Detecting potential outliers in longitudinal data with time-dependent covariates.

BACKGROUND: Outliers can influence regression model parameters and change the direction of the estimated effect, over-estimating or under-estimating the strength of the association between a response variable and an exposure of interest. Identifying visit-level outliers from longitudinal data with continuous time-dependent covariates is important when the distribution of such variable is highly skewed. OBJECTIVES: The primary objective was to identify potential outliers at follow-up visits using interquartile range (IQR) statistic and assess their influence on estimated Cox regression parameters. METHODS: Study was motivated by a large TEDDY dietary longitudinal and time-to-event data with a continuous time-varying vitamin B12 intake as the exposure of interest and development of Islet Autoimmunity (IA) as the response variable. An IQR algorithm was applied to the TEDDY dataset to detect potential outliers at each visit. To assess the impact of detected outliers, data were analyzed using the extended time-dependent Cox model with robust sandwich estimator. Partial residual diagnostic plots were examined for highly influential outliers. RESULTS: Extreme vitamin B12 observations that were cases of IA had a stronger influence on the Cox regression model than non-cases. Identified outliers changed the direction of hazard ratios, standard errors, or the strength of association with the risk of developing IA. CONCLUSION: At the exploratory data analysis stage, the IQR algorithm can be used as a data quality control tool to identify potential outliers at the visit level, which can be further investigated.

Associations of dietary patterns between age 9 and 24 months with risk of celiac disease autoimmunity and celiac disease among children at increased risk.

BACKGROUND: Higher gluten intake in childhood is associated with increased incidence of celiac disease autoimmunity (CDA) and celiac disease. It remains to be studied whether different dietary patterns independent of gluten intake contribute to the incidence. OBJECTIVES: This study aimed to explore associations of dietary patterns by age 2 y with risk of CDA and celiac disease in genetically susceptible children. METHODS: Data was used from 6726 participants at genetic risk of type 1 diabetes and celiac disease enrolled in the observational cohort, The Environmental Determinants of Diabetes in the Young (TEDDY) study. Children were annually screened for tissue transglutaminase autoantibodies (tTGAs) from age 2 y. Principal component analysis extracted dietary patterns, based on intake of 27 food groups assessed by 3-d food records at age 9 to 24 mo. The primary outcome was CDA (i.e., persistently tTGA-positive in at least 2 consecutive samples), and the secondary outcome was celiac disease. During follow-up to mean age 11.0 (standard deviation 3.6) y, 1296 (19.3%) children developed CDA, and 529 (7.9%) were diagnosed with celiac disease. Associations of adherence to dietary patterns (per 5-unit increase) with the study outcomes were estimated by Cox regression models adjusted for risk factors including gluten intake. RESULTS: At age 9 mo, a dietary pattern higher in the food groups vegetable fats and milk was associated with reduced risk of CDA (hazard ratio [HR]: 0.88; 95% confidence interval [CI]: 0.79, 0.98; P = 0.02). At 24 mo, a dietary pattern higher in the food groups wheat, vegetable fats, and juices, and lower in milk, meat, and oats at age 24 mo was associated with increased risk of CDA (HR: 1.18; 95% CI: 1.05, 1.33; P < 0.001) and celiac disease (HR: 1.24; 95% CI: 1.03, 1.50; P = 0.03). CONCLUSIONS: Dietary patterns in early childhood are associated with risk of CDA and celiac disease in genetically predisposed children, independent of gluten intake.

Factors assessed in the first year of a longitudinal study predict subsequent study visit compliance: the TEDDY study.

BACKGROUND: Compliance with a study protocol is central to meeting its research goals. In longitudinal research studies, data loss due to missed visits limit statistical power and introduce bias. The Environmental Determinants of Diabetes in the Young (TEDDY) study is a longitudinal multinational (US, Finland, Germany, and Sweden) investigation of children at risk for type 1 diabetes (T1D) that seeks to identify the environmental triggers of islet autoimmunity and T1D. The purpose of the current study was to identify sociodemographic variables and maternal characteristics assessed in the first year of TEDDY that were associated with study visit compliance in the subsequent 3 years. METHODS: Sociodemographic variables, maternal life-style behaviors, post-partum depression, maternal reactions to the child's T1D risk, and study-related variables were collected at child-age 6 months and 15 months. Multiple linear regression was used to examine the association of these variables to study visit compliance in the subsequent 3 years. RESULTS: Study visit compliance was highest in Sweden (p > 0.001), in children who were their mother's first child (p > 0.001), and whose mothers were older (p > 0.001) and more satisfied with the TEDDY study (p > 0.001). Father participation was also associated with better study visit compliance (p > 0.001). In contrast, children whose mothers smoked (p > 0.001), suffered from post-partum depression (p = 0.034), and were more anxious about their child's T1D risk (p = 0.002), completed fewer visits. Father's study satisfaction was also associated with study visit compliance (p = 0.029); however, it was not significant in models that included maternal study satisfaction. CONCLUSIONS: Sociodemographic variables, maternal characteristics-including study satisfaction-and fathers' participation in the first year of a longitudinal study were associated with subsequent study visit compliance in a sample of children genetically at-risk for T1D followed for 4 years. This information can inform future strategies designed to improve study visit compliance in longitudinal pediatric studies. TRIAL REGISTRATION: NCT00279318, 06/09/2004.

Dietary Intake and Body Mass Index Influence the Risk of Islet Autoimmunity in Genetically At-Risk Children: A Mediation Analysis Using the TEDDY Cohort.

Background/Objective: Growth and obesity have been associated with increased risk of islet autoimmunity (IA) and progression to type 1 diabetes. We aimed to estimate the effect of energy-yielding macronutrient intake on the development of IA through BMI. Research Design and Methods: Genetically at-risk children (n = 5,084) in Finland, Germany, Sweden, and the USA, who were autoantibody negative at 2 years of age, were followed to the age of 8 years, with anthropometric measurements and 3-day food records collected biannually. Of these, 495 (9.7%) children developed IA. Mediation analysis for time-varying covariates (BMI z-score) and exposure (energy intake) was conducted. Cox proportional hazard method was used in sensitivity analysis. Results: We found an indirect effect of total energy intake (estimates: indirect effect 0.13 [0.05, 0.21]) and energy from protein (estimates: indirect effect 0.06 [0.02, 0.11]), fat (estimates: indirect effect 0.03 [0.01, 0.05]), and carbohydrates (estimates: indirect effect 0.02 [0.00, 0.04]) (kcal/day) on the development of IA. A direct effect was found for protein, expressed both as kcal/day (estimates: direct effect 1.09 [0.35, 1.56]) and energy percentage (estimates: direct effect 72.8 [3.0, 98.0]) and the development of GAD autoantibodies (GADA). In the sensitivity analysis, energy from protein (kcal/day) was associated with increased risk for GADA, hazard ratio 1.24 (95% CI: 1.09, 1.53), p = 0.042. Conclusions: This study confirms that higher total energy intake is associated with higher BMI, which leads to higher risk of the development of IA. A diet with larger proportion of energy from protein has a direct effect on the development of GADA.

HLA Genotype and Probiotics Modify the Association Between Timing of Solid Food Introduction and Islet Autoimmunity in the TEDDY Study.

OBJECTIVE: To study the interaction among HLA genotype, early probiotic exposure, and timing of complementary foods in relation to risk of islet autoimmunity (IA). RESEARCH DESIGN AND METHODS: The Environmental Determinants of Diabetes in the Young (TEDDY) study prospectively follows 8,676 children with increased genetic risk of type 1 diabetes. We used a Cox proportional hazards regression model adjusting for potential confounders to study early feeding and the risk of IA in a sample of 7,770 children. RESULTS: Any solid food introduced early (<6 months) was associated with increased risk of IA if the child had the HLA DR3/4 genotype and no probiotic exposure during the 1st year of life. Rice introduced at 4-5.9 months compared with later in the U.S. was associated with an increased risk of IA. CONCLUSIONS: Timing of solid food introduction, including rice, may be associated with IA in children with the HLA DR3/4 genotype not exposed to probiotics. The microbiome composition under these exposure combinations requires further study.

Interaction Between Dietary Iron Intake and Genetically Determined Iron Overload: Risk of Islet Autoimmunity and Progression to Type 1 Diabetes in the TEDDY Study.

OBJECTIVE: To examine whether iron intake and genetically determined iron overload interact in predisposing to the development of childhood islet autoimmunity (IA) and type 1 diabetes (T1D). RESEARCH DESIGN AND METHODS: In The Environmental Determinants of Diabetes in the Young (TEDDY) study, 7,770 genetically high-risk children were followed from birth until the development of IA and progression to T1D. Exposures included energy-adjusted iron intake in the first 3 years of life and a genetic risk score (GRS) for increased circulating iron. RESULTS: We found a U-shaped association between iron intake and risk of GAD antibody as the first autoantibody. In children with GRS ≥2 iron risk alleles, high iron intake was associated with an increased risk of IA, with insulin as first autoantibody (adjusted hazard ratio 1.71 [95% CI 1.14; 2.58]) compared with moderate iron intake. CONCLUSIONS: Iron intake may alter the risk of IA in children with high-risk HLA haplogenotypes.

Is staff consistency important to parents' satisfaction in a longitudinal study of children at risk for type 1 diabetes: the TEDDY study.

BACKGROUND: Participants' study satisfaction is important for both compliance with study protocols and retention, but research on parent study satisfaction is rare. This study sought to identify factors associated with parent study satisfaction in The Environmental Determinants of Diabetes in the Young (TEDDY) study, a longitudinal, multinational (US, Finland, Germany, Sweden) study of children at risk for type 1 diabetes. The role of staff consistency to parent study satisfaction was a particular focus. METHODS: Parent study satisfaction was measured by questionnaire at child-age 15 months (5579 mothers, 4942 fathers) and child-age four years (4010 mothers, 3411 fathers). Multiple linear regression analyses were used to identify sociodemographic factors, parental characteristics, and study variables associated with parent study satisfaction at both time points. RESULTS: Parent study satisfaction was highest in Sweden and the US, compared to Finland. Parents who had an accurate perception of their child's type 1 diabetes risk and those who believed they can do something to prevent type 1 diabetes were more satisfied. More educated parents and those with higher depression scores had lower study satisfaction scores. After adjusting for these factors, greater study staff change frequency was associated with lower study satisfaction in European parents (mothers at child-age 15 months: - 0.30,95% Cl - 0.36, - 0.24, p < 0.001; mothers at child-age four years: -0.41, 95% Cl - 0.53, - 0.29, p < 0.001; fathers at child-age 15 months: -0.28, 95% Cl - 0.34, - 0.21, p < 0.001; fathers at child-age four years: -0.35, 95% Cl - 0.48, - 0.21, p < 0.001). Staff consistency was not associated with parent study satisfaction in the US. However, the number of staff changes was markedly higher in the US compared to Europe. CONCLUSIONS: Sociodemographic factors, parental characteristics, and study-related variables were all related to parent study satisfaction. Those that are potentially modifiable are of particular interest as possible targets of future efforts to improve parent study satisfaction. Three such factors were identified: parent accuracy about the child's type 1 diabetes risk, parent beliefs that something can be done to reduce the child's risk, and study staff consistency. However, staff consistency was important only for European parents. TRIAL REGISTRATION: NCT00279318 .

Children's erythrocyte fatty acids are associated with the risk of islet autoimmunity.

Our aim was to investigate the associations between erythrocyte fatty acids and the risk of islet autoimmunity in children. The Environmental Determinants of Diabetes in the Young Study (TEDDY) is a longitudinal cohort study of children at high genetic risk for type 1 diabetes (n = 8676) born between 2004 and 2010 in the U.S., Finland, Sweden, and Germany. A nested case-control design comprised 398 cases with islet autoimmunity and 1178 sero-negative controls matched for clinical site, family history, and gender. Fatty acids composition was measured in erythrocytes collected at the age of 3, 6, and 12 months and then annually up to 6 years of age. Conditional logistic regression models were adjusted for HLA risk genotype, ancestry, and weight z-score. Higher eicosapentaenoic and docosapentaenoic acid (n - 3 polyunsaturated fatty acids) levels during infancy and conjugated linoleic acid after infancy were associated with a lower risk of islet autoimmunity. Furthermore, higher levels of some even-chain saturated (SFA) and monounsaturated fatty acids (MUFA) were associated with increased risk. Fatty acid status in early life may signal the risk for islet autoimmunity, especially n - 3 fatty acids may be protective, while increased levels of some SFAs and MUFAs may precede islet autoimmunity.

Development of a harmonized food grouping system for between-country comparisons in the TEDDY Study.

The Environmental Determinants of Diabetes in the Young (TEDDY) is an international study aiming to investigate associations between dietary and other environmental factors and the risk of developing islet autoimmunity and type 1 diabetes. Dietary intake was assessed using a 24-hour recall and repeated 3-day food records and analyzed using country-specific food composition databases (FCDBs) in Finland, Germany, Sweden, and the U.S. with respective in-house calculation programs. A food grouping harmonization process between four country-specific FCDBs was conducted to evaluate and achieve comparability on food group definitions and quantification of food consumption across the countries. Systematic review revealed that the majority of existing food groups of the TEDDY FCDBs were not comparable. Therefore, a completely new classification system of 15 mutually exclusive main food groups (e.g. vegetables) and 89 subgroups (e.g. root vegetables, leafy vegetables) was developed. Foods and beverages were categorized into basic foods (single ingredient) and composite dishes (multiple ingredients). Composite dishes were broken down to ingredients using food composition data available in the FCDBs or generic recipes created for the harmonization effort. The daily consumption of every food group across FCDBs was quantified consistently as either raw or prepared weight depending on the food group to achieve maximal comparability.

Intake of Energy and Protein is Associated with Overweight Risk at Age 5.5 Years: Results from the Prospective TEDDY Study.

OBJECTIVE: The associations of energy, protein, carbohydrate, and fat intake with weight status up to the age of 5.5 years were prospectively assessed in The Environmental Determinants of Diabetes in the Young (TEDDY) study. METHODS: Food record data (over 3 days) and BMI measurements between 0.25 and 5.5 years were available from 5,563 children with an increased genetic risk for type 1 diabetes followed from shortly after birth. Odds ratios (ORs) were calculated for overweight and obesity by previous intake of energy, protein, carbohydrate, and fat with adjustment for potential confounders. RESULTS: Having overweight or obesity at the age of 5.5 years was positively associated with mean energy intake in previous age intervals (e.g., adjusted OR [95% CI] for overweight: 1.06 [1.04-1.09] per 100 kcal intake at the age of 4.5-5.0 years) and with protein intake after the age of 3.5 and 4.5 years, respectively (e.g., adjusted OR for overweight: 1.06 [1.03-1.09] per 1% of energy intake at the age of 4.5-5.0 years). The respective associations with carbohydrate and fat intake were less consistent. CONCLUSIONS: These findings indicate that energy and protein intake are positively associated with increased risk for overweight in childhood but yield no evidence for potential programming effects of protein intake in infancy.

Association of Early Exposure of Probiotics and Islet Autoimmunity in the TEDDY Study.

IMPORTANCE: Probiotics have been hypothesized to affect immunologic responses to environmental exposures by supporting healthy gut microbiota and could therefore theoretically be used to prevent the development of type 1 diabetes mellitus (T1DM)-associated islet autoimmunity. OBJECTIVE: To examine the association between supplemental probiotic use during the first year of life and islet autoimmunity among children at increased genetic risk of T1DM. DESIGN, SETTING, AND PARTICIPANTS: In this ongoing prospective cohort study that started September 1, 2004, children from 6 clinical centers, 3 in the United States (Colorado, Georgia/Florida, and Washington) and 3 in Europe (Finland, Germany, and Sweden), were followed up for T1DM-related autoantibodies. Blood samples were collected every 3 months between 3 and 48 months of age and every 6 months thereafter to determine persistent islet autoimmunity. Details of infant feeding, including probiotic supplementation and infant formula use, were monitored from birth using questionnaires and diaries. We applied time-to-event analysis to study the association between probiotic use and islet autoimmunity, stratifying by country and adjusting for family history of type 1 diabetes, HLA-DR-DQ genotypes, sex, birth order, mode of delivery, exclusive breastfeeding, birth year, child's antibiotic use, and diarrheal history, as well as maternal age, probiotic use, and smoking. Altogether 8676 infants with an eligible genotype were enrolled in the follow-up study before the age of 4 months. The final sample consisted of 7473 children with the age range of 4 to 10 years (as of October 31, 2014). EXPOSURES: Early intake of probiotics. MAIN OUTCOMES AND MEASURES: Islet autoimmunity revealed by specific islet autoantibodies. RESULTS: Early probiotic supplementation (at the age of 0-27 days) was associated with a decreased risk of islet autoimmunity when compared with probiotic supplementation after 27 days or no probiotic supplementation (hazard ratio [HR], 0.66; 95% CI, 0.46-0.94). The association was accounted for by children with the DR3/4 genotype (HR, 0.40; 95% CI, 0.21-0.74) and was absent among other genotypes (HR, 0.97; 95% CI, 0.62-1.54). CONCLUSIONS AND RELEVANCE: Early probiotic supplementation may reduce the risk of islet autoimmunity in children at the highest genetic risk of T1DM. The result needs to be confirmed in further studies before any recommendation of probiotics use is made.

Factors associated with longitudinal food record compliance in a paediatric cohort study.

OBJECTIVE: Non-compliance with food record submission can induce bias in nutritional epidemiological analysis and make it difficult to draw inference from study findings. We examined the impact of demographic, lifestyle and psychosocial factors on such non-compliance during the first 3 years of participation in a multidisciplinary prospective paediatric study. DESIGN: The Environmental Determinants of Diabetes in the Young (TEDDY) study collects a 3 d food record quarterly during the first year of life and semi-annually thereafter. High compliance with food record completion was defined as the participating families submitting one or more days of food record at every scheduled clinic visit. SETTING: Three centres in the USA (Colorado, Georgia/Florida and Washington) and three in Europe (Finland, Germany and Sweden). SUBJECTS: Families who finished the first 3 years of TEDDY participation (n 8096). RESULTS: High compliance was associated with having a single child, older maternal age, higher maternal education and father responding to study questionnaires. Families showing poor compliance were more likely to be living far from the study centres, from ethnic minority groups, living in a crowded household and not attending clinic visits regularly. Postpartum depression, maternal smoking behaviour and mother working outside the home were also independently associated with poor compliance. CONCLUSIONS: These findings identified specific groups for targeted strategies to encourage completion of food records, thereby reducing potential bias in multidisciplinary collaborative research.

Gluten consumption during late pregnancy and risk of celiac disease in the offspring: the TEDDY birth cohort.

BACKGROUND: Maternal diet during pregnancy has been proposed to increase the risk of autoimmune diseases. OBJECTIVE: The objective was to investigate the association between maternal consumption of gluten-containing foods during late pregnancy and subsequent risk of celiac disease in the offspring. DESIGN: Genetically susceptible children prospectively followed from birth were screened annually for tissue transglutaminase autoantibodies (tTGAs). Children testing persistently positive for tTGAs were further evaluated for celiac disease. Diagnosis of celiac disease was confirmed by intestinal biopsy or was considered likely if the mean tTGA concentration was >100 units in 2 consecutive samples. A questionnaire on the mother's diet in late pregnancy was completed by 3-4.5 mo postpartum. Mothers were divided into 3 groups based on the tertiles of their consumption of gluten-containing foods (servings/d). The association between maternal gluten-containing food consumption and the risk of celiac disease was studied by using a time-to-event analysis. RESULTS: At the time of analysis, 359 (5%) of the 6546 children developed celiac disease. Compared with the middle category of maternal gluten-containing food consumption (servings/d), low (HR: 0.87; 95% CI: 0.67, 1.13; P = 0.296) and high (HR: 0.84; 95% CI: 0.65, 1.09; P = 0.202) consumption was not associated with risk of celiac disease in the child after adjustment for country, human leukocyte antigen genotype, family history of celiac disease, maternal education, and sex of the child. Median maternal daily consumption frequency of gluten-containing foods was higher (P < 0.0001) in Finland (5.3; IQR: 3.9-6.9), Germany (4.3; IQR: 3.1-5.5), and Sweden (3.7; IQR: 2.8-4.9) than in the United States (3.4; IQR: 2.3-4.9). No significant interaction was found between country of residence and the mothers' consumption of gluten-containing foods in relation to risk of celiac disease. CONCLUSION: The frequency of gluten-containing food consumption during late pregnancy is not associated with risk of celiac disease in the offspring.

Clinical features of celiac disease: a prospective birth cohort.

OBJECTIVES: To investigate clinical features of celiac disease (CD) and their association with risk factors for CD in a genetic risk birth cohort. METHODS: Children from 6 clinical centers in 4 countries positive for HLA-DR3-DQ2 or DR4-DQ8 were annually screened for tissue transglutaminase antibodies (tTGA) and assessed for symptoms by questionnaires. Associations of symptoms with anthropometrics, known risk factors for CD, tTGA levels, and mucosal lesions in those biopsied were examined. RESULTS: Of 6706 screened children, 914 developed persistent positive tTGA, 406 underwent biopsies, and 340 had CD. Compared with age-matched tTGA-negative children, those with persistent tTGA were more likely to have symptoms at 2 (34% vs 19%, P < .001) and 3 years of age (28% vs 19%, P = .009) but not at 4 years (27% vs 21%, NS). Z-scores for height, weight, and BMI did not differ between groups. In children with persistent tTGA, having ≥ 1 symptom was associated with family history of CD (odds ratio = 2.59, 95% confidence interval, 1.21-5.57) but not with age, gender, or HLA-DR3-DQ2 homozygosity. At seroconversion, tTGA levels were higher in symptomatic than asymptomatic children (P < .001), in those from CD families (P < .001), and in US participants (P < .001) but not associated with age, gender, or HLA genotype. tTGA levels correlated with severity of mucosal lesions both in symptomatic (r = 0.53, P < .001) and asymptomatic children (r = 0.22, P = .01). CONCLUSIONS: A majority of children detected with persistent tTGA in screenings are asymptomatic and have normal growth by age 4 years. tTGA levels correlate more strongly with severity of mucosal lesions in symptomatic as compared with asymptomatic children.

Age at gluten introduction and risk of celiac disease.

OBJECTIVES: The goal of this study was to determine whether age at introduction to gluten was associated with risk for celiac disease (CD) in genetically predisposed children. METHODS: TEDDY (The Environmental Determinants of Diabetes in the Young) is a prospective birth cohort study. Newborn infants (N = 6436) screened for high-risk HLA-genotypes for CD were followed up in Finland, Germany, Sweden, and the United States. Information about infant feeding was collected at clinical visits every third month. The first outcome was persistent positive for tissue transglutaminase autoantibodies (tTGA), the marker for CD. The second outcome was CD, defined as either a diagnosis based on intestinal biopsy results or on persistently high levels of tTGA. RESULTS: Swedish children were introduced to gluten earlier (median: 21.7 weeks) compared with children from Finland (median: 26.1 weeks), Germany, and the United States (both median: 30.4 weeks) (P < .0001). During a median follow-up of 5.0 years (range: 1.7-8.8 years), 773 (12%) children developed tTGA and 307 (5%) developed CD. Swedish children were at increased risk for tTGA (hazard ratio: 1.74 [95% CI: 1.47-2.06]) and CD (hazard ratio: 1.76 [95% CI: 1.34-2.24]) compared with US children, respectively (P < .0001).Gluten introduction before 17 weeks or later than 26 weeks was not associated with increased risk for tTGA or CD, adjusted for country, HLA, gender, and family history of CD, neither in the overall analysis nor on a country-level comparison. CONCLUSIONS: In TEDDY, the time to first introduction to gluten introduction was not an independent risk factor for developing CD.

Infant feeding patterns in families with a diabetes history - observations from The Environmental Determinants of Diabetes in the Young (TEDDY) birth cohort study.

OBJECTIVE: To assess the association between diabetes family history and infant feeding patterns. DESIGN: Data on breast-feeding duration and age at first introduction of cow's milk and gluten-containing cereals were collected in 3-month intervals during the first 24 months of life. SETTING: Data from the multicentre TEDDY (The Environmental Determinants of Diabetes in the Young) study, including centres in the USA, Sweden, Finland and Germany. SUBJECTS: A total of 7026 children, including children with a mother with type 1 diabetes (T1D; n 292), gestational diabetes mellitus (GDM; n 404) or without diabetes but with a father and/or sibling with T1D (n 464) and children without diabetes family history (n 5866). RESULTS: While exclusive breast-feeding ended earlier and cow's milk was introduced earlier in offspring of mothers with T1D and GDM, offspring of non-diabetic mothers but a father and/or sibling with T1D were exclusively breast-fed longer and introduced to cow's milk later compared with infants without diabetes family history. The association between maternal diabetes and shorter exclusive breast-feeding duration was attenuated after adjusting for clinical variables (delivery mode, gestational age, Apgar score and birth weight). Country-specific analyses revealed differences in these associations, with Sweden showing the strongest and Finland showing no association between maternal diabetes and breast-feeding duration. CONCLUSIONS: Family history of diabetes is associated with infant feeding patterns; however, the associations clearly differ by country, indicating that cultural differences are important determinants of infant feeding behaviour. These findings need to be considered when developing strategies to improve feeding patterns in infants with a diabetes family history.

Use of dietary supplements in pregnant women in relation to sociodemographic factors - a report from The Environmental Determinants of Diabetes in the Young (TEDDY) study.

OBJECTIVES: The aim of the present study was to examine the prevalence and associated factors of dietary supplement use, particularly supplements containing vitamin D and fatty acids, in pregnant women enrolled in a multi-national study. DESIGN: The Environmental Determinants of Diabetes in the Young (TEDDY) study is a prospective longitudinal cohort study. Maternal dietary supplement use was self-reported through questionnaires at month 3 to 4 postpartum. SETTING: Six clinical research centres; three in the USA (Colorado, Georgia/Florida and Washington) and three in Europe (Sweden, Finland and Germany). SUBJECTS: Mothers (n 7326) to infants screened for high-risk HLA-DQ genotypes of type 1 diabetes. RESULTS: Ninety-two per cent of the 7326 women used one or more types of supplement during pregnancy. Vitamin D supplements were taken by 65% of the women, with the highest proportion of users in the USA (80.5 %). Overall, 16% of the women reported taking fatty acid supplements and a growing trend was seen in all countries between 2004 and 2010 (P,0.0001). The use was more common in Germany (32 %) and the USA (24 %) compared with Finland (8.5%) and Sweden (7.0 %). Being pregnant with the first child was a strong predictor for any supplement use in all countries. Low maternal age (<25 years), higher education, BMI<=25.0 kg/m2 and smoking during pregnancy were factors associated with supplement use in some but not all countries. CONCLUSIONS: The majority of the women used dietary supplements during pregnancy. The use was associated with sociodemographic and behavioural factors, such as parity, maternal age, education, BMI and maternal smoking.

Food composition database harmonization for between-country comparisons of nutrient data in the TEDDY Study.

The Environmental Determinants of Diabetes in the Young Study (TEDDY) aims at examining the associations between islet autoimmunity and various environmental exposures, (e.g. diet) in Finland, Germany, Sweden and the United States (US). In order to produce comparable results from dietary assessments, the national food composition databases (FCDB) must contain mutually comparable food composition data. Systematic comparison (definition, unit of measurement, and method of analysis) of energy, protein, fats, carbohydrates, cholesterol, fiber, 13 vitamins, and 8 minerals was carried out among the FCDB of the four countries. Total fat, cholesterol, vitamin A: retinol equivalents and beta-carotene, thiamin, riboflavin, pyridoxine, vitamin B(12), calcium, phosphorus, potassium, magnesium, iron, and zinc are comparable across all four databases. Carbohydrates, fiber, sugars, fatty acids, vitamin D, vitamin E: alpha-tocopherol, vitamin K, vitamin C, pantothenic acid, niacin, manganese, and copper are comparable or can be converted comparable at least across three of the databases. Vitamin E: alpha-tocopherol equivalents, will be comparable across all databases after Finland and Germany subtract tocotrienols from their values. Nitrogen values were added to the Swedish and US databases. After recalculation of protein from nitrogen (Sweden and US), and subtraction of fiber from the total carbohydrate (Finland) followed by recalculations of energy, these values will be comparable across the countries. Starch and folate are not comparable.

Misreporting of energy: prevalence, characteristics of misreporters and influence on observed risk estimates in the Malmö Diet and Cancer cohort.

The present study investigates the prevalence of misreporting of energy in the Malmö Diet and Cancer cohort, and examines anthropometric, socio-economic and lifestyle characteristics of the misreporters. Further, the influence of excluding misreporters on risk estimates of post-menopausal breast cancer was examined. Information of reported energy intake (EI) was obtained from a modified diet history method. A questionnaire provided information on lifestyle and socio-economic characteristics. Individual physical activity level (PAL) was calculated from self-reported information on physical activity at work, leisure time physical activity and household work, and from estimates of hours of sleeping, self-care and passive time. Energy misreporting was defined as having a ratio of EI to BMR outside the 95 % CI limits of the calculated PAL. Logistic regression analysed the risk of being a low-energy reporter or a high-energy reporter. Almost 18 % of the women and 12 % of the men were classified as low-energy reporters, 2.8 % of the women and 3.5 % of the men were classified as high-energy reporters. In both genders high BMI, large waist circumference, short education and being a blue-collar worker were significantly associated with low-energy reporting. High-energy reporting was significantly associated with low BMI, living alone and current smoking. The results add support to the practice of energy adjustment as a means to reduce the influence of errors in risk assessment.