Jannet Svensson

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

Aims/hypothesisThe 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.MethodsAfter 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.ResultsTwenty 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/interpretationThis 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.

Trends in childhood type 1 diabetes incidence in Europe during 1989–2008: evidence of non-uniformity over time in rates of increase

Aims/hypothesisThe aim of the study was to describe 20-year incidence trends for childhood type 1 diabetes in 23 EURODIAB centres and compare rates of increase in the first (1989–1998) and second (1999–2008) halves of the period.MethodsAll registers operate in geographically defined regions and are based on a clinical diagnosis. Completeness of registration is assessed by capture–recapture methodology. Twenty-three centres in 19 countries registered 49,969 new cases of type 1 diabetes in individuals diagnosed before their 15th birthday during the period studied.ResultsAscertainment exceeded 90% in most registers. During the 20-year period, all but one register showed statistically significant changes in incidence, with rates universally increasing. When estimated separately for the first and second halves of the period, the median rates of increase were similar: 3.4% per annum and 3.3% per annum, respectively. However, rates of increase differed significantly between the first half and the second half for nine of the 21 registers with adequate coverage of both periods; five registers showed significantly higher rates of increase in the first half, and four significantly higher rates in the second half.Conclusions/interpretationThe incidence rate of childhood type 1 diabetes continues to rise across Europe by an average of approximately 3–4% per annum, but the increase is not necessarily uniform, showing periods of less rapid and more rapid increase in incidence in some registers. This pattern of change suggests that important risk exposures differ over time in different European countries. Further time trend analysis and comparison of the patterns in defined regions is warranted.

Early mortality in EURODIAB population-based cohorts of type 1 diabetes diagnosed in childhood since 1989

Aims/hypothesisThe aims of this study were to provide a contemporary picture of mortality and causes of death in Europe following a diagnosis of type 1 diabetes made before the 15th birthday, and to examine excess mortality by country for possible links to incidence level or national prosperity.MethodsThirteen population-based EURODIAB registers in 12 countries followed-up 28,887 children diagnosed since 1989, either by record linkage to population registers or through contact with doctors providing care.ResultsThere were 141 deaths in the cohort during 219,061 person-years of follow-up compared with 69.1 deaths expected from national mortality rates, a standardised mortality ratio (SMR) of 2.0 (95% CI 1.7–2.4). The SMR varied from 0 to 4.7 between countries, but showed little relationship with the country’s incidence rate or gross domestic product (US

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

per capita). The SMR did not change significantly with attained age, calendar period or time since diagnosis. The female SMR (2.7; 95% CI 2.0–3.5) was greater than the male SMR (1.8; 95% CI 1.4–2.2), although absolute numbers of excess deaths were similar in the two sexes. One-third of deaths were classified as directly attributable to diabetes (many with mention of ketoacidosis) and half were unrelated to diabetes. There was a non-significant excess of accidental/violent deaths (48 observed vs 40.7 expected; SMR 1.2; 95% CI 0.9–1.6) but little excess in suicides (11 observed, 10.2 expected; SMR 1.1; 95% CI 0.5–1.9).Conclusions/interpretationBefore the onset of late complications, significant excess mortality existed following the diagnosis of type 1 diabetes in childhood, even in recent years. Variation between countries in this excess could not be explained.

Serum 25(OH)D and Type 2 Diabetes Association in a General Population: A prospective study

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.

Improved metabolic outcome in a Danish diabetic paediatric population aged 0-18 yr: results from a nationwide continuous Registration.

OBJECTIVE This study aimed to examine vitamin D status as a determinant for development of type 2 diabetes and deterioration of glucose homeostasis. RESEARCH DESIGN AND METHODS A random sample of the general population of Copenhagen, Denmark, was taken as part of the Inter99 study. Included were 6,405 men and women aged 30–65 years at baseline (1999–2001), with 4,296 participating in the follow-up examination 5 years later (2004–2006). Vitamin D was determined at baseline as serum 25-hydroxyvitamin D [25(OH)D]. Diabetes was defined based on an oral glucose tolerance test and a glycosylated hemoglobin (HbA1c) test. Secondary outcomes included continuous markers of glucose homeostasis. RESULTS The risk of incident diabetes associated with a 10 nmol/L increase in 25(OH)D was odds ratio (OR) 0.91 (95% CI 0.84–0.97) in crude analyses. The association became statistically nonsignificant after adjustment for confounders, with an OR per 10 nmol/L of 0.94 (0.86–1.03). Low 25(OH)D status was significantly associated with unfavorable longitudinal changes in continuous markers of glucose homeostasis after adjustment for confounders. Fasting and 2-h glucose and insulin as well as the degree of insulin resistance increased significantly more during follow-up among those with low 25(OH)D levels compared with those with higher levels. CONCLUSIONS Low 25(OH)D status was not significantly associated with incident diabetes after adjustment for confounders. However, it was significantly associated with unfavorable longitudinal changes in continuous markers of glucose homeostasis, indicating that low vitamin D status could be related to deterioration of glucose homeostasis.

Breast-Feeding and Childhood-Onset Type 1 Diabetes: A pooled analysis of individual participant data from 43 observational studies

The objective of the present study was to describe the changes in glycaemic control based on data from the nationwide Danish Registry of Childhood Diabetes with valid haemoglobin A1c (HbA1c) readings centrally analysed between 1996 and 2006. The glycaemic control was assessed using generalized linear mixed models. Centre, age, diabetes duration, ethnicity, sex, self‐monitoring of blood glucose, insulin regimens and hypoglycaemia was tested as explanatory variables. There were 9291 HbA1c recordings from 2705 children with T1D during the 10‐yr period. The unadjusted mean HbA1c value in 1997 was 9.05% (95% CI ± 0.82) and in 2006 was 8.20% (95% CI ± 0.06). Mean HbA1c was significantly reduced over the years with a linear decrease of 0.08% per year (95% CI ±0.011) (p < 0.0001). The decrease was unaffected by adjusting for number of injections, insulin/kg and use of insulin analogous. During the period, an increased frequency of self‐monitored blood glucose was observed that was associated with a reduction in HbA1c (p < 0.0001). The percentage of children with severe hypoglycaemia decreased from 12.2 to 7.8% in those with HbA1c between 6 and 8%. Metabolic control in diabetic children has improved on a nationwide basis from the establishment of the national registry in 1996. The reduction in HbA1c was related to an increased number of self‐monitoring of blood glucose values and a decrease in the number of hypoglycaemic events in those with the best metabolic control, whereas there were no association with the use of new analogous or insulin regimens.

Maternal Age at Birth and Childhood Type 1 Diabetes: A Pooled Analysis of 30 Observational Studies

OBJECTIVE To investigate if there is a reduced risk of type 1 diabetes in children breastfed or exclusively breastfed by performing a pooled analysis with adjustment for recognized confounders. RESEARCH DESIGN AND METHODS Relevant studies were identified from literature searches using MEDLINE, Web of Science, and EMBASE. Authors of relevant studies were asked to provide individual participant data or conduct prespecified analyses. Meta-analysis techniques were used to combine odds ratios (ORs) and investigate heterogeneity between studies. RESULTS Data were available from 43 studies including 9,874 patients with type 1 diabetes. Overall, there was a reduction in the risk of diabetes after exclusive breast-feeding for >2 weeks (20 studies; OR = 0.75, 95% CI 0.64–0.88), the association after exclusive breast-feeding for >3 months was weaker (30 studies; OR = 0.87, 95% CI 0.75–1.00), and no association was observed after (nonexclusive) breast-feeding for >2 weeks (28 studies; OR = 0.93, 95% CI 0.81–1.07) or >3 months (29 studies; OR = 0.88, 95% CI 0.78–1.00). These associations were all subject to marked heterogeneity (I2 = 58, 76, 54, and 68%, respectively). In studies with lower risk of bias, the reduced risk after exclusive breast-feeding for >2 weeks remained (12 studies; OR = 0.86, 95% CI 0.75–0.99), and heterogeneity was reduced (I2 = 0%). Adjustments for potential confounders altered these estimates very little. CONCLUSIONS The pooled analysis suggests weak protective associations between exclusive breast-feeding and type 1 diabetes risk. However, these findings are difficult to interpret because of the marked variation in effect and possible biases (particularly recall bias) inherent in the included studies.

Remission without insulin therapy on gluten-free diet in a 6-year old boy with type 1 diabetes mellitus.

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 I2 = 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 order and childhood type 1 diabetes risk: a pooled analysis of 31 observational studies

A 5-year and 10-month old boy was diagnosed with classical type 1 diabetes mellitus (T1DM) without celiac disease. He started on a gluten-free diet after 2–3 week without need of insulin treatment. At the initiation of gluten-free diet, HbA1c was 7.8% and was stabilised at 5.8%–6.0% without insulin therapy. Fasting blood glucose was maintained at 4.0–5.0 mmol/l. At 16 months after diagnosis the fasting blood glucose was 4.1 mmol/l and after 20 months he is still without daily insulin therapy. There was no alteration in glutamic acid decarboxylase positivity. The gluten-free diet was safe and without side effects. The authors propose that the gluten-free diet has prolonged remission in this patient with T1DM and that further trials are indicated.