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

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.

Tobacco exposure and diabetes-related autoantibodies in children: results from the ABIS study

Passive smoking has decreased in recent years ("increased hygiene"). Less environmental tobacco smoke (ETS) gives increased hygiene that, if the hygiene hypothesis is true, in turn might give more autoimmune diseases. The presence of auto antibodies is considered to be an early indicator of type 1 diabetes (T1D). Because tobacco exposure may influence the immune system, we analyzed the relation between passive smoking and development of autoantibodies. A subsample (n= 8794) of the children in the ABIS study was used for this analysis. The parents answered questionnaires on smoking from pregnancy and onwards, and blood samples from the children aged 2.5-3 years were analyzed for GADA and IA-2A. Results showed that there was no significant difference in the prevalence of GADA or IA-2A (>95 percentile) between tobacco-exposed and nonexposed children. It was concluded that passive smoking does not seem to influence development of diabetes-related autoantibodies early in life.

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.

Steep increase of incidence of childhood diabetes since 1999 in Austria. Time trend analysis 1979-2005. A nationwide study

In a prospective population-based incidence study all newly diagnosed type 1 diabetic patients 0-<15 years of age were registered by the Austrian Diabetes Incidence Study Group. The nationwide incidence of type 1 diabetes between 2000-2005 was compared with the previously published incidence rates. Long-term trends as well as seasonal trends were estimated by Poisson regression models. A total of 3,599 incident cases (1,908 boys; 1,691 girls) were identified. Case ascertainment was >92%. The overall incidence rate doubled from 7.3 (95% CI; 6.8-7.9)/100,000 in the period 1979-84 to 14.6 (95% CI, 13.7-15.4)/100,000 in the time period 2000-2005. A significant increase during the observation period of 26 years could be demonstrated in all age groups and both sexes (p<0.01), with the steepest increment during the last 5 years. Until 1994 the incidence rate in children 0-<5 years was rather stable, but afterwards increased dramatically with 9.2% (95% CI, 5.2-13.4) annually. Despite this steep increase in time trend, we did not observe a seasonal variation in this age group (0-<5) in contrast to significant seasonal variations in the groups 5-<10 and 10-<15 years of age. Over the past 26 years incidence of type 1 diabetes in childhood increased clearly in Austria. The steepest rise was observed in the last 5 years and in the younger age groups.

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.

Growth in the first year of life and the risk of type 1 diabetes in a Danish population

The aim of the study was to investigate whether growth parameters at birth and age 1 year were associated with type 1 diabetes (T1D) in the Danish population and to what extent this explains the increase in T1D incidence. The study is a population-based case-control study; it compares 490 cases from the Danish diabetes register 1996-99 aged 0-14 years and 696 randomly selected controls (2 per case) from the population register matched for gender and date of birth. We found an increased risk of T1D during childhood in children with a body mass index (BMI) on or above two standard deviations at age 1 year (OR = 3.77 [95% CI 1.41, 10.1]). Children developing diabetes were significantly taller at age 1 year (OR = 1.04 [95% CI 1.00, 1.08]). Children born 1981-99 have significantly higher BMI and weight at birth and a significantly lower BMI and weight at age 1 year compared with children born 1966-74. Thus the increasing incidence of T1D could not be explained by changes in growth parameters at birth or at age 1 year.

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.