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

AIMS/HYPOTHESIS

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

METHODS

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

RESULTS

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

CONCLUSIONS/INTERPRETATION

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

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.

Blood pressure levels in 7 to 14-year-old Belgrade children

The objective of the work was to study blood pressure and some anthropometric characteristics in children. The study design included the prevalence study at Belgrade, Serbia and Montenegro. The study comprised 1651 subjects (809 boys and 842 girls) aged 7-14 years, that is, 2.6% of all relevant population. The average levels of systolic and diastolic blood pressures (SBP and DBP) were 113.4/70.3 mmHg in boys and 114.6/71.1 mmHg in girls. High SBP was present in 4.7% of boys and in 5.3% of girls. High DBP was found in 5.6% of boys and in 4.8% of girls. According to multivariate regression analysis, in boys SBP and DBP were significantly associated with age, body mass index (BMI) and subscapular skinfold, SBP was also associated with body weight, and DBP with triceps skinfold. In girls, SBP was significantly related to BMI, suprailiac skinfold and body height, and DBP was significantly associated with BMI, suprailiac and subscapular skinfolds. The results of the present study support the opinion that BMI is a significant predictor of blood pressure in children and point out to suprailiac skinfold in girls as a possible predictor of blood pressure.

Family history and risk of type 1 diabetes mellitus

The aim of the study was to evaluate association of type 1 diabetes in children and adolescents with positive family history of type 1 diabetes, type 2 diabetes, and thyroid, adrenal, rheumatic, allergic, celiac and some other diseases. A case-control study was conducted in Belgrade. The case group comprised 105 subjects < or = 16 years old who were for the first time hospitalized because of type 1 diabetes during the period 1994-1997. For each case, two controls were chosen among children and adolescents treated for skin diseases. Cases and controls were individually matched by age (+/- one year), sex and place of residence (all were from Belgrade). In the statistical analyses we used chi(2)-test, Fisher's exact test and univariate and multivariate logistic regressions. According to multivariate logistic regression analysis, risk of type 1 diabetes was significantly associated with a positive family history for type 1 diabetes (OR = 4.04; 95% CI, 2.31-7.07), allergic diseases (OR = 3.32; 95% CI, 1.63-6.76), celiac and Crohn's diseases (OR = 11.02; 95% CI, 1.14-106.89) and other diseases (thrombocytopenia, alopecia areata, psoriasis, chronic uveitis and pernicious anemia; OR = 3.63; 95% CI, 1.05-12.48).

[Trends in mortality in Serbia, excluding the provinces, 1973-1994]

The war and break up of former Yugoslavia began in 1991. In May 1992 the United Nations imposed economic sanctions on Serbia and Montenegro which were suspended only in November 1995. The purpose of this study was to assess the effects of the war and UN sanctions on health of the population of Serbia without the provinces of Vojvodina and Kosovo. The period 1973-1994 was studied. Mortality data were derived from unpublished and published materials of the Federal Institute of Statistics [1]. Refugees, who, because of civil war, came to Serbia and Montenegro from other parts of former Yugoslavia, were not counted as a part of the population when mortality rates were calculated. Mortality rates were standardized directly using the "European population" as the standard [2]. The least square method was used to fit mortality rates to different trend curves. Linear trend was used whenever it significantly (p < 0.05) demonstrated the existing mortality rates. To measure the possible effect of the war and sanctions (WAS) on mortality between 1991 and 1994, dummy variable (variable WAS) consisting of 0's and 1's was made to signify the passage from the period before and the period after the beginning of the war and sanctions [3]. Over the period 1991-1994, characterized by the war and UN sanctions, in women aged 25-34, 35-44 and 75-84, total mortality was significantly higher than expected on the basis of the trend for the preceding period (p = 0.006, p = 0.000 and p = 0.015 respectively). The opposite effect was found in the age group 85+ (p = 0.012)/Table 2. Of major causes of death, in age group 25-34, mortality from endocrine diseases increased more rapidly in both sexes (p = 0.000) and mortality from urogenital diseases in women decreased more slowly than expected (p = 0.006). On the other hand, in age group 85+ mortality was significantly lower for cardiovascular diseases in both sexes (p = 0.035 and p = 0.006), for respiratory diseases in men (p = 0.011) and for neoplasms in women (p = 0.006)/Table 4. In addition, in the years 1991 and 1992 the increase in mortality from injuries and poisoning was evident in men aged 15-24, 25-34 and 85+ years (Graph 5). Our results show that over the period 1991-1994 changes in mortality were present in some age groups and were caused by certain groups of diseases. In men, besides mortality of infectious disease which decreased more slowly during 1991-1993 than expected, [4], the main departures were found in the mortality from injuries and poisoning and in mortality from endocrine diseases. The excess of death due to injuries and poisoning in the age group 15-34 can be explained as a direct consequence of the war. There were no military operations on the territory of Serbia, but young men from Serbia were nevertheless engaged in the war in other republics of former Yugoslavia. The outstanding increase in mortality caused by injuries and poisoning in men aged 85+ has two explanations. The first is the fact that suicide rate which was on an average of 86 per 100,000 over the period 1984-1990 rose to 140 per 100,000 during the period 1991-1993. In the year 1994 it fell to 92 per 100,000. Since there were no great differences in percent distribution of suicides among all deaths caused by injuries and poisoning in the two periods (27% in 1984-1990 and 20% in 1991-1993), it is clear that the rise of suicidal rate cannot be the only explanation for increased mortality from injuries and poisoning. In a situation when medical services were badly overextended (lack of medical equipment and proper maintenance of the existing equipment, lack of drugs and other medical inputs, a large number of wounded coming from Bosnia as well as numerous refugees) [5, 6], priority had to be given to younger age groups. Higher mortality due to endocrine diseases in men and women aged 25-34 years and higher mortality due to urogenital diseases in women of the same ages can be most probably attributed to poor medical supplies. Although formally excluded from the international economic blockade medical supplies were in practice badly affected by the fact that the dinar was rendered almost worthless and the Ministry of Health could no longer pay the medical inputs. In addition, bureaucratic hurdles of getting clearance from the UN added months of delay and made foreign companies unwilling to trade [5, 7]. The supply and distribution of drugs within the country was also irregular because communication lines were cut and local companies were not prepared to risk distributing drugs that nobody could pay for [7]. Higher than expected mortality in women aged 25-44 over the period 1991-1994 could be probably explained by their higher vulnerability (period of fertility) and the fact that the main burden of family survival was on them, so they had no time to think and to take care of their health. (ABSTRACT TRUNCATED)

Incidence of gonorrhea in Belgrade, 1988-1994

The incidence of gonorrhea in Belgrade decreased 55.5% from 1988 to 1994, but a decreasing trend of gonorrhea incidence actually started many years before. In all age groups gonorrhea incidence was higher in men than women, and the male/female ratio increased with age. The incidence was highest in men and women 20-29 years old. In both sexes the lowest incidence was below 15 years of age and in persons 50 or more years of age. In men, service and industrial workers were the most frequently affected by gonorrhea. In women the disease was commonest among unemployed persons and among workers of the service and industrial sectors. In both sexes gonorrhea infection was commonest in populations who had never married, and in the divorced population.

[Demographic characteristics of patients with gonorrhea in the Belgrade population 1988-1994]

The basic demographic characteristics of the patients with gonorrhea in Belgrade population in the period 1988-1994 were analysed on the basis of the reports of gonorrhea newly diseased to the City Institute for Skin and Venereal Diseases. The decrease of gonorrhea incidence was observed in the period 1988-1992, and the lowest value of 21.2 cases per 100,000 inhabitants was noted in 1992. Gonorrhea incidence increased for 23.8% compared to 1992. The disease is more frequently found in males, aged 20-29, industrial and service workers and unemployed. Unmarried persons had the highest incidence rate of gonorrhea.

Risk factors for gonorrhoea: case-control study

OBJECTIVE

To define risk factors for gonococcal infection.

METHODS

A case-control study comparing 200 gonorrhoea cases with 400 patients with non-gonococcal genitourinary infections and 400 patients with various skin diseases, all of them attending City Department for Skin and Venereal Diseases In Belgrade (Yugoslavia) from October 1993 to December 1994.

RESULTS

According to multivariate logistic regression analysis the following factors were significantly related to gonorrhoea in men: education level, sexual contact same day as meeting, condom use, history of prior gonorrhoea, and casual and/or new sex partner in the past month. Age, sexual contact same day as meeting, number of partners in the past year, and frequency of sexual intercourse in the past month were independently, significantly related to gonorrhoea in women. Also, in females, gonorrhoea was significantly more frequent in industrial workers and supported people.

CONCLUSION

Since sexual behaviour, low education level, younger ages, and low socioeconomic status were found to be related to gonococcal infection, health education at early age seems to be the most appropriate means of altering high risk behaviour.

[The effect of cigarette smoking during pregnancy on fetal growth]

The association between maternal smoking and poor pregnancy outcome, which is well established in medical literature, has been confirmed during the study conducted in one of Belgrade hospitals. The study comprised 1011 women who gave birth to a live born baby between June 1992 and March 1993 (infants with malformations were excluded). The women were interviewed by one person during the first three days after delivery. Data were collected on smoking habits during the first, second and third trimester of pregnancy, and on potential confounders including age, education, marital status, obstetric history, height, weight before pregnancy, weight gain during pregnancy, history about diseases before and during pregnancy, housekeeping and occupational activities, data about delivery and data about alcohol consumption. By the use of factor analysis infants characteristics, taken from medical histories, were classified in two groups: I group-birth weight, birth length, head circumference and chest circumference; II group-apgar score after one and after five minutes. The rough relation of smoking to the outcome was examined first. Adjustment was made for the potential confounders by the use of multiple regression analysis. Variables associated with both smoking and birth weight or apgar score after one minute (i.e. maternal height and weight) were considered as potential confounders. Infant sex, gestational age and parity were also included as possible confounders due to their strong link with birth weight and apgar. In the sample 42% of women were smokers, and 98% of them smoked filter cigarettes. In the group of smokers 312 smoked throughout pregnancy and 111 were inconsistent smokers (those who smoked during one or two trimesters only). According to smoking habits, mothers were divided into three groups: nonsmokers, those who smoked 1-9 cigarettes per day and those who smoked 10 or more cigarettes per day (Table 1). There was a strong relationship with significant linear trend between smoking and all observed birth outcomes except apgar score (Table 2). Significant reductions in birth weight (by 205 g), birth length (by 1.28 cm), head circumference (by 0.38 cm) and chest circumference (by 0.66 cm) were found to be associated with an average daily smoking of 10 or more cigarettes after adjustment was made for potential confounders. Even a smaller number of cigarettes affected foetal growth. Infants born by mothers who throughout pregnancy smoked 1-9 cigarettes per day (mean 4.07, range 1-8) weighted significantly less (by 89 g) and had head circumference significantly smaller (by 0.23 cm) in comparison with infants born by mothers nonsmokers. Inconsistent smoking during pregnancy had no significant effect on foetal growth with the exception of smaller birth length (by 2.30 cm; p = 0.002) in infants born by mothers who smoked during the second and third trimester. It is possible that the relatively small number of women inconsistent smokers had a bearing on the results. According to the results obtained it seems that either there is no threshold for the effect of smoking on foetal growth, or it is very low. Nevertheless, since the effect of smoking is weaker if the number of cigarettes smoked is smaller it is reasonable to assume that the reduction in the number of cigarettes smoked in pregnancy would serve as prevention irrespective whether the threshold existed or not.

[Epidemiologic characteristics of malignant tumors of the digestive tract in Serbia 1969-1990]

The epidemiological situation of the chosen malignant tumors of digestive tract for the period 1969 - 1990, was analyzed in Serbia without autonomous provinces, based on the data of mortality rate. During this observed 22-year period the average standardized mortality rate (%000) was lowest for the oesophageal cancer (men - 2.2; women - 0.6) and gall bladder cancer (1:1.8) and highest for the stomach cancer (14.3:7.1). Men in relation to women died more of oesophageal cancer (3.7 times), stomach (2 times), colon (1.2 times), rectum (1.4 times) and pancreas (1.7 times). In both male and female population the highest average specific mortality rates were observed for persons over the age of 75 for all observed malignancies of digestive system. The standardized mortality rates for both sexes for the period 1969-1990 demonstrated the trend of increase for the cancers of oesophagus, colon, rectum, gall bladder, and pancreas, and the decrease for the stomach cancer.

[Epidemiologic-anamnestic study of stomach cancer in relation to nutrition]

Correlation between the disease and nutritional habits was evaluated in this epidemiologic-anamnestic study. It included 80 patients with the confirmed diagnosis of stomach cancer and the same number of controls selected from five hospitals in Belgrade. Both groups were matched by the sex, age and living place. McNemar's test was used for testing differences in exposure to the hypothetic factors. Based on the analysis of various food intake frequency it could be concluded that nutrition of patients with stomach cancer was, in comparison with the one taken by the control group, poorer in animal proteins, vegetables and citrus fruits, and rich in cereals processed in the form of various pastas and sweets, delicatessen, canned food as well as fruit rich in unsaturated fatty acids (nuts).

[Effect of a reducing diet and physical activity in obese individuals with arterial hypertension]

The effects of reducing diet of 4.4 MJ with reduced daily sodium chloride intake and physical activity (walking and floor exercise) in 90 patients of the Counseling office for Dietetics (23 males and 67 females) with excessive obesity and arterial hypertension (AH) were examined. Although both groups of patients were of the similar nutritional status, rate of the body mass loss during the diet was significantly higher in males (p < 0.05). At the end of the diet therapy, beside reduced body mass, significantly lower average systolic and diastolic pressure (p < 0.01) was observed in both sexes. Correlation analysis showed significant positive correlation between the weight loss rate and reduced diastolic pressure (p < 0.05) only in females.

Trends in cancer mortality of the digestive tract in Belgrade, Yugoslavia, 1975-1989

During the period of 1975-1989, in the Belgrade population increasing mortality trends were established for colon and rectal cancer, cancer of the pancreas and gallbladder and bile ducts cancer, for both sexes, and for esophageal cancer in males. Stomach and liver cancer mortality decreased in females. In males, stomach cancer mortality after a prolonged steady decrease suddenly rose in the years 1988 and 1989. Mortality rates series for esophageal cancer in females and for liver cancer in males did not fit any usual trend function.

[Incidence of insulin-dependent diabetes mellitus in the population of Belgrade, 0-19 years of age, from 1990 to 1992]

The data on insulin-dependent diabetes mellitus incidence in the population of Belgrade from the age of 0 to 19 have been gathered retrogradely. Two sources of data were used: hospital documentation and Registers for diabetics. During the period 1990-1992, 99 persons got sick of insulin-dependent diabetes while possibility includes 95.05% newly sick. The average rates of incidence, standardized according to the age distribution in the world population were 9.7/10000 (95% the confidence interval 6.5-14.0) for the age from 0-14 and 8.4 (95% confidence interval 5.8-11.8) for the age 0-19. The rates were highest from the age of 5-9 and 10 to 14. The relation of rates between sexes approximately equals one, but according to the age, differences between sexes were expressed. In females the highest rates of incidence were recorded at the age of 5, 7 and 8 and in males at the age of 7, 11 and 12. According to the results of this investigation, Belgrade belongs to areas with averagely high rates of incidence concerning insulin-dependent diabetes.

[Evaluation of the association of cancer of the esophagus, stomach and colon with habits of patients]

The demographic characteristics (sex, age, occupation) of patients with cancers of the esophagus, stomach and colon are reported and the importance of smoking and consumption of alcohol and coffee in development of the disease have been evaluated. The etiologic studies comprised 366 patients (100 with esophageal cancer, 80 with stomach cancer and 186 with colon cancer) and 366 controls. NcNamary test was used in differentiation of the rates of the matched samples. The most significant relationship of smoking and alcohol consumption was found for esophageal cancer (RR = 4.4; RR = 9.0, p 0.0001), somewhat less for stomach cancer (RR = 2.0, p 0.05; RR = 1.5) and least for colon cancer (RR = 0.9, RR = 1.1). Coffee consumption was most frequent in patients with cancer of the esophagus and colon while negative correlation was obtained for stomach cancer.