The incidence of childhood-onset type 1 diabetes, time trends and association with the population composition in Sweden: a 40 year follow-up

AIMS/HYPOTHESIS

During the 1980s and 1990s, the incidence of childhood-onset type 1 diabetes more than doubled in Sweden, followed by a plateau. In the present 40 year follow-up, we investigated if the incidence remained stable and whether this could be explained by increased migration from countries reporting lower incidences.

METHODS

We used 23,143 incident cases of childhood-onset type 1 diabetes reported between 1978 and 2019 to the nationwide, population-based Swedish Childhood Diabetes Registry and population data from Statistics Sweden. Generalised additive models and ANOVA were applied to analyse the effects of onset age, sex, time trends and parental country of birth and interaction effects between these factors.

RESULTS

The flattening of the incidence increase seems to remain over the period 2005-2019. When comparing the incidence of type 1 diabetes for all children in Sweden with that for children with both parents born in Sweden, the trends were parallel but at a higher level for the latter. A comparison of the incidence trends between individuals with Swedish backgrounds (high diabetes trait) and Asian backgrounds (low diabetes trait) showed that the Asian subpopulation had a stable increase in incidence over time.

CONCLUSIONS/INTERPRETATION

In Sweden, the increase in incidence of childhood-onset type 1 diabetes in the late 20th century has been approaching a more stable albeit high level over the last two decades. Increased immigration from countries with lower incidences of childhood-onset type 1 diabetes does not provide a complete explanation for the observed levelling off.

Risk of cancer in young and middle-aged adults with childhood-onset type 1 diabetes in Sweden-A prospective cohort study

AIMS/HYPOTHESIS

In persons with type 1 diabetes, the risk of cancer remains controversial. We wanted to examine the excess risk of cancer in a large population-based cohort diagnosed with type 1 diabetes before 15 years of age.

STUDY POPULATION AND METHODS

From 1 July 1977 to 31 December 2013, we prospectively and on a national scale included 18,724 persons (53% men) with childhood-onset type 1 diabetes. For each person with type 1 diabetes, we selected four referents, matched for the date at birth and municipality of living at the time when the case developed diabetes. Cases and referents were linked to national registers of cancer and of the cause of death.

RESULTS

A total of 125 persons (61% women) with diabetes had 135 different cancers, all diagnosed after the diabetes diagnosis. The median duration from diabetes diagnosis to first cancer diagnosis was 19 years (interquartile range 10-26). The median age at cancer diagnosis in the diabetes group was 28 years (interquartile range 20-35). The overall standardized incidence ratio (95%), using the Swedish general population as referents for women with diabetes was 1.28 (1.02, 1.58) and when comparing women with diabetes with matched referents, we found a hazard ratio of 1.42 (1.10, 1.85). No elevated risk was seen for men. Cancers of the breast and testis were the most common types in women and men respectively.

CONCLUSIONS

Women with childhood-onset type 1 diabetes had a small but significantly elevated risk of cancer. No such tendency was seen for men. The reason behind this is unclear.

Worldwide estimates of incidence, prevalence and mortality of type 1 diabetes in children and adolescents: Results from the International Diabetes Federation Diabetes Atlas, 9th edition

AIMS

This article describes the methods, results and limitations of the International Diabetes Federation (IDF) Diabetes Atlas 9th edition estimates of worldwide numbers of cases of type 1 diabetes in children and adolescents.

METHODS

Most information in the published literature is in the form of incidence rates derived from registers of newly-diagnosed cases. After systematic review of the published literature and recent conference abstracts, identified studies were quality graded. If no study was available, extrapolation was used to assign a country the rate from an adjacent country with similar characteristics. Estimates of incident cases were obtained by applying incidence rates to United Nations 2019 population estimates. Estimates of prevalent cases were derived from incidence rates after making allowance for higher mortality rates in less-developed countries.

RESULTS

Incidence rates were available for 45% of countries (ranging from 6% in the sub-Saharan Africa region to 77% in the European region). Worldwide annual incidence estimates were 98,200 (128,900) new cases in the under 15 year (under 20 year) age-groups. Corresponding prevalence estimates were 600,900 (1,110,100) existing cases. Compared with estimates in earlier Atlas editions, numbers have increased in most IDF regions, reflecting incidence rate increases, but prevalence estimates have decreased in sub-Saharan Africa because allowance has been made for increased mortality in those with diabetes.

CONCLUSIONS

Worldwide estimates of numbers of children and adolescents with type 1 diabetes continue to increase.

Perinatal risk factors for type 1 diabetes revisited: a population-based register study

AIMS/HYPOTHESIS

Single-centre studies and meta-analyses have found diverging results as to which early life factors affect the risk of type 1 diabetes during childhood. We wanted to use a large, nationwide, prospective database to further clarify and analyse the associations between perinatal factors and the subsequent risk for childhood-onset type 1 diabetes using a case-control design.

METHODS

The Swedish Childhood Diabetes Register was linked to the Swedish Medical Birth Register and National Patient Register, and 14,949 cases with type 1 diabetes onset at ages 0-14 years were compared with 55,712 matched controls born from the start of the Medical Birth Register in 1973 to 2013. After excluding confounders (i.e. children multiple births, those whose mother had maternal diabetes and those with a non-Nordic mother), we used conditional logistic regression analyses to determine risk factors for childhood-onset type 1 diabetes. We used WHO ICD codes for child and maternal diagnoses.

RESULTS

In multivariate analysis, there were small but statistically significant associations between higher birthweight z score (OR 1.08, 95% CI 1.06, 1.10), delivery by Caesarean section (OR 1.08, 95% CI 1.02, 1.15), premature rupture of membranes (OR 1.08, 95% CI 1.01, 1.16) and maternal urinary tract infection during pregnancy (OR 1.39, 95% CI 1.04, 1.86) and the subsequent risk of childhood-onset type 1 diabetes. Birth before 32 weeks of gestation was associated with a lower risk of childhood-onset type 1 diabetes compared with full-term infants (OR 0.54, 95% CI 0.38, 0.76), whereas birth between 32 and 36 weeks' gestation was associated with a higher risk (OR 1.24, 95% CI 1.14, 1.35). In subgroup analyses (birth years 1992-2013), maternal obesity was independently associated with subsequent type 1 diabetes in the children (OR 1.27, 95% CI 1.15, 1.41) and rendered the association with Caesarean section non-significant. In contrast to previous studies, we found no association of childhood-onset type 1 diabetes with maternal-child blood-group incompatibility, maternal pre-eclampsia, perinatal infections or treatment of the newborn with phototherapy for neonatal jaundice. The proportion of children with neonatal jaundice was significantly higher in the 1973-1982 birth cohort compared with later cohorts.

CONCLUSIONS/INTERPRETATION

Perinatal factors make small but statistically significant contributions to the overall risk of childhood-onset type 1 diabetes. Some of these risk factors, such as maternal obesity, may be amendable with improved antenatal care. Better perinatal practices may have affected some previously noted risk factors over time.

Trends and cyclical variation in the incidence of childhood type 1 diabetes in 26 European centres in the 25 year period 1989-2013: a multicentre prospective registration study

AIMS/HYPOTHESIS

Against a background of a near-universally increasing incidence of childhood type 1 diabetes, recent reports from some countries suggest a slowing in this increase. Occasional reports also describe cyclical variations in incidence, with periodicities of between 4 and 6 years.

METHODS

Age/sex-standardised incidence rates for the 0- to 14-year-old age group are reported for 26 European centres (representing 22 countries) that have registered newly diagnosed individuals in geographically defined regions for up to 25 years during the period 1989-2013. Poisson regression was used to estimate rates of increase and test for cyclical patterns. Joinpoint regression software was used to fit segmented log-linear relationships to incidence trends.

RESULTS

Significant increases in incidence were noted in all but two small centres, with a maximum rate of increase of 6.6% per annum in a Polish centre. Several centres in high-incidence countries showed reducing rates of increase in more recent years. Despite this, a pooled analysis across all centres revealed a 3.4% (95% CI 2.8%, 3.9%) per annum increase in incidence rate, although there was some suggestion of a reduced rate of increase in the 2004-2008 period. Rates of increase were similar in boys and girls in the 0- to 4-year-old age group (3.7% and 3.7% per annum, respectively) and in the 5- to 9-year-old age group (3.4% and 3.7% per annum, respectively), but were higher in boys than girls in the 10- to 14-year-old age group (3.3% and 2.6% per annum, respectively). Significant 4 year periodicity was detected in four centres, with three centres showing that the most recent peak in fitted rates occurred in 2012.

CONCLUSIONS/INTERPRETATION

Despite reductions in the rate of increase in some high-risk countries, the pooled estimate across centres continues to show a 3.4% increase per annum in incidence rate, suggesting a doubling in incidence rate within approximately 20 years in Europe. Although four centres showed support for a cyclical pattern of incidence with a 4 year periodicity, no plausible explanation for this can be given.

Decreasing Cumulative Incidence of End-Stage Renal Disease in Young Patients With Type 1 Diabetes in Sweden: A 38-Year Prospective Nationwide Study

OBJECTIVE

Diabetic nephropathy is a serious complication of type 1 diabetes. Recent studies indicate that end-stage renal disease (ESRD) incidence has decreased or that the onset of ESRD has been postponed; therefore, we wanted to analyze the incidence and time trends of ESRD in Sweden.

RESEARCH DESIGN AND METHODS

In this study, patients with duration of type 1 diabetes >14 years and age at onset of diabetes 0-34 years were included. Three national diabetes registers were used: the Swedish Childhood Diabetes Register, the Diabetes Incidence Study in Sweden, and the National Diabetes Register. The Swedish Renal Registry, a national register on renal replacement therapy, was used to identify patients who developed ESRD.

RESULTS

We found that the cumulative incidence of ESRD in Sweden was low after up to 38 years of diabetes duration (5.6%). The incidence of ESRD was lower in patients with type 1 diabetes onset in 1991-2001 compared with onset in 1977-1984 and 1985-1990, independent of diabetes duration.

CONCLUSIONS

The risk of developing ESRD in Sweden in this population is still low and also seems to decrease with time.

Why childhood-onset type 1 diabetes impacts labour market outcomes: a mediation analysis

AIMS/HYPOTHESIS

Previous studies show a negative effect of type 1 diabetes on labour market outcomes such as employment and earnings later in life. However, little is known about the mechanisms underlying these effects. This study aims to analyse the mediating role of adult health, education, occupation and family formation.

METHODS

A total of 4179 individuals from the Swedish Childhood Diabetes Register and 16,983 individuals forming a population control group born between 1962 and 1979 were followed between 30 and 50 years of age. The total effect of having type 1 diabetes was broken down into a direct effect and an indirect (mediating) effect using statistical mediation analysis. We also analysed whether type 1 diabetes has different effects on labour market outcome between the sexes and across socioeconomic status.

RESULTS

Childhood-onset type 1 diabetes had a negative impact on employment (OR 0.68 [95% CI 0.62, 0.76] and OR 0.76 [95% CI 0.67, 0.86]) and earnings (-6%, p < 0.001 and -8%, p < 0.001) for women and men, respectively. Each of the mediators studied contributed to the total effect with adult health and occupational field accounting for the largest part. However, some of the effect could not be attributed to any of the mediators studied and was therefore likely related to other characteristics of the disease that hamper career opportunities. The effect of type 1 diabetes on employment and earnings did not vary significantly according to socioeconomic status of the family (parental education and earnings).

CONCLUSIONS/INTERPRETATION

A large part of the effect of type 1 diabetes on the labour market is attributed to adult health but there are other important mediating factors that need to be considered to reduce this negative effect.

Socio-economic factors influencing the development of end-stage renal disease in people with Type 1 diabetes - a longitudinal population study

AIMS

The development of end-stage renal disease (ESRD) in Type 1 diabetes is multifactorial. Familial socio-economic factors may influence adherence to and understanding of diabetes treatment, and also general health behaviour. We investigate how parental and personal education level and exposure to low economic status, indicated by the need for income support, influence the development of ERSD caused by Type 1 diabetes.

METHODS

Participants were retrieved from the nationwide Swedish Childhood Diabetes Registry, which was linked to the Swedish Renal Registry, to find people with ESRD caused by Type 1 diabetes, and to Statistic Sweden to retrieve longitudinal socio-economic data on participants and their parents. Data were analysed using Cox regression modelling.

RESULTS

Of 9287 people with diabetes of duration longer than 14 years, 154 had developed ESRD due to diabetes. Median diabetes duration (range) for all participants was 24.2 years (14.0-36.7 years). Low maternal education (≤ 12 years) more than doubled the risk of developing ESRD, hazard ration (HR) = 2.9 [95% confidence interval (95% CI): 1.7-4.8]. For people with a low personal level of education HR was 5.7 (3.4-9.5). In an adjusted model, the person's own education level had the highest impact on the risk of ESRD. If at least one of the parents had ever received income support the HR was 2.6 (1.9-3.6).

CONCLUSIONS

Socio-economic factors, both for the parents and the person with diabetes, have a strong influence on the development of ESRD in Type 1 diabetes. It is important for caregivers to give enough support to more vulnerable people and their families.

Impact of parental socioeconomic status on excess mortality in a population-based cohort of subjects with childhood-onset type 1 diabetes

OBJECTIVE

The aim of this study was to analyze the possible impact of parental and individual socioeconomic status (SES) on all-cause mortality in a population-based cohort of patients with childhood-onset type 1 diabetes.

RESEARCH DESIGN AND METHODS

Subjects recorded in the Swedish Childhood Diabetes Registry (SCDR) from 1 January 1978 to 31 December 2008 were included (n = 14,647). The SCDR was linked to the Swedish Cause of Death Registry (CDR) and the Longitudinal Integration Database for Health Insurance and Labour Market Studies (LISA).

RESULTS

At a mean follow-up of 23.9 years (maximum 46.5 years), 238 deaths occurred in a total of 349,762 person-years at risk. In crude analyses, low maternal education predicted mortality for male patients only (P = 0.046), whereas parental income support predicted mortality in both sexes (P < 0.001 for both). In Cox models stratified by age-at-death group and adjusted for age at onset and sex, parental income support predicted mortality among young adults (≥18 years of age) but not for children. Including the adult patient's own SES in a Cox model showed that individual income support to the patient predicted mortality occurring at ≥24 years of age when adjusting for age at onset, sex, and parental SES.

CONCLUSIONS

Exposure to low SES, mirrored by the need for income support, increases mortality risk in patients with childhood-onset type 1 diabetes who died after the age of 18 years.

Five-region study finds no evidence of undiagnosed type 2 diabetes in Swedish 11- to 13-year-olds

AIM

Childhood obesity is now an established public health problem in most developed countries, and there is concern about a parallel increase of type 2 diabetes. The aim of this study was to estimate the prevalence of undiagnosed type 2 diabetes in overweight Swedish school children from 11 to 13 years of age.

METHODS

Body mass index (BMI) was measured in 5528 schoolchildren in the 6th grade, from 11 to 13 years of age, in five different regions in Sweden. Overweight was defined by international age- and sex-specific BMI cut-offs, corresponding to adult BMI cut-offs of 25 kg/m(2) at 18 years of age (ISO-BMI ≥25, n = 1275). Haemoglobin A1c (HbA1c) was measured in 1126 children with ISO-BMI ≥25. Children with a Diabetes Control and Complications Trial aligned HbA1c ≥6.1% on two occasions underwent an oral glucose tolerance test (OGTT) to establish the diabetes diagnosis.

RESULTS

Of 1126 children with ISO-BMI ≥25, 24 (2.1%) had at least one HbA1c value ≥6.1%. Three of them had HbA1c ≥6.1% on two occasions, and all of them had a normal OGTT.

CONCLUSION

In this cross-sectional, population-based screening study of a high-risk group of 11- to 13-year-old Swedish school children, we found no indication of undiagnosed diabetes or impaired glucose tolerance.

Renal replacement therapy due to type 1 diabetes; time trends during 1995-2010--a Swedish population based register study

BACKGROUND

End stage renal disease (ESRD), is the most severe complication of diabetes mellitus. This population-based study analysed time trends for start of renal replacement therapy (RRT) due to type 1 diabetes compared to type 2 diabetes and other diagnoses.

MATERIAL AND METHODS

We used data on patients who were registered 1995-2010 in the Swedish Renal Registry, a nationwide register covering 95 % of all patients with uraemia. The patients were analysed according to their original kidney disease. The incidence was analysed by calendar year, age at start of RRT and gender.

RESULTS

Of 17389 patients who were registered, 1833 had type 1 diabetes; 65% were men. The mean age at onset of RRT for patients with type 1 diabetes was 52.8 years which increased by more than 3 years over the studied period. The number of patients in need of RRT due to type 1 diabetes decreased, while RRT due to type 2 diabetes increased during the period studied.

CONCLUSIONS

The overall incidence of RRT in Sweden is rather constant over the years but the need for RRT in type 1 diabetes patients decreased and patients with type 1 diabetes tend to become older at onset of RRT.

Diabetes in the young - a global view and worldwide estimates of numbers of children with type 1 diabetes

This paper describes the methodology, results and limitations of the 2013 International Diabetes Federation (IDF) Atlas (6th edition) estimates of the worldwide numbers of prevalent cases of type 1 diabetes in children (<15 years). The majority of relevant information in the published literature is in the form of incidence rates derived from registers of newly diagnosed cases. Studies were graded on quality criteria and, if no information was available in the published literature, extrapolation was used to assign a country the rate from an adjacent country with similar characteristics. Prevalence rates were then derived from these incidence rates and applied to United Nations 2012 Revision population estimates for 2013 for each country to obtain estimates of the number of prevalent cases. Data availability was highest for the countries in Europe (76%) and lowest for the countries in sub-Saharan Africa (8%). The prevalence estimates indicate that there are almost 500,000 children aged under 15 years with type 1 diabetes worldwide, the largest numbers being in Europe (129,000) and North America (108,700). Countries with the highest estimated numbers of new cases annually were the United States (13,000), India (10,900) and Brazil (5000). Compared with the prevalence estimates made in previous editions of the IDF Diabetes Atlas, the numbers have increased in most of the IDF Regions, often reflecting the incidence rate increases that have been well-documented in many countries. Monogenic diabetes is increasingly being recognised among those with clinical features of type 1 or type 2 diabetes as genetic studies become available, but population-based data on incidence and prevalence show wide variation due to lack of standardisation in the studies. Similarly, studies on type 2 diabetes in childhood suggest increased incidence and prevalence in many countries, especially in Indigenous peoples and ethnic minorities, but detailed population-based studies remain limited.

Impact of childhood-onset type 1 diabetes on schooling: a population-based register study

AIMS/HYPOTHESIS

We investigated the impact of type 1 diabetes on educational achievements in compulsory and upper secondary school, as well as potential long-lasting effects.

METHODS

Altogether 2,485 individuals with type 1 diabetes, diagnosed at the age of <15 years and born in 1972-1978, were selected from the Swedish Childhood Diabetes Register, which was linked to national population registers including the Swedish Education Register. For each individual, four controls from the general population, matched for year of birth and residence at the time of diagnosis, were selected by Statistics Sweden (n = 9,940). We analysed the impact of diabetes on final school grades at 16 years (compulsory school) and 19 years (upper secondary school) and on participation in the labour market at 29 years using linear, logistic, ordered logistic and quantile regression analyses, controlling for demographics and socioeconomic background.

RESULTS

Diabetes had a negative effect on mean final grades (scale of 1-5) in compulsory school (-0.07, p < 0.001) and theoretical programmes in upper secondary school (-0.07, p = 0.001). Children with early-onset diabetes (0-4 years) suffered a greater disadvantage as a result of the disease (-0.15, p = 0.001 in compulsory school). The strongest effect was seen in the lowest deciles of the conditional distribution on mean final grades. At age 29, individuals with diabetes were less likely to be gainfully employed (OR 0.82, 95% CI 0.73, 0.91).

CONCLUSIONS/INTERPRETATION

The small but significant negative effect of type 1 diabetes on schooling could affect opportunities for further education and career development. Attention must be paid in school to the special needs of children with diabetes.

Socioeconomic factors, rather than diabetes mellitus per se, contribute to an excessive use of antidepressants among young adults with childhood onset type 1 diabetes mellitus: a register-based study

AIMS/HYPOTHESIS

Mood disorders, including depression, are suggested to be prevalent in persons with type 1 diabetes and may negatively affect self-management and glycaemic control and increase the risk of diabetic complications. The aim of this study was to analyse the prevalence of antidepressant (AD) use in adults with childhood onset type 1 diabetes and to compare risk determinants for AD prescription among diabetic patients and a group of matched controls.

METHODS

Young adults ≥ 18 years on 1 January 2006 with type 1 diabetes (n = 7,411) were retrieved from the population-based Swedish Childhood Diabetes Registry (SCDR) and compared with 30,043 age- and community-matched controls. Individual level data were collected from the Swedish National Drug Register (NDR), the Hospital Discharge Register (HDR) and the Labor Market Research database (LMR).

RESULTS

ADs were prescribed to 9.5% and 6.8% of the type 1 diabetes and control subjects, respectively. Female sex, having received economic or other social support, or having a disability pension were the factors with the strongest association with AD prescription in both groups. Type 1 diabetes was associated with a 44% (OR 1.44, 95% CI 1.32, 1.58) higher risk of being prescribed ADs in crude analysis. When adjusting for potential confounders including sex, age and various socioeconomic risk factors, this risk increase was statistically non-significant (OR 1.11, 95% CI 0.99, 1.21).

CONCLUSIONS/INTERPRETATION

The risk factor patterns for AD use are similar among type 1 diabetic patients and controls, and socioeconomic risk factors, rather than the diabetes per se, contribute to the increased risk of AD use in young adults with type 1 diabetes.

Thirty years of prospective nationwide incidence of childhood type 1 diabetes: the accelerating increase by time tends to level off in Sweden

OBJECTIVE

During the past few decades, a rapidly increasing incidence of childhood type 1 diabetes (T1D) has been reported from many parts of the world. The change over time has been partly explained by changes in lifestyle causing rapid early growth and weight development. The current study models and analyzes the time trend by age, sex, and birth cohort in an exceptionally large study group.

RESEARCH DESIGN AND METHODS

The present analysis involved 14,721 incident cases of T1D with an onset of 0-14.9 years that were recorded in the nationwide Swedish Childhood Diabetes Registry from 1978 to 2007. Data were analyzed using generalized additive models.

RESULTS

Age- and sex-specific incidence rates varied from 21.6 (95% CI 19.4-23.9) during 1978-1980 to 43.9 (95% CI 40.7-47.3) during 2005-2007. Cumulative incidence by birth cohort shifted to a younger age at onset during the first 22 years, but from the birth year 2000 a statistically significant reversed trend (P < 0.01) was seen.

CONCLUSIONS

Childhood T1D increased dramatically and shifted to a younger age at onset the first 22 years of the study period. We report a reversed trend, starting in 2000, indicating a change in nongenetic risk factors affecting specifically young children.

Cumulative risk, age at onset, and sex-specific differences for developing end-stage renal disease in young patients with type 1 diabetes: a nationwide population-based cohort study

OBJECTIVE

This study aimed to estimate the current cumulative risk of end-stage renal disease (ESRD) due to diabetic nephropathy in a large, nationwide, population-based prospective type 1 diabetes cohort and specifically study the effects of sex and age at onset.

RESEARCH DESIGN AND METHODS

In Sweden, all incident cases of type 1 diabetes aged 0-14 years and 15-34 years are recorded in validated research registers since 1977 and 1983, respectively. These registers were linked to the Swedish Renal Registry, which, since 1991, collects data on patients who receive active uremia treatment. Patients with > or =13 years duration of type 1 diabetes were included (n = 11,681).

RESULTS

During a median time of follow-up of 20 years, 127 patients had developed ESRD due to diabetic nephropathy. The cumulative incidence at 30 years of type 1 diabetes duration was low, with a male predominance (4.1% [95% CI 3.1-5.3] vs. 2.5% [1.7-3.5]). In both male and female subjects, onset of type 1 diabetes before 10 years of age was associated with the lowest risk of developing ESRD. The highest risk of ESRD was found in male subjects diagnosed at age 20-34 years (hazard ratio 3.0 [95% CI 1.5-5.7]). In female subjects with onset at age 20-34 years, the risk was similar to patients' diagnosed before age 10 years.

CONCLUSIONS

The cumulative incidence of ESRD is exceptionally low in young type 1 diabetic patients in Sweden. There is a striking difference in risk for male compared with female patients. The different patterns of risk by age at onset and sex suggest a role for puberty and sex hormones.

Confirmed association between neonatal phototherapy or neonatal icterus and risk of childhood asthma

We have previously demonstrated an association between neonatal phototherapy and/or neonatal icterus and risk of hospitalization for childhood asthma. This study included children who were prescribed anti-asthmatic medication on a population basis to study exposures during the foetal and neonatal period and risk of childhood asthma. The Swedish Medical Birth Register was linked to the Swedish Prescribed Drug Register. Perinatal data for singleton children who were prescribed anti-asthmatic medication (n = 61,256) were compared with corresponding data for all singleton children born in Sweden from 1 January 1990 to 30 June 2003 and surviving to 1 July 2005 (n = 1,338,319). Mantel-Haenszel's odds ratios were calculated after adjustment for various known confounders. Being the first-born child, maternal age above 44 yr, involuntary childlessness for more than 1 yr, maternal smoking during pregnancy, maternal diabetes mellitus of any kind, pre-eclampsia, caesarean section, and instrumental vaginal delivery were all associated with an increased prescription of anti-asthmatic medication during childhood. Preterm birth, low birth weight, being small for gestational age, respiratory problems, mechanical ventilation, and sepsis and/or pneumonia were also associated with increased drug prescriptions. Neonatal phototherapy and/or icterus were risk determinants for children who developed asthma before the age of 12. After controlling for confounders, the odds ratio for phototherapy and/or icterus remained at 1.30 (95% confidence interval 1.16-1.47). In conclusion, this large population-based study confirms an association between some maternal and perinatal factors and childhood asthma, including neonatal phototherapy and/or icterus.

The effect of polymorphisms in the renin-angiotensin-aldosterone system on diabetic nephropathy risk

OBJECTIVES

The risk of diabetic nephropathy (DN) can be increased by elevated intraglomerular pressure and glomerular filtration rate, leading to glomerular damage. This can be controlled by the renin-angiotensin-aldosterone (RAA) system, which has an important function regulating both systemic and intrarenal blood pressure. Smoking increases the risk of DN, but not all diabetic patients who smoke develop DN. There is a possibility that smoking has different effects depending on the different genotypes of the individual. We investigated the association of DN with seven polymorphisms in the RAA system and their possible interaction with smoking.

SUBJECTS AND METHODS

In the present case-control study, type 1 diabetic patients with diabetes duration > or =20 years, without albuminuria and without antihypertensive treatment (n=197), were included as controls. An albumin excretion rate (AER) of 20-200 microg/min (n=73) was considered as incipient DN, and an AER >200 microg/min was considered as overt DN (n=48). Smoking habits were obtained from questionnaires.

RESULTS

Homozygosity for the A allele, of the angiotensin II type 1 receptor (AGTR1) A1166C polymorphism, was associated with increased risk of overt DN (OR=3.04; 99% CI=1.02-9.06), independently of the other associated variables: age, duration of diabetes, ever smoking, HbA1c, and sex. The effect of the AA genotype was enhanced to a four times risk increase among ever-smoking patients. Two alleles of the microsatellite marker adjacent to the angiotensinogen gene were less common among nephropathy cases than among controls, but this was not significant when controlling for the same variables as above.

CONCLUSIONS

The risk of having overt DN was increased in patients homozygous for the A1166 allele, and smoking seemed to enhance the effect of the AGTR1 genotype.

Hospitalization for vascular complications in childhood onset type 1 diabetes--effects of gender and age at onset

AIMS

To study the cumulative incidence of hospitalization for severe diabetic vascular complications in childhood onset type 1 diabetes patients with special regards to age at onset and gender.

METHODS

The Swedish Childhood Diabetes Register (SCDR) was linked to the Swedish Hospital Discharge Register up to 31 December 2004. The following diagnoses were traced: diabetic kidney disease, myocardial infarction, stroke, lower limb arterial disease and diabetes with multiple complications. Cox proportional hazards survival method was applied with the following covariates: maternal age, birthweight deviation from gestational week standard, age at onset and gender.

RESULTS

Until 31 December 9974 children had been followed for at least 10 years corresponding to 141 839 person years at risk and 103 (7.3 per 1000 person years) had been hospitalized at least once at the maximum duration of follow-up of 26 years. Diabetic kidney disease was the most common cause of hospitalization and 63 patients had more than one diabetic complication. Female gender (RR=2.02, 95% CI=1.05-3.89) and age at onset of diabetes (RR=1.37, 95% CI=1.20-1.56) were significant risk factors for severe complication.

CONCLUSIONS

Hospitalization for severe diabetic complications at a maximum follow-up of 26 years is rather low in Sweden. There is a higher hospitalization rate among females than among males, and also among patients diagnosed with diabetes after 10 years of age than among patients diagnosed before the age of 10 years.

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

AIMS/HYPOTHESIS

The 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.

METHODS

Thirteen 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.

RESULTS

There 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$ 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/INTERPRETATION

Before 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.

Distribution of neuropeptide Y Leu7Pro polymorphism in patients with type 1 diabetes and diabetic nephropathy among Swedish and American populations

OBJECTIVE

The distribution of Leu7Pro polymorphism in the neuropeptide Y gene shows a geographical north to south gradient of decreasing frequency, suggesting that it may be a population-specific causal variant. This polymorphism is found to be associated with diabetic nephropathy (DN) and coronary heart disease in Finnish women with type 1 diabetes (T1D). The present study aims to evaluate the susceptibility of this polymorphism to the development of DN in two different populations.

DESIGN

One sample set consists of 174 (females 98 and males 76) Swedish T1D patients with DN and 249 (females 132 and males 117) patients without DN. Another sample set includes 597 (females 356 and males 241) American T1D patients without DN and 577 (females 264 and males 313) patients with DN, who were descents of European Caucasians and were from the Genetics of Kidneys in Diabetes (GoKinD) Study.

METHODS

Genotyping of Leu7Pro polymorphism was performed by dynamic allele-specific hybridization.

RESULTS

The C allele frequencies of Leu7Pro polymorphism in T1D patients between Swedish and American GoKinD populations were significantly different (6.3 vs 4.0%; P=0.006). Particularly, the C allele frequency in Swedish female T1D patients with DN was significantly higher in comparison with T1D patients without DN (10.2 vs 4.2%; P=0.011, OR=2.614, 95% confidence intervals: 1.249-5.467). No significant association of this polymorphism with DN was observed in Swedish male T1D patients and the patients from GoKinD.

CONCLUSIONS

The present study provides further evidence that Leu7Pro polymorphism confers the susceptibility to the development of DN in Swedish female T1D patients.

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.

School marks for Swedish children whose mothers had diabetes during pregnancy: a population-based study

AIMS/HYPOTHESIS

To study, at a population level, school performance when leaving compulsory school of Swedish children whose mothers had diabetes during pregnancy compared with a reference population.

METHODS

We linked the Swedish Medical Birth Register with the Swedish School Mark Register, which contains school marks for all children in Sweden when leaving compulsory school. A total of 6,397 children were identified whose mothers had a diagnosis of diabetes during pregnancy in the years 1973 to 1986. Data on these children were compared with 1,300,683 children whose mothers had no diagnosis of diabetes during pregnancy. Risks were estimated as odd ratios (ORs) after adjustment for year of birth, maternal age, parity and educational level of the mother.

RESULTS

The children's average numerical school marks (for children leaving school between 1988 and 1997) were statistically significantly lower among children born to mothers with diabetes in pregnancy compared with reference children (3.13 +/- 0.01 vs 3.23, p < 0.001). The effect was similar among boys and girls. There was also an effect of maternal diabetes during pregnancy on the risk of the child not completing compulsory school (OR 1.25; 95% CI 1.10-1.43, and after exclusion of infants with certain perinatal characteristics an OR of 1.25; 95% CI 1.02-1.53). When sports and the core subjects mathematics, English and Swedish were studied, there were increased risks of having scores below pass level and decreased probabilities of having scores above pass level for children of mothers with diabetes during pregnancy.

CONCLUSIONS/INTERPRETATION

Children of mothers with diabetes during pregnancy performed slightly but significantly less well than reference children when leaving compulsory school at about 16 years old; this was also seen after adjustment for some putative perinatal and social confounders.

SUMO4 M55V polymorphism affects susceptibility to type I diabetes in HLA DR3- and DR4-positive Swedish patients

SUMO4 M55V, located in IDDM5, has been a focus for debate because of its association to type I diabetes (TIDM) in Asians but not in Caucasians. The current study aims to test the significance of M55V association to TIDM in a large cohort of Swedish Caucasians, and to test whether M55V is associated in those carrying human leukocyte antigen (HLA) class II molecules. A total of 673 TIDM patients and 535 age- and sex-matched healthy controls were included in the study. PCR-RFLP was performed to identify the genotype and allele variations. Our data suggest that SUMO4 M55V is not associated with susceptibility to TIDM by itself. When we stratified our patients and controls based on heterozygosity for HLA-DR3/DR4 and SUMO4 genotypes, we found that presence of SUMO4 GG increased further the relative risk conferred by HLA-DR3/DR4 to TIDM, whereas SUMO4 AA decreased the risk. From the current study, we conclude that SUMO4 M55V is associated with TIDM in association with high-risk HLA-DR3 and DR4, but not by itself.

Is neonatal phototherapy associated with an increased risk for hospitalized childhood bronchial asthma?

This population-based register study examined if factors during the fetal and neonatal period influence the risk for the child to develop bronchial asthma (asthma). From the Swedish Hospital Discharge Register we identified children, born between 1987 and 1999, who had been hospitalized for asthma up to 2001. Thus, the outcome measure contains only hospitalized cases, not all children with asthma. Children younger than 2 yr at admission were excluded because of the uncertainty about the diagnosis of asthma in younger children. The remaining 14,803 children were compared with all children born the same years, recorded in the Swedish Medical Birth Registry, for information on pre- and perinatal characteristics. Odds ratios (ORs) were calculated with Mantel-Haenszel technique and 95% confidence intervals (CIs) with Miettinen's test-based method. The presence of various maternal and neonatal confounders were identified and adjusted for in the analyses. The association between some known factors and childhood asthma were confirmed: young maternal age, maternal smoking, period of unwanted childlessness, low maternal level of education, maternal diabetes, preterm birth, low birth weight, small-for-gestational age, caesarean section, and instrumental vaginal delivery. A number of neonatal characteristics were shown to be independent risk factors: sepsis or pneumonia, neonatal respiratory problems and treatments, neonatal icterus, and/or neonatal phototherapy. The association with icterus and phototherapy remained after exclusion of cases showing other neonatal risk factors and after adjustment for maternal factors (OR 1.27, 95% CI: 1.08-1.50), and increased to 1.5 if the children had been hospitalized for asthma more than once. In conclusion, our results suggest an association between neonatal icterus and/or treatment with neonatal phototherapy and hospitalized childhood asthma. This association needs further exploration.

School performance in children with type 1 diabetes--a population-based register study

AIMS/HYPOTHESIS

We examined the school marks of diabetic children in Sweden at the time of leaving compulsory education. Marks were examined in comparison with non-diabetic children and with special regard to age at onset of diabetes.

SUBJECTS AND METHODS

The study involved 5,159 children who developed diabetes between 1 July 1977 and 1 July 2000, and 1,330,968 non-diabetic children. We linked the nationwide Swedish Childhood Diabetes Register to the Swedish School-Mark Register, which contains school marks for all children in Sweden at the time of leaving compulsory education (usually at 16 years old). Adjustment was made for potential confounders such as year of birth, maternal age, parity and educational level.

RESULTS

The mean of all numerical school marks for diabetic children was slightly but statistically significantly lower than those of the referent children (3.15 +/- 0.01 [mean + SD] vs 3.23, p < 0.001). The lowest mean score was among children with diabetes diagnosis before the age of 2 years (2.97 +/- 0.09 vs 3.08-3.17 in the older age groups, p = 0.10). When individual subjects were studied (sports, mathematics, English and Swedish), a more complex picture emerged. In four subjects (mathematics, English, Swedish and sports) the risk of a diabetic child not getting a school mark or not passing was increased; in sports and English the diabetic children had significantly reduced odds of getting a high mark.

CONCLUSIONS/INTERPRETATION

Despite a well-developed diabetes care system, we have not succeeded in preventing the disease from affecting school achievements. Among children with a young age at onset and therefore longer duration, the negative effects tend to be greater.

A functional polymorphism in the manganese superoxide dismutase gene and diabetic nephropathy

Oxidative stress has been suggested to contribute to the development of diabetic nephropathy. Manganese superoxide dismutase (MnSOD) protects the cells from oxidative damage by scavenging free radicals. The demand for antioxidants is increased by smoking, which could disturb the balance between antioxidants and radicals. The present study aimed to determine whether a valine/alanine polymorphism in MnSOD (V16A, rs4880), alone or in combination with smoking, can contribute to development of diabetic nephropathy in 1,510 Finnish and Swedish patients with type 1 diabetes. Overt diabetic nephropathy (n = 619) was defined as having an albumin excretion rate (AER) >200 microg/min or renal replacement therapy; incipient diabetic nephropathy was defined as having an AER of 20-200 microg/min (n = 336). The control subjects had diabetes duration of >or=20 years, without albuminuria (AER <20 microg/min) and without antihypertensive treatment (n = 555). In addition to male sex and elevated A1C, smoking was significantly associated with diabetic nephropathy (overt plus incipient), odds ratio (OR) 2.00 (95% CI 1.60-2.50). When controlling for age at onset, diabetes duration, A1C, smoking, and sex, the Val/Val genotype was associated with an increase in risk of diabetic nephropathy (1.32 [1.00-1.74], P = 0.049). When evaluating the combined effect of genotype and smoking, we used logistic regression with stratification according to smoking status and genotype. The high-risk group (ever smoking plus Val/Val genotype) had 2.52 times increased risk of diabetic nephropathy (95% CI 1.73-3.69) compared with the low-risk group, but no departure from additivity was found. Our results indicate that smoking and homozygosity for the MnSOD Val allele is associated with an increased risk of diabetic nephropathy, which supports the hypothesis that oxidative stress contributes to the development of diabetic nephropathy.

Genetic association analysis of the adiponectin polymorphisms in type 1 diabetes with and without diabetic nephropathy

OBJECTIVE

Adiponectin [adipocyte C1q and collagen domain containing (ACDC)] is the most abundant adipose-specific protein. It is beneficial in that it improves insulin sensitivity and mitigates vascular damage, in addition to the possibility of it having anti-inflammatory properties. Clinical evidences demonstrate that serum adiponectin concentrations are increased in patients with type 1 diabetes (T1D) as well as in patients with microvascular complications. However, the genetic influence of the ACDC gene in T1D and diabetic microvascular complications is still unclear. The present study aims to evaluate the association of the ACDC genetic variation in T1D and diabetic nephropathy (DN).

MATERIALS AND METHODS

Ten single nucleotide polymorphisms (SNPs) of the ACDC gene were genotyped in 432 T1D patients (of which, 196 had DN) and 187 nondiabetic control subjects, who were all Swedish Caucasians, by using dynamic allele specific hybridization.

RESULTS

Single-marker association analysis demonstrated that SNPs +45G15G(T/G) and +276(G/T) were strongly associated with T1D [P=.002, OR=1.855 (1.266-2.717) and P=.001, OR=1.694 (1.337-2.147)]. Further analysis for haplotypes of these two SNPs indicated that one of the common haplotype (T_G) was strongly associated with T1D [P<.001, OR=1.769 (1.430-2.188)]. However, there was no significant difference in the allele frequencies of these two SNPs between the groups of T1D patients with nephropathy and the patients without nephropathy.

CONCLUSIONS

The present study thus suggests that SNPs +45G15G(T/G) and +276(G/T) in the ACDC gene are associated with T1D but not with DN among Swedish Caucasians.

Genetic influences of the intercellular adhesion molecule 1 (ICAM-1) gene polymorphisms in development of Type 1 diabetes and diabetic nephropathy

AIM

The intercellular adhesion molecule-1 (ICAM-1) gene is located on chromosome 19p13, which is linked to Type 1 diabetes (T1D). ICAM-1 expression is related to development of T1D and diabetic nephropathy. The present study aims to evaluate the genetic influence of ICAM-1 gene polymorphisms on the development of T1D and diabetic nephropathy.

METHODS

Five valid single nucleotide polymorphisms (SNPs) were genotyped in 432 T1D patients (196 patients had diabetic nephropathy) and 187 non-diabetic control subjects by using dynamic allele-specific hybridization (DASH) and pyrosequencing.

RESULTS

SNPs rs281432(C/G) and rs5498 E469K(A/G) had high heterozygous indexes. They were significantly associated with T1D [P = 0.026, OR = 1.644 (95% CI 1.138-2.376) and P < 0.001, OR = 2.456 (1.588-3.8)]. Frequencies of the C allele in SNP rs281432(C/G) and the A allele in SNP rs5498 E469K(A/G) increased stepwise from non-diabetic control subjects to T1D patients without diabetic nephropathy and T1D patients with diabetic nephropathy. Further analysis for these two SNPs indicated that T1D patients had increased frequency of the common haplotype C-A, in comparison with non-diabetic control subjects (38.1 vs. 32.1%, P = 0.035).

CONCLUSION

The present study provided evidence that SNPs rs281432(C/G) and rs5498 E469K(A/G) in the ICAM-1 gene confer susceptibility to the development of T1D and might also be associated with diabetic nephropathy in Swedish Caucasians.

Fetal and perinatal risk factors for inflammatory bowel disease

AIM

To study the influence of specific factors and events during pregnancy and the perinatal period on the risk of children developing inflammatory bowel disease.

METHODS

Population-based national register study. Linkage between the Swedish Medical Birth Register and the Swedish Hospital Discharge Register during the period 1987 to 2000 identified 455 singleton infants who later developed inflammatory bowel disease. Data for these children were compared with data for all children born in Sweden during the same period.

RESULTS

Smoking during early pregnancy reduced the risk of inflammatory bowel disease (odds ratio (OR) 0.71, 95% CI 0.55-0.91). For ulcerative colitis the odds ratio was 0.70 (95% CI 0.56-0.86), and for Crohn's disease 0.73 (95% CI 0.58-0.94). Infections during the neonatal period seemed to increase the risk of inflammatory bowel disease (OR 17.6, 95% CI 3.6-51.6), but the number of observed events was small. The other factors examined did not influence the risk of inflammatory bowel disease.

CONCLUSION

Maternal smoking during early pregnancy reduces the risk for the child to be hospitalized with a diagnosis of inflammatory bowel disease. Severe neonatal infections may increase the risk. Thus, some exposures during the fetal and neonatal period seem to affect the risk of inflammatory bowel disease later in life.

Age at onset of childhood-onset type 1 diabetes and the development of end-stage renal disease: a nationwide population-based study

OBJECTIVE

To analyze the impact of age at onset on the development of end-stage renal disease (ESRD) due to diabetic nephropathy in a nationwide population-based cohort with childhood-onset type 1 diabetes.

RESEARCH DESIGN AND METHODS

A record linkage between two nationwide registers, the Swedish Childhood Diabetes Registry, including 12,032 cases with childhood-onset diabetes, and the Swedish Registry for Active Treatment of Uraemia was performed. Log-rank test was used to test differences between cumulative risk curves of developing ESRD due to diabetic nephropathy in three different strata of age at onset (0-4, 5-9, and 10-14 years).

RESULTS

At a maximum follow-up of 27 years, 33 patients had developed ESRD due to diabetic nephropathy and all had a diabetes duration >15 years. In total, 4,414 patients had diabetes duration >15 years, and thus the risk in this cohort to develop ESRD was 33 of 4,414 (0.7%). A significant difference in risk of developing ESRD was found between the youngest (0-4 years) and the two older (5-9 and 10-14 years) age-at-onset strata (P = 0.03 and P = 0.001, respectively). A significant difference in the risk of developing ESRD was also found between children with prepubertal (0-4 and 5-9 years, n = 2,424) and pubertal (10-14 years, n = 2000) onset of diabetes (P = 0.002). No patient with onset of diabetes before 5 years of age had developed ESRD.

CONCLUSIONS

With a median duration of 21 years in this population-based Swedish cohort with childhood-onset diabetes, <1% of the patients had developed ESRD due to diabetic nephropathy, and a prepubertal onset of diabetes seems to prolong the time to development of ESRD.

Glu298Asp and NOS4ab polymorphisms in diabetic nephropathy

BACKGROUND AND AIMS

The risk of diabetic nephropathy (DN) increases with increase in intraglomerular pressure, which may partly be regulated by nitric oxide (NO). NO-production can be affected by polymorphisms in the endothelial NO-synthase gene (NOS3), hyperglycaemia and smoking. We therefore studied association between DN and two polymorphisms in NOS3, Glu298Asp and NOS4ab, in Caucasian type 1 diabetes (T1D) patients.

PATIENTS AND METHODS

A total of 1510 Finnish and Swedish T1D patients were included in a cross-sectional case-control study. Incipient DN was defined as an albumin excretion rate (AER) of 20-200 microg/min (n = 336). Overt DN = AER>200 microg/min or renal replacement therapy (n = 619). All patients with DN were considered as cases. The controls were T1D patients with diabetes duration 20 years, AER<20 microg/min and without antihypertensive treatment (n = 555). The genetic markers studied were a 27 bp repeat (NOS4ab) and Glu298Asp (rs1799983).

RESULTS

Age at onset of diabetes, male sex, duration of diabetes, HbA1c, blood pressure and smoking were assessed as possible confounders in the logistic regression analysis, which showed that homozygosity for the Glu-allele of the Glu298Asp-polymorphism was independently associated with increased risk of DN (OR = 1.46; 95% CI = 1.12-1.91). The variables smoking (OR = 2.13; 95% CI = 1.63-2.78), male sex (OR = 1.61; 95% CI = 1.23-2.10), HbA1c (OR per % increase above upper limit of the normal reference range = 1.02; 95% CI = 1.02-1.03), systolic (OR = 1.05; 95% CI = 1.04-1.06) and diastolic blood pressure (OR = 1.04; 95% CI = 1.02-1.05) also significantly and independently increased the risk of DN when taking age at diabetes onset and diabetes duration into account. The NOS4 a-allele was not associated with DN.

CONCLUSIONS

The Glu/Glu-genotype of the NOS3 Glu298Asp polymorphism may increase the risk of developing DN independently of other known risk factors.

Can we slow the rising incidence of childhood-onset autoimmune diabetes? The overload hypothesis

Overload of the beta cell, mediated by a variety of mechanisms, may sensitise it to immune damage and apoptosis, and thus accelerate ongoing autoimmune processes leading to its destruction. Environmental risk determinants that may exert such overload effects include insulin resistance due to excess fat cell accumulation, and increased insulin requirement due to a high growth rate, physical stress (infection, inflammation) or psychological stress. The increasing incidence of childhood diabetes, and the shift to younger age at onset, is unlikely to be driven by environmental risk factors that have been associated with initiation of autoimmunity, e.g. virus infections or early infant feeding. Risk factors that may accelerate beta cell destruction have shown a steady increase in the population, and are more plausible causes of such a pattern of change. Child growth, weight and birthweight are well-established estimates of community wealth and increase in most countries of Europe. Overfeeding of children early in life leads to both accelerated growth and weight, and even a moderate excess of child growth, not necessarily associated with obesity, is associated with risk of type 1 diabetes. New, safe and effective immune-modulating drugs for possible arrest of the autoimmune process may become available in time, but in the interim these accelerating factors may be targeted. Public health programmes for pregnant mothers and young families, aiming at changing overfeeding and the sedentary lifestyle of the children would be preferable to other alternatives. Interventions such as these would be safe and could potentially influence future risks of type 1 and type 2 diabetes and other major threats to adult health.

Mortality in childhood-onset type 1 diabetes: a population-based study

OBJECTIVE

To describe the age- and sex-specific mortality in a cohort of young type 1 diabetic patients and to analyze the causes of death with special focus on suicide, accidents, and unexplained deaths.

RESEARCH DESIGN AND METHODS

A population-based incident childhood diabetes register, covering onset cases since 1 July 1977, was linked to the Swedish Cause of Death Register up to 31 December 2000. The official Swedish population register was used to calculate age- and sex-standardized mortality rates (SMRs), excluding neonatal deaths. To analyze excess risks for specific diagnoses, case subjects were compared with five nondiabetic control subjects, matched by age, sex, and year of death. Death certificates were collected for all case and control subjects. For case subjects with an unclear diagnosis, hospital records and/or forensic autopsy reports were obtained.

RESULTS

Mean age- and sex-SMR was 2.15 (95% CI 1.70-2.68) and tended to be higher among females (2.65 vs. 1.93, P = 0.045). Mean age at death was 15.2 years (range 1.2-27.3) and mean duration 8.2 years (0-20.7). Twenty-three deaths were clearly related to diabetes; 20 died of diabetic ketoacidosis. Only two case subjects died with late diabetes complications (acute coronary infarction). Thirty-three case subjects died with a diagnosis not directly related to diabetes; 7 of them committed suicide, and 14 died from accidents. There was no significant difference in traffic accidents (odds ratio 1.02 [95% CI 0.40-2.37]). Obvious suicide tended to be increased but not statistically significantly so (1.55 [0.54-3.89]). Seventeen diabetic case subjects were found deceased in bed without any cause of death found at forensic autopsy. Only two of the control subjects died of similar unexplained deaths.

CONCLUSIONS

In a well-developed health care system, there is still a significant excess mortality in young type 1 diabetic patients. We confirm a very large proportion of unexplained deaths in bed, which should be further studied. There is no clear excess death rate caused by suicide or traffic accidents among young diabetic subjects.

Time trend of childhood type 1 diabetes incidence in Lithuania and Sweden, 1983-2000

AIM

To compare the time trend of childhood type 1 diabetes over an 18-y period in Lithuania and Sweden--countries with different incidence levels and different socio-economic conditions.

METHODS

Percent average incidence change per year between 1983 and 2000, based on 8031 Swedish and 1100 Lithuanian cases in the age group 0-14 y, was calculated using Poisson regression.

RESULTS

Average age- and sex-standardized incidence/100 000/y was 28.9 (95% CI: 28.2-29.5) in Sweden and 7.5 (95% CI: 7.1-8.0) in Lithuania. Between 1983 and 2000, the average increase per year was 2.2% in Sweden (95% CI: 1.7-2.6) and 2.3% in Lithuania (95% CI: 1.1-3.5), but the latter trend depended on an increase during the last few years of the period, and only for girls. In Sweden, incidence increased significantly in all age groups, but more so in the younger groups (3.0%, 2.2% and 1.7% per year in 0-4, 5-9 and 10-14-y age groups, respectively), while in Lithuania a significant increase was found only in the 10-14-y age group (3.0%). In Sweden, a trend towards a younger age at diagnosis was indicated for both boys and girls when comparing 1983-1991 and 1992-2000, whereas in Lithuania, the changes in age distribution over time were small, with an opposite tendency for boys.

CONCLUSION

Incidence variability over time differed considerably in the two countries in the region of the Baltic Sea, suggesting a complex effect of environmental risk factors, some of which may be associated with wealth and socio-economic conditions.

Diet, growth, and the risk for type 1 diabetes in childhood: a matched case-referent study

OBJECTIVE

To study the association between type 1 diabetes risk and previous intake of energy, accounting for body size and previous intake of nutrients and foods, accounting for the energy intake.

RESEARCH DESIGN AND METHODS

We conducted an incident population-based case-referent study in Stockholm, Sweden, including 99 of 100 eligible 7- to 14-year-old diabetic children and 180 of 200 age-, sex-, and area-matched referent children identified through the Swedish population register. Average daily energy and nutrient intake 1 year before diabetes diagnosis/interview was estimated using the food frequency questionnaire with assessment of consumed food amounts. Mean SD scores of growth measurements taken during the last 4 years before the diagnosis were used. Odds ratios (ORs) were calculated by conditional logistic regression.

RESULTS

Average intake of energy, carbohydrate, fat, and protein was significantly higher among the case subjects as well as mean weight-for-age SD score. Higher energy intake and weight-for-age were both associated with increased diabetes risk after adjustment for each other: OR (95% CI) for medium and high levels of energy intake were 1.33 (0.52-3.42) and 5.23 (1.67-16.38), respectively, and for weight-for-age were 3.20 (1.30-7.88) and 3.09 (1.16-8.22), respectively. High intake of carbohydrates, especially disaccharides and sucrose, increased diabetes risk.

CONCLUSIONS

Higher energy intake and larger body size were independently associated with increased diabetes risk. Of the different nutrients, higher intake of carbohydrates, particularly disaccharides and sucrose, increased the risk. Lifestyle habits leading to higher energy intake and more rapid growth in childhood may contribute to the increase of childhood-onset type 1 diabetes by different mechanisms.

Early glycemic control, age at onset, and development of microvascular complications in childhood-onset type 1 diabetes: a population-based study in northern Sweden

OBJECTIVE

The aim of this work was to study the impact of glycemic control (HbA(1c)) early in disease and age at onset on the occurrence of incipient diabetic nephropathy (MA) and background retinopathy (RP) in childhood-onset type 1 diabetes.

RESEARCH DESIGN AND METHODS

All children, diagnosed at 0-14 years in a geographically defined area in northern Sweden between 1981 and 1992, were identified using the Swedish Childhood Diabetes Registry. From 1981, a nationwide childhood diabetes care program was implemented recommending intensified insulin treatment. HbA(1c) and urinary albumin excretion were analyzed, and fundus photography was performed regularly. Retrospective data on all 94 patients were retrieved from medical records and laboratory reports.

RESULTS

During the follow-up period, with a mean duration of 12 +/- 4 years (range 5-19), 17 patients (18%) developed MA, 45 patients (48%) developed RP, and 52% had either or both complications. A Cox proportional hazard regression, modeling duration to occurrence of MA or RP, showed that glycemic control (reflected by mean HbA(1c)) during the follow-up was significantly associated with both MA and RP when adjusted for sex, birth weight, age at onset, and tobacco use as potential confounders. Mean HbA(1c) during the first 5 years of diabetes was a near-significant determinant for development of MA (hazard ratio 1.41, P = 0.083) and a significant determinant of RP (1.32, P = 0.036). The age at onset of diabetes significantly influenced the risk of developing RP (1.11, P = 0.021). Thus, in a Kaplan-Meier analysis, onset of diabetes before the age of 5 years, compared with the age-groups 5-11 and >11 years, showed a longer time to occurrence of RP (P = 0.015), but no clear tendency was seen for MA, perhaps due to lower statistical power.

CONCLUSIONS

Despite modern insulin treatment, >50% of patients with childhood-onset type 1 diabetes developed detectable diabetes complications after approximately 12 years of diabetes. Inadequate glycemic control, also during the first 5 years of diabetes, seems to accelerate time to occurrence, whereas a young age at onset of diabetes seems to prolong the time to development of microvascular complications.

Acute intermittent porphyria in childhood: a population-based study

AIM

To establish age-adjusted reference intervals of urinary delta-aminolaevulinic acid (U-ALA) and porphobilinogen (U-PBG) in children, and to analyse the frequency and type of clinical manifestations of acute intermittent porphyria (AIP) in childhood.

METHODS

Concentrations of U-ALA and U-PBG in healthy children aged 3-16y were analysed. In a population-based study in northern Sweden of 61 children aged < 18 y with DNA-verified AIP, the clinical manifestations of AIP in childhood were analysed prospectively (up to 2.5 y). Initially the children underwent a standardized investigation (anamnesis, physical examination, laboratory tests). Instructions were issued to keep a structured diary and to provide urine samples for ALA and PBG analyses in all situations of suspected AIP attacks (prospectively).

RESULTS

Reference intervals for U-ALA and U-PBG showed age-group variations in children. Baseline levels of U-ALA and U-PBG are increased in gene carriers, one-quarter of them exceeding the 90th percentile of age- and gender-matched controls. Baseline levels did not distinguish symptomatic from non-symptomatic children in a short-term perspective. Clinical evidence of AIP attacks was found in 10% of child AIP gene carriers; in all cases the first attack occurred before the age of 15 y.

CONCLUSION

AIP symptoms in children may be vague and of short duration and U-ALA and U-PBG levels are often elevated only slightly or not at all; thus, symptoms and signs may differ from those in adults. Children of AIP gene carriers should be DNA tested, followed up and carefully instructed on preventive measures to avoid developing manifest AIP.