year risk, 9.1 vs. <3% for all other combinations; P < 0.0001).

CONCLUSIONS

These findings suggest that type 1 diabetes risk modification by cesarean section may be linked to viral responses in the preclinical autoantibody-positive disease phase.

STATISTICAL EVALUATION OF FAMILIAL RISK FACTORS IN TYPE 1 DIABETES

In this paper the familial risk factors related to type 1 diabetes is studied. The analysis is based on data collected during epidemiological research performed from 1989–1996 in Upper Silesia, Poland. Different statistical models that allow for evaluating risk factors are discussed and applied to the data.

Early-pregnancy cytokines in mothers to children developing multiple, persistent islet autoantibodies, type 1 diabetes, or both before 7 years of age

PROBLEM

Increased levels of serum cytokines in early pregnancy may increase the risk of type 1 diabetes in the offspring.

METHOD OF STUDY

Early-pregnancy (between 10 and 16 gestational weeks) serum samples from non-diabetic index mothers (n = 48) of children who developed islet autoimmunity, type 1 diabetes, or both before 7 years of age were analyzed for IFN-γ, IL-10, IL-12, IL-13, IL-1β, IL-2, IL-4, IL-5, CXCL8, and TNF. Control mothers (n = 93) were matched for age, sampling date, and HLA-DQ genotypes.

RESULTS

IFN-γ (P = 0.02) and IL-1β (P = 0.04) were elevated in the index mothers. All cytokines except IL-4 were highly correlated (P < 0.0001). IFN-γ [OR 1.39 (1.04, 1.85), P = 0.026] and possibly IL-2 [OR 1.21 (0.99, 1.48), P = 0.057] in early pregnancy were associated with an increased risk of multiple, persistent islet autoantibodies, type 1 diabetes, or both before 7 years of age in the offspring. However, the statistical significance for IL-2 was lost in the logistic regression when adjusted for gestational length at delivery and parity.

CONCLUSION

Increased Th1 cytokine levels during early pregnancy might contribute to an increased risk of islet autoimmunity, type 1 diabetes, or both in the offspring.

Relationship of maternal weight status and weight gain rate during pregnancy to the development of advanced beta cell autoimmunity in the offspring: a prospective birth cohort study

OBJECTIVE

This study set out to examine how maternal initial body mass index (BMI) and weight gain during pregnancy associate with advanced beta cell autoimmunity in the offspring.

SUBJECTS

A population-based birth cohort of 4093 children with increased human leukocyte antigen (HLA)-conferred susceptibility to type 1 diabetes (T1D) and their mothers were recruited between 1997 and 2002 in two university hospital regions in Finland.

METHODS

The children were monitored for T1D-associated autoantibodies at 3- to 12-month intervals. Advanced beta cell autoimmunity was defined as repeated positivity for islet cell antibodies and at least one of the other three autoantibodies (antibodies to insulin, glutamate decarboxylase and islet antigen 2). Mothers were asked to record the results of the weight measurements during their first and last visits to the antenatal clinic. The initial BMI and weight gain rate were calculated for each woman.

RESULTS

Altogether, 175 children developed advanced beta cell autoimmunity or T1D during the follow-up. Maternal BMI before pregnancy or weight gain during pregnancy was not associated with the end-point. Maternal vocational education was associated with child's smaller risk of developing advanced beta cell autoimmunity.

Infant anthropometry, early life infection, and subsequent risk of type 1 diabetes mellitus: a prospective birth cohort study

BACKGROUND

Higher birthweight is associated with increased type 1 diabetes mellitus (T1DM) risk, but the contribution of higher adiposity or lean mass is unclear. In this Tasmanian infant cohort, early upper respiratory infection has been associated with higher asthma risk.

PATIENTS AND METHODS

Eligible infants represented one-fifth of live births in Tasmania, 1988-1995. Hospital interview data (day 6) were obtained on 96.3% (10 628/11 040), home (5 wk) visit data (38 d) on 92.9% (9876/10 628) of those, then a phone (12 wk) interview (87 d). Tricep and subscapular skinfold measures and upper arm circumference were recorded at the first two interviews. T1DM cases (n = 26) arising from the age of 16 or under in Tasmania from 1988 to 2006 were ascertained.

RESULTS

Higher birthweight [adjusted odds ratio (AOR) 2.82 (95% CI 1.31-6.09)], lean mid-upper arm circumference [AOR 1.76 (95% CI 1.16-2.66)], not skinfold measures, were associated with T1DM risk. Children with an early upper respiratory tract infection by 5-wk visit [AOR 2.74 (95% CI 1.19-6.32)] or ear infection by 12-wk interview [AOR 3.44 (95% CI 1.00-11.79)] were also at higher risk. Putative markers of altered microbial exposure such as resident density were not associated with T1DM risk but the effect of increasing birth order on T1DM risk differed for older (AOR 0.41, p = 0.02) than young mother (AOR 2.45, p = 0.01); difference in effect, p = 0.001.

CONCLUSION

In this cohort, early upper respiratory tract infection was associated with T1DM risk, as had been previously found for asthma, consistent with immunoinflammatory upregulation. Using the detailed anthropometric measures available, the link between higher birthweight and T1DM did not appear to reflect increased adiposity.

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.

Maternal and neonatal risk factors for childhood type 1 diabetes: a matched case-control study

Background

An interaction between genetic susceptibility and environmental factors is thought to be involved in the aetiology of type 1 diabetes. The aim of this study was to investigate maternal and neonatal risk factors for type 1 diabetes in children under 15 years old in Grampian, Scotland.

Methods

A matched case-control study was conducted by record linkage. Cases (n = 361) were children born in Aberdeen Maternity Hospital from 1972 to 2002, inclusive, who developed type 1 diabetes, identified from the Scottish Study Group for the Care of Diabetes in the Young Register. Controls (n = 1083) were randomly selected from the Aberdeen Maternity Neonatal Databank, matched by year of birth. Exposure data were obtained from the Aberdeen Maternity Neonatal Databank. Conditional logistic regression was used to evaluate the association between various maternal and neonatal factors and the risk of type 1 diabetes.

Results

There was no evidence of statistically significant associations between type 1 diabetes and maternal age, maternal body mass index, previous abortions, pre-eclampsia, amniocentesis, maternal deprivation, use of syntocinon, mode of delivery, antepartum haemorrhage, baby's sex, gestational age at birth, birth order, birth weight, jaundice, phototherapy, breast feeding, admission to neonatal unit and Apgar score (P > 0.05). A significantly decreased risk of type 1 diabetes was observed in children whose mothers smoked at the booking appointment compared to those whose mothers did not, with an adjusted OR of 0.67, 95% CI (0.46, 0.99).

Conclusions

This case-control study found limited evidence of a reduced risk of the development of type 1 diabetes in children whose mothers smoked, compared to children whose mothers did not. No evidence was found of a significant association between other maternal and neonatal factors and childhood 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.

Birthweight and the risk of childhood-onset type 1 diabetes: a meta-analysis of observational studies using individual patient data

AIMS/HYPOTHESIS

We investigated whether children who are heavier at birth have an increased risk of type 1 diabetes.

METHODS

Relevant studies published before February 2009 were identified from literature searches using MEDLINE, Web of Science and EMBASE. Authors of all studies containing relevant data were contacted and asked to provide individual patient data or conduct pre-specified analyses. Risk estimates of type 1 diabetes by category of birthweight were calculated for each study, before and after adjustment for potential confounders.Meta-analysis techniques were then used to derive combined ORs and investigate heterogeneity between studies.

RESULTS

Data were available for 29 predominantly European studies (five cohort, 24 case-control studies), including 12,807 cases of type 1 diabetes. Overall, studies consistently demonstrated that children with birthweight from 3.5 to 4 kg had an increased risk of diabetes of 6% (OR 1.06 [95% CI 1.01-1.11]; p=0.02) and children with birthweight over 4 kg had an increased risk of 10% (OR 1.10 [95% CI 1.04-1.19]; p=0.003), compared with children weighing 3.0 to 3.5 kg at birth. This corresponded to a linear increase in diabetes risk of 3% per 500 g increase in birthweight (OR 1.03 [95% CI 1.00-1.06]; p=0.03). Adjustments for potential confounders such as gestational age, maternal age, birth order, Caesarean section, breastfeeding and maternal diabetes had little effect on these findings.

CONCLUSIONS/INTERPRETATION

Children who are heavier at birth have a significant and consistent, but relatively small increase in risk of type 1 diabetes.

Maternal age at birth and childhood type 1 diabetes: a pooled analysis of 30 observational studies

OBJECTIVE

The aim if the study was to investigate whether children born to older mothers have an increased risk of type 1 diabetes by performing a pooled analysis of previous studies using individual patient data to adjust for recognized confounders.

RESEARCH DESIGN AND METHODS

Relevant studies published before June 2009 were identified from MEDLINE, Web of Science, and EMBASE. Authors of studies were contacted and asked to provide individual patient data or conduct prespecified analyses. Risk estimates of type 1 diabetes by maternal age were calculated for each study, before and after adjustment for potential confounders. Meta-analysis techniques were used to derive combined odds ratios and to investigate heterogeneity among studies.

RESULTS

Data were available for 5 cohort and 25 case-control studies, including 14,724 cases of type 1 diabetes. Overall, there was, on average, a 5% (95% CI 2-9) increase in childhood type 1 diabetes odds per 5-year increase in maternal age (P = 0.006), but there was heterogeneity among studies (heterogeneity I(2) = 70%). In studies with a low risk of bias, there was a more marked increase in diabetes odds of 10% per 5-year increase in maternal age. Adjustments for potential confounders little altered these estimates.

CONCLUSIONS

There was evidence of a weak but significant linear increase in the risk of childhood type 1 diabetes across the range of maternal ages, but the magnitude of association varied between studies. A very small percentage of the increase in the incidence of childhood type 1 diabetes in recent years could be explained by increases in maternal age.

Birth weight, early weight gain, and subsequent risk of type 1 diabetes: systematic review and meta-analysis

Previous studies suggest that birth weight and weight gain during the first year of life are related to later risk of type 1 diabetes. The authors performed a systematic review and meta-analysis on these associations. Twelve studies involving 2,398,150 persons of whom 7,491 had type 1 diabetes provided odds ratios and 95% confidence intervals of type 1 diabetes associated with birth weight. Four studies provided data on weight and/or weight gain during the first year of life. High birth weight (>4,000 g) was associated with increased risk of type 1 diabetes (odds ratio = 1.17, 95% confidence interval (CI): 1.09, 1.26). According to sensitivity analysis, this result was not influenced by particular study characteristics. The pooled confounder-adjusted estimate was 1.43 (95% CI: 1.11, 1.85). No heterogeneity was found (I(2) = 0%) and no publication bias. Low birth weight (<2,500 g) was associated with a nonsignificantly decreased risk of type 1 diabetes (odds ratio = 0.82, 95% CI: 0.54, 1.23). Each 1,000-g increase in birth weight was associated with a 7% increase in type 1 diabetes risk. In all studies, patients with type 1 diabetes showed increased weight gain during the first year of life, compared with controls. This meta-analysis indicates that high birth weight and increased early weight gain are risk factors for type 1 diabetes.

Childhood body mass index (BMI), breastfeeding and risk of Type 1 diabetes: findings from a longitudinal national birth cohort

AIMS

To perform a longitudinal analysis of the association between childhood body mass index (BMI) and later risk of Type 1 diabetes, controlling for socio-economic status, birthweight, height in early and late childhood, breastfeeding history and pubertal status.

METHODS

Analysis of the 1970 British Birth Cohort, followed up at age 5, 10 and 30 years (n = 11,261). Data were available on birthweight, breastfeeding; height, weight, pubertal status, socio-economic status at age 10 years; self-report data on history of diabetes (type, age at onset) at age 30 years. Cox proportional hazards models were used to examine relations of childhood growth, socio-economic status and breastfeeding history to the incidence of Type 1 diabetes between 10 and 30 years of age.

RESULTS

Sixty-one subjects (0.5%) reported Type 1 diabetes at 30 years of age; 47 (77%) reported onset >or= age 10 years. Higher BMI z-score at 10 years predicted higher risk of subsequent Type 1 diabetes (hazard ratio 1.8, 95% confidence interval 1.2 to 2.8, P = 0.01) when adjusted for birthweight, pubertal status, breastfeeding history and socio-economic status. Repeating the model for childhood obesity, the hazard ratio was 3.1 (1.0, 9.3; P = 0.05). Birthweight, breastfeeding, height growth and pubertal timing were not associated with incidence of Type 1 diabetes.

CONCLUSIONS

Higher BMI in childhood independently increased the risk of later Type 1 diabetes, supporting suggestions that obesity may provide a link between Type 1 and Type 2 diabetes. This supports observations of a rise in Type 1 diabetes prevalence. Reduction in childhood obesity may reduce the incidence of Type 1 as well as Type 2 diabetes.

Prevalence of allergic symptoms among children with diabetes mellitus type 1 of different socioeconomic status

The aim of the study was to assess the possible associations between allergies and type 1 diabetes mellitus (DM1), stratified by social class. We studied 127 children with DM1 with a median age of 10.8 yr and 150 controls of comparable age and sex distribution. The parents completed questionnaires on their education and occupation and on their children's history of allergic symptoms, breast-feeding, viral infections, and measles-mumps-rubella (MMR) vaccination. Lower family's social class was more frequently encountered among the DM1 families than in the controls (OR = 0.56, 95% CI: 0.35-0.92). The occurrence of any allergic symptoms among children with DM1 (35.45%) was not significantly different from the controls (38.78%), neither in the total group (OR = 0.87, 95% CI: 0.52-1.45) nor in the stratified analysis by social class. Similar findings were observed regarding the different types of allergic symptoms. In the univariate analysis, breast-feeding, the experience of viral infections, and MMR vaccination were found to be protective of DM1 presentation in both upper and lower social classes. In the multiple logistic regression analysis, the experience of more than 2 infections/yr (OR = 0.12, 95% CI: 0.04-0.34), the origin from middle and upper social classes (OR = 0.42, 95% CI: 0.22-0.80) and breast-feeding (OR = 0.58, 95% CI: 0.31-1.07) were protective of DM1 occurrence. In children with DM1, the presence of allergic symptoms was not associated with the development of DM1. Among the environmental factors, the origin from middle or upper social classes, breast-feeding, the experience of viral infections, and MMR vaccination were found to have a protective effect on DM1 presentation.

Atopy, home environment and the risk of childhood-onset type 1 diabetes: a population-based case-control study

BACKGROUND

The marked increases in the incidence of type 1 diabetes in recent decades strongly suggest the role of environmental influences. These environmental influences remain largely unknown.

OBJECTIVE

To investigate atopy and home environment (such as children living at home, sharing a bedroom and house moves) as potential risk factors for type 1 diabetes.

SUBJECTS AND METHOD

In Northern Ireland, 175 children with type 1 diabetes and 4859 control children completed a questionnaire on atopy experience, family composition and home environment. Control children from two age groups (6-8 yr old and 13-14 yr old) were identified from randomly selected primary and secondary schools across Northern Ireland. Cases were identified from a population-based type 1 diabetes register.

RESULTS

There was little evidence of a difference in the proportion of participants with a history of atopy in the cases compared with controls. There was a significant reduction in the risk of diabetes in children who lived with more siblings {odds ratio (OR) = 0.58 [95% confidence interval (95% CI) 0.39-0.85] in children who lived with three or more siblings compared with one or none} and in children who moved house more often [OR = 0.59 (95% CI 0.40-0.88) in children who moved house twice or more compared with never].

CONCLUSION

The reduced risk of type 1 diabetes in children living with siblings, sharing a bedroom and moving house more often could reflect the protection afforded by exposure to infections in early life and consequently may provide support for the hygiene hypothesis.

Caesarean section is associated with an increased risk of childhood-onset type 1 diabetes mellitus: a meta-analysis of observational studies

AIMS/HYPOTHESIS

The aim of this study was to investigate the evidence of an increased risk of childhood-onset type 1 diabetes in children born by Caesarean section by systematically reviewing the published literature and performing a meta-analysis with adjustment for recognised confounders.

METHODS

After MEDLINE, Web of Science and EMBASE searches, crude ORs and 95% CIs for type 1 diabetes in children born by Caesarean section were calculated from the data reported in each study. Authors were contacted to facilitate adjustments for potential confounders, either by supplying raw data or calculating adjusted estimates. Meta-analysis techniques were then used to derive combined ORs and to investigate heterogeneity between studies.

RESULTS

Twenty studies were identified. Overall, there was a significant increase in the risk of type 1 diabetes in children born by Caesarean section (OR 1.23, 95% CI 1.15-1.32, p < 0.001). There was little evidence of heterogeneity between studies (p = 0.54). Seventeen authors provided raw data or adjusted estimates to facilitate adjustments for potential confounders. In these studies, there was evidence of an increase in diabetes risk with greater birthweight, shorter gestation and greater maternal age. The increased risk of type 1 diabetes after Caesarean section was little altered after adjustment for gestational age, birth weight, maternal age, birth order, breast-feeding and maternal diabetes (adjusted OR 1.19, 95% CI 1.04-1.36, p = 0.01).

CONCLUSIONS/INTERPRETATION

This analysis demonstrates a 20% increase in the risk of childhood-onset type 1 diabetes after Caesarean section delivery that cannot be explained by known confounders.

Early infant feeding and risk of type 1 diabetes mellitus-a nationwide population-based case-control study in pre-school children

BACKGROUND

The evidence on the role of environmental factors in the development of type 1 diabetes is conflicting. Reducing potential bias and the variety of exposures, we investigated the association between type 1 diabetes risk and nutritional and environmental exposures in pre-school children.

METHODS

This nationwide population-based case-control study included 760 cases under 5 years of age newly diagnosed with type 1 diabetes during 1992-1995. From the general population, 1,871 controls were randomly selected and individually matched on age ( +/- 1 year), sex, and residence. Information on infant diet, foetal, perinatal and socio-economic factors, and familial diabetes was obtained by a parent-administered questionnaire. Data were analysed by multiple conditional logistic regression.

RESULTS

Duration of breastfeeding and age at introduction of bottle-feeding were inversely associated with type 1 diabetes risk according to a dose-response relationship (trend test p < 0.05). Adjusted odd ratios (95% CI) for a long breastfeeding period and a late introduction of bottle-feeding (>or=5 month versus < 2 weeks) were 0.71 (0.54-0.93) and 0.80 (0.62-1.04), respectively. Familial type 1 diabetes, maternal age > 40 years, and low birth weight were found more frequently among diabetic than among control children. Current cow's milk consumption, higher social status, and a larger family were associated with a reduced diabetes risk. Up to one half of the diabetic cases in the population could be attributed to modifiable exposures.

CONCLUSIONS

Our findings indicate that infant feeding is associated with type 1 diabetes risk and that a considerable part of new type 1 diabetic cases is potentially preventable.

No association between routinely recorded infections in early life and subsequent risk of childhood-onset Type 1 diabetes: a matched case-control study using the UK General Practice Research Database

AIMS

To determine whether children with infections in early life (recorded routinely in general practice) have a reduced risk of Type 1 diabetes, as would be expected from the hygiene hypothesis.

METHODS

Children with Type 1 diabetes and up to 20 matched (on year of birth, sex and region) control subjects were selected from a cohort of children born in the UK at General Practice Research Database practices. For each child, the frequency of general practitioner consultations for infections and prescriptions for antibiotics in the first year of life were determined. Odds ratios (ORs) and 95% confidence intervals (95%CIs) were calculated using conditional logistic regression.

RESULTS

The main analysis included 367 case and 4579 matched control subjects. There was no evidence of any reduction in the subsequent risk of Type 1 diabetes in children with at least one infection in the first year of life (OR = 1.03, 95%CI 0.79, 1.34) or in children prescribed antibiotics in the first year of life (OR = 1.03, 95%CI 0.82, 1.29). Further analyses also revealed little evidence of a difference in subsequent risk of Type 1 diabetes after different types of infection in the first year of life (including gastrointestinal, conjunctivitis, otitis media and upper and lower respiratory tract). Analyses of infections in the first 2 years of life reached similar conclusions.

CONCLUSIONS

This study provides no evidence of an association between infections in early life and subsequent risk of childhood-onset Type 1 diabetes and therefore does not support the hygiene hypothesis.

Worldwide childhood type 1 diabetes incidence--what can we learn from epidemiology?

Type 1 diabetes is the most common form of diabetes in most part of the world, although reliable data are still unavailable in several countries. Wide variations exist between the incidence rates of different populations, incidence is lowest in China and Venezuela (0.1 per 100,000 per year) and highest in Finland and Sardinia (37 per 100,000 per year). In most populations girls and boys are equally affected. In general, the incidence increases with age, the incidence peak is at puberty. After the pubertal years, the incidence rate significantly drops in young women, but remains relatively high in young adult males up to the age 29-35 years. Prospective national and large international registries (DIAMOND and EURODIAB) demonstrated an increasing trend in incidence in most regions of the world over the last few decades and increases seem to be the highest in the youngest age group. Analytical epidemiological studies have identified environmental risk factors operating early in life which might have contributed to the increasing trend in incidence. These include enteroviral infections in pregnant women, older maternal age (39-42 years), preeclampsia, cesarean section delivery, increased birthweight, early introduction of cow's milk proteins and an increased rate of postnatal growth (weight and height). Optimal vitamin D supplementation during early life has been shown to be protective. Some of these environmental risk factors such as viruses may initiate autoimmunity toward the beta cell, other exposures may put on overload on the already affected beta cell and thus accelerate the disease process.

Perinatal factors associated with subsequent diabetes mellitus in the child: record linkage study

AIMS

To report on associations between perinatal factors and the subsequent development of diabetes mellitus under the age of 30 years in the offspring.

METHODS

Analysis of linked hospital statistical records, comparing perinatal factors relating to the birth of 518 people admitted to hospital for diabetes with the same factors in 292 845 others, in a defined population in southern England from 1963 to 1999.

RESULTS

Diabetes mellitus was much more common in children of mothers with diabetes than in others (odds ratio 6.42; 95% confidence interval 4.18-9.86). There was no significant association with birthweight or gestational age separately. Diabetes was more common in those in the highest quintile of 'birthweight for gestational age' compared with the lowest four quintiles combined (odds ratio 1.33; 95% confidence interval 1.08-1.64), but there was no consistent gradient of increasing frequency of diabetes across the lowest four quintiles. There were no significant associations between diabetes and mothers' age, parity, social class, or smoking during pregnancy, or between babies' mode of delivery or any other perinatal factors investigated. All results were similar when the analysis was confined to diabetes in people aged < 15 years.

CONCLUSIONS

We found a strong association between diabetes in the child-mainly, if not entirely Type 1 diabetes-and maternal diabetes. Diabetes was slightly more common in the heaviest quintile of birthweight for gestational age than in other quintiles. There were no significant associations between diabetes and the other perinatal factors studied.

Socioeconomic conditions and type 1 diabetes in childhood in North Rhine-Westphalia, Germany

AIMS/HYPOTHESIS

The aim of the study was to investigate the relationships between childhood type 1 diabetes and socioeconomic conditions, which might provide clues to the aetiology of the disease.

MATERIALS AND METHODS

In an ecological study, we investigated the relationships between socioeconomic conditions and the incidence of type 1 diabetes incidence among children aged 0-14 years in North Rhine-Westphalia (NRW), Germany, between 1996 and 2000 at the level of the 33 districts. Incidence data were obtained from the population-based NRW diabetes register and regional socioeconomic data from official statistics. Associations were assessed by Poisson regression models and Bayesian conditionally autoregressive regression models (CAR).

RESULTS

In simple Poisson regression, population density, proportion of non-German nationals in the population, measures of income, education and professional training, and deprivation scores were significantly associated with diabetes risk (p < 0.01). An increase of about one interquartile range (IQR) in population density, proportion of non-German nationals or household income was associated with a 9-12% decrease in diabetes incidence. A rise of about one IQR in income ratio, measures of education and professional training, or in deprivation score (high values correspond to high deprivation) was associated with an 8-12% incidence increase. There was a significantly 'linear' increasing incidence trend across five deprivation classes (relative risk: 1.06; 95% CI: 1.03-1.09). All associations were confirmed when overdispersion and spatial autocorrelation were accounted for in Poisson and CAR models.

CONCLUSIONS/INTERPRETATIONS

The results raise the possibility that the risk for type 1 diabetes is higher for children living in socially deprived and less densely populated areas. Subsequent investigations are necessary to verify the observed ecological relations at the individual level and to identify the causal factors behind the socioeconomic indicators.

Secular trends, disease maps and ecological analyses of the incidence of childhood onset Type 1 diabetes in Northern Ireland, 1989-2003

AIMS

To investigate secular trends in the incidence of Type 1 diabetes in Northern Ireland over the period 1989-2003. To highlight geographical variations in the incidence of Type 1 diabetes by producing disease maps and to compare incidence rates by relevant area characteristics.

METHODS

New cases of Type 1 diabetes in children aged 0-14 years in Northern Ireland were prospectively registered from 1989 to 2003. Standardized incidence rates were calculated and secular trends investigated. Bayesian methodology was used to produce maps of disease incidence using small geographical areas (582 electoral wards). Ecological analyses were conducted using Poisson regression to investigate incidence rates by area characteristics at a finer geographical subdivision (5022 census output areas).

RESULTS

In Northern Ireland during 1989-2003, there were 1433 new cases, giving a directly standardized incidence rate of 24.7 per 100,000 person-years. This incidence rate increased by a mean of 4.2% per annum. Disease maps highlighted higher incidence rates in the predominately rural north-east of the province and lower incidence rates in the urban areas around Belfast in the east and Derry in the north-west of the province. Ecological analysis identified higher incidence in rural areas (P < 0.001), areas with low migration rates (P = 0.002), affluent areas (P < 0.0001), sparsely populated areas (P = 0.0001) and remote areas (P = 0.005). CONCLUSIONS In Northern Ireland the incidence of Type 1 diabetes is increasing. The observed higher incidence in rural, affluent, sparsely populated and remote areas may reflect a reduced or delayed exposure to infections in these areas.

Environmental factors in the development of Type 1 diabetes

Environmental factors appear to play an important role in the pathogenesis of childhood-onset type 1 diabetes (T1D). The most important factors are thought to be infectious, dietary, perinatal, and psychosocial. Enteroviruses (especially Coxsackie B virus), breastfeeding, the early presence or lack of certain foods, birth weight, childhood over-nutrition, maternal islet autoimmunity, and negative stress events have been shown to be related to the prevalence of T1D. However, clear conclusions to date are limited because most studies lacked power to detect exposure/disease associations, were not prospective or long-term, did not start in infancy, had imprecise or infrequent exposure estimates, had confounding exposures, and failed to account for genetic susceptibility. In addition to the identification of specific antigenic triggers, several more general hypotheses, including the accelerator and hygiene hypotheses, are testable approaches worth pursuing.

Absence of breast-feeding is associated with the risk of type 1 diabetes: a case-control study in a population with rapidly increasing incidence

There are indications that the effect of environmental factors on the risk of type 1 diabetes mellitus (T1DM) is increasing over time. This can be documented by the rapid increase of T1DM incidence in genetically stable populations. Our aim was to study an association of T1DM with the variable factors of the perinatal period and of early infancy, using data from children born over a period of changing exposure to some of the studied factors. A case-control dataset was analysed, consisting of 868 diabetic children and 1,466 anonymous controls, mostly schoolmates of the children with T1DM. The data were collected using structured questionnaires completed by parents. After performing univariate analyses, the associations were analysed using multiple logistic regression adjusted for potential confounders, including the year of birth. The risk of T1DM decreased with increasing duration of breast-feeding, while no breast-feeding was associated with an increased T1DM risk, OR=1.93 [95% CI: 1.33-2.80], breast-feeding for more than 12 months was protective, OR=0.42 [95% CI: 0.22-0.81], both being relative to the reference category of breast-feeding for 1-3 months. A short duration of day-care attendance (none or less than 1 year) was weakly associated with the risk of T1DM, OR=1.65 [95% CI: 1.05-2.62]. No association was detected between T1DM and signs of prenatal infections, perinatal stress factors, birth size and weight, indicators of crowding or the presence of a domestic pet in the household. Short breast-feeding period and short attendance to day care is associated with the risk of T1DM in Czech children.

Type 1 diabetes mellitus: etiology, presentation, and management

This article reviews our current understanding of the etiology, presentation, and management of type 1 diabetes. The discussion includes a review of the natural history of diabetes, the complex relationship between genetic and environmental risk for type 1 diabetes, and current methods for prediction of type 1 diabetes. The article also reviews the current management of children who have new-onset type 1 diabetes, age-appropriate management goals, and diabetes complications. Finally, the article discusses the future of diabetes screening programs and the progress toward the ultimate goal of curing type 1 diabetes.

No evidence for association of the TATA-box binding protein glutamine repeat sequence or the flanking chromosome 6q27 region with type 1 diabetes

Susceptibility to the autoimmune disease type 1 diabetes has been linked to human chromosome 6q27 and, moreover, recently associated with one of the genes in the region, TATA box-binding protein (TBP). Using a much larger sample of T1D families than those studied by others, and by extensive re-sequencing of nine other genes in the proximity, in which we identified 279 polymorphisms, 83 of which were genotyped in up to 725 T1D multiplex and simplex families, we obtained no evidence for association of the TBP CAG/CAA (glutamine) microsatellite repeat sequence with disease, or for nine other genes, PDCD2, PSMB1, KIAA1838, DLL1, dJ894D12.4, FLJ25454, FLJ13162, FLJ11152, PHF10 and CCR6. This study also provides an exon-based tag single nucleotide polymorphism map for these 10 genes that can be used for analysis of other diseases.

Early childhood risk factors associated with type 1 diabetes – is gender important?

BACKGROUND

The incidence of childhood diabetes is increasing in Denmark as in the rest of the world. The aim of this investigation was to study intrauterine and early childhood risk factors for insulin dependent diabetes mellitus, and to evaluate gender differences in the effect of these. METHODS/MATERIAL: A number of 602 diabetic cases aged 0-14 years diagnosed 1996-1999 were identified from the Danish register of childhood diabetes. A total of 1490 non-diabetic healthy children matched by gender and date of birth were randomly selected from the Danish population register. In addition a combination of national register data and questionnaire data was used.

RESULTS

High parental age, neonatal infections and pre-eclampsia were associated with type 1 diabetes in boys, whereas being preterm was associated with an increased risk in girls. An increased risk was associated with a family history of diabetes and amniocentesis, while a decreased risk was associated with increasing birth order and maternal smoking. In a multiple logistic regression analysis, the following risk factors were significantly associated with case-control status: maternal smoking (OR: 0.6(0.4-0.9)), neonatal infection in boys (OR: 5.5(1.4-21.8)), neonatal infection in girls (OR: 0.6(0.1-3.0)), amniocentesis (OR: 1.6(1.0-2.6)), preschool siblings (OR: 0.8(0.6-1.0)), introduction of cow's milk after the age of 3 months (OR: 0.7(0.4-0.9)) and a 1st degree family member with diabetes (OR: 9.1(95% CI:5.2-16)).

CONCLUSION

The study showed associations between several risk factors and childhood diabetes, for some risk factors the odds ratio in boys were different from the odds ratio in girls.

A new model for understanding the role of environmental factors in the origins of chronic illness: a case study of type 1 diabetes mellitus

There is a need for a new pathophysiological model explaining and linking the role of numerous non-genetic factors believed to contribute to origins of many chronic physical diseases. This article presents a theoretical model for explaining the confusing and often contradictory findings regarding the role of environmental influences in type 1 diabetes, a disease that has been widely studied, for which clear diagnostic criteria exist, and for which development of effective prevention strategies represents significant challenges. The model is formulated from the large database of research regarding increasing understanding of the interaction between environmental factors, physiology, and autonomic regulatory function. Data is integrated from research in the fields of the experience-dependent maturation of the nervous system and the neurophysiology of traumatic stress to demonstrate how disruptions in early bonding and attachment, including adverse events such as traumatic stress, are capable of causing: (1) long-term imbalances in autonomic regulatory function and (2) relative dominance of sympathetic or parasympathetic activity. The proposed model of autonomic dysfunction suggests that ongoing mechanisms promoting high glucose in the context of decreasing insulin production in type 1 diabetes represent a state of relative sympathetic dominance influenced by environmental factors affecting autonomic, immune and endocrine systems during critical period programming. The model further identifies a link between the many seemingly unrelated non-genetic risk factors, and appears capable of explaining contradictions and enigmas in epidemiological and clinical studies regarding non-genetic origins of type 1 diabetes, including the role of stress, variation in age of onset, and duration of the preclinical phase.

Parental age at delivery, birth order, birth weight and gestational age are associated with the risk of childhood Type 1 diabetes: a UK regional retrospective cohort study

AIMS

To investigate perinatal risk factors for childhood Type 1 diabetes in a UK population cohort.

METHODS

Perinatal data have been routinely recorded in Northern Ireland for all births in the period 1971-86 (n = 447 663). Diabetes status at the age of 15 years was ascertained in this cohort by identifying 991 children from 1079 registered with Type 1 diabetes diagnosed from 1971 to 2001 and date of birth in the period 1971-86.

RESULTS

Increased Type 1 diabetes risk was associated with higher maternal age, paternal age, birth weight and birth weight for gestational and lower gestational age. After adjustment for maternal age, the association between Type 1 diabetes and paternal age remained significant [relative risk (RR) = 1.52 (1.10, 2.09) comparing father's age 35 years or more to less than 25 years] but not vice versa [RR = 1.11 (0.80, 1.54) comparing mother's age 35 years or more to less than 25 years]. Increased birth order was associated with a significant decrease in the risk of Type 1 diabetes [adjusted RR = 0.75 (0.62, 0.90) comparing birth order three or more with firstborn], but this only became apparent when adjustment was made for maternal age. Furthermore this association with birth order was significant only for diabetes diagnosed under the age of 5 years.

CONCLUSIONS

Our analysis demonstrates, for the first time in a UK regional cohort setting, that maternal age and paternal age at delivery, birth order, birth weight and gestational age are significantly associated with Type 1 diabetes risk.

Secondary attack rate of type 1 diabetes in Colorado families

OBJECTIVE

Families of children diagnosed with type 1 diabetes require counseling concerning type 1 diabetes risk in nondiabetic siblings and parents. No U.S. population-specific life-table risk estimates are currently available for parents, and those for siblings (2-6% by age 20 years) are based on family studies completed before 1987.

RESEARCH DESIGN AND METHODS

We analyzed family histories of 1,586 patients in Colorado with type 1 diabetes (83% non-Hispanic white, 10% Hispanic, and 7% other) diagnosed before 16 years of age and interviewed during 1999-2002. Families of probands with type 2, undetermined, or secondary diabetes (n = 53) or those with incomplete data (n = 137) were excluded. The median age at onset of the proband was 7.1 years and the median diabetes duration 3.5 years. Cumulative risk estimates were calculated using survival analysis for 2,081 full siblings and 3,016 biological parents.

RESULTS

In siblings, the overall risk of type 1 diabetes by age 20 years was 4.4%, but it was significantly (P < 0.0001) higher in siblings of probands diagnosed under age 7 years than in those diagnosed later. In parents, the overall risk by age 40 years was 2.6% and higher in fathers (3.6%) than in mothers (1.7%) of probands (P < 0.001). Similar to siblings, the risk was also higher (P = 0.006) in parents of probands diagnosed <7 years of age than in those diagnosed later.

CONCLUSIONS

Current risks of type 1 diabetes in Colorado siblings and parents of type 1 diabetic probands are higher than in the 1982 Pittsburgh study but similar to contemporary European rates. Recurrence risk of type 1 diabetes is significantly higher in first-degree relatives of probands diagnosed at a young age.

Lack of association of the Ala(45)Thr polymorphism and other common variants of the NeuroD gene with type 1 diabetes

Variation in genes necessary for normal functioning and development of beta-cells, e.g., NEUROD1, which encodes a transcription factor for the insulin gene and is important in beta-cell development, causes maturity-onset diabetes of the young. Some studies have reported an association between a nonsynonymous Ala(45)Thr (+182G-->A) single nucleotide polymorphism (SNP) in NEUROD1 and type 1 diabetes, but this result has not been consistently found. To clarify this, we genotyped Ala(45)Thr in 2,434 type 1 diabetic families of European descent and Caucasian ethnicity from five different countries. Taking the allele frequency of 36% for Thr(45) and an odds ratio (OR) of 1.2, this sample provided >99% power to detect an association (P < 0.05). We could not confirm the association (P = 0.77). No evidence of population heterogeneity in the lack of association of Thr(45) with type 1 diabetes was observed. To evaluate the possibility that another NEUROD1 variant was associated with type 1 diabetes, we resequenced the gene in 32 U.K. affected individuals and identified and genotyped all common SNPs (minor allele frequency >10%; n = 5) in 786 families. We report no evidence of association of these common variants in NEUROD1 and type 1 diabetes in these samples.