Etude Longitudinale Research Articles

Smoking Trajectories during the Perinatal Period and Their Risk Factors: The Nationally Representative French ELFE (Etude Longitudinale Française Depuis l'Enfance) Birth Cohort Study

Background: In France, rates of perinatal smoking are among the highest worldwide; however, perinatal smoking trajectories and associated factors have still not been adequately researched. Methods: Among women participating in the French nationally representative etude longitudinale française depuis l'enfance birth cohort (n = 15,540), perinatal smoking trajectories were estimated using group-based modelling. Associated characteristics were studied using multinomial logistic regression. Results: Four trajectories were identified: non-smokers (59%), quitters (20%), persistent moderate (12%) and persistent heavy (9%) smokers. Older age, being native French, low socioeconomic position, persistent psychological difficulties and alcohol use in pregnancy, lack of social support, partner's smoking, mistimed pregnancy, and child formula feeding at birth were associated with persistent heavy smoking. Most of these factors were also associated, but to a lesser extent, with persistent moderate smoking, except for age and migrant status, which had opposite effects. Women who successfully lost weight prior to pregnancy had higher levels of quitting smoking. Conclusion: Women's long-term smoking trajectories vary in terms of initial tobacco consumption level but also in relation to socio-demographic, psychological, behavioral and partner characteristics. Health professionals in contact with pregnant smokers should address perceived risks and benefits of smoking, including partner's smoking and weight-gain concerns.

Use of infant formula in the ELFE study: The association with social and health-related factors.

Breastfeeding is recommended until 6months of age, but a wide range of infant formula is available for nonbreastfed or partially breastfed infants. Our aim was to describe infant formula selection and to examine social- and health-related factors associated with this selection. Analyses were based on 13,291 infants from the French national birth cohort Etude Longitudinale Française depuis l'Enfance. Infant diet was assessed at Month 2 by phone interview and monthly from Months 3 to 10 via internet/paper questionnaires. Infant formulas were categorized in 6 groups: extensively or partially hydrolysed, regular with or without prebiotics/probiotics, and thickened with or without prebiotics/probiotics. Associations between type of infant formula used at 2months and family or infant characteristics were assessed by multinomial logistic regressions. At Month 2, 58.1% of formula-fed infants were fed with formula enriched in prebiotics/probiotics, 31.5% with thickened formula, and 1.4% with extensively hydrolysed formula. The proportion of formula-fed infants increased regularly, but the type of infant formula used was fairly stable between 2 and 10months. At Month 2, extensively hydrolysed formulas were more likely to be used in infants with diarrhoea or regurgitation problems. Partially hydrolysed formulas were more often used in families with high income, with a history of allergy, or with infants with regurgitation issues. Thickened formulas were used more with boys, preterm infants, infants with regurgitation issues, or in cases of early maternal return to work. The main factors related to the selection of infant formula were family and infant health-related ones.

Breastfeeding, Early Nutrition, and Adult Body Fat

To examine the association between breastfeeding and adult body fatness, adjusting for nutritional intake in early childhood. Nutritional intakes of 73 healthy infants born in 1984 who participated in the 2-decade-long Longitudinal Study of Nutrition and Growth in Children (Etude Longitudinale Alimentation Nutrition Croissance des Enfants [ELANCE]) were estimated at age 10 months and again at age 2 years. Breastfeeding was defined as any breastfeeding, including partial breastfeeding, regardless of duration. At age 20 years, weight, height, subscapular skinfold thickness (SF), and fat mass (assessed via bioelectrical impedance analysis) were measured. In this sample, 64% of the children had been breastfed. In linear regression models adjusted for mother's body mass index and father's profession, breastfeeding was not associated with any of the body fat measurements at 20 years (all P > .05). After adding nutritional intake variables (total energy and % energy from nutrients) to the models, breastfeeding became significantly associated with lower SF at 20 years. In particular, breastfed subjects had significantly lower % SF at 20 years after adjustment for energy and % fat intakes at 2 years of age, (β=-28.25% SF; 95% CI, -50.28% to -6.21%; P = .013) or when adjusting for energy and % carbohydrates at 2years of age (β = -28.27% SF; 95% CI, -50.64% to -5.90%; P = .014). Breastfeeding was not associated with adult body fatness taking into account the usual confounding factors. However, after also adjusting for nutritional intake covariates, a protective effect of breastfeeding emerged. Early nutrition needs to be taken into account when examining the long-term health effects of breastfeeding.

QPCR standard operating procedure for measuring microorganisms in dust from dwellings in large cohort studies

The aim of the present study was to assess performance, feasibility and relevance of a Standard Operational Procedure (SOP) for large-scale use in the microbial analysis of children's indoor environments.We analyzed dust settled on Electrostatic Dust Fall Collectors (EDCs) by using qPCR which targeted 6 molds, 3 bacteria and 1 mite, chosen for their involvement in allergic or inflammatory processes. Six types of commercialized electrostatic wipes were tested for their releasing capacity of fungal DNA from fungal spores captured by the wipes. Specificity, repeatability and detection limits of the qPCR procedure were tested using calibrated microbial suspensions. The feasibility and relevance of this sampling and analysis method were assessed in a 75-home pilot study.Our result showed that one specific make of wipe was more effective than the others in releasing fungal DNA. qPCR procedure showed good repeatability. The quantification limit was about 5fgDNA/μL for all species except Penicillium chrysogenum (0.5fgDNA/μL) and Dermatophagoïdes pteronyssinus (10fgDNA/μL). No cross-reactivity was observed.DNA concentrations in the 53/75 homes participating in the pilot study were between 0 and 24 625, 0 and 69 738 equivalent cells per cm2 for the fungi and bacteria, and between 0 and 1 equivalent mites per cm2 for D. pteronyssinus. Using the SOP described, we were able to classify the 53 dwellings from the least to the most contaminated according to the quantity of DNA measured for each species.Our SOP measured fungi, bacteria and mites using a cost-efficient, discreet and well-accepted sampling method with just one qPCR tool. The whole procedure can be used for microbial analysis in large cohort studies such as the ELFE study (“Etude Longitudinale Française depuis l'Enfance”) and could help improve our understanding of the interactions between the environment, allergic diseases and child development.

Association of nutrition in early life with body fat and serum leptin at adult age

There is overwhelming evidence that experiences during early life could have long-term health consequences. However, the role of early nutrition in programming obesity and leptin resistance is still poorly understood. We aimed at determining whether nutritional intakes in early life are associated with body composition and hormonal status at 20 years. Healthy infants participating in the two-decade-long prospective ELANCE (Etude Longitudinale Alimentation Nutrition Croissance des Enfants) study were examined at 10 months and 2 years. At 20 years, weight, height, subscapular and triceps skinfold thicknesses, fat mass (FM) and fat-free mass (FFM) assessed via bioelectrical impedance analysis, and serum leptin concentration were recorded in 73 subjects still participating in the follow-up. In adjusted linear regression models, an increase by 100 kcal in energy intake at 2 years was associated with higher subscapular skinfold thickness (β=6.4% SF, 95% confidence interval 2.53-10.30, P=0.002) and higher FFM (0.50 kg, 0.06-0.95, P=0.03) at 20 years. An increase by 1% energy from fat at 2 years was associated with lower subscapular skinfold thickness (-2.3% SF, -4.41 to -0.18, P=0.03), lower FM (-0.31 kg, -0.60 to -0.01, P=0.04) and lower serum leptin concentration (-0.21 μg l(-1), -0.39 to -0.03, P=0.02) at 20 years. Low-fat intake in early life was negatively associated with body fat (particularly at the trunk site) and serum leptin concentration at 20 years, suggesting that early low-fat intake could increase the susceptibility to develop overweight and leptin resistance at later ages. These findings substantiate current recommendations against restricting fat intake in early life and open new directions for investigating the origin of obesity.

Highlights of recent studies and future plans for the French human biomonitoring (HBM) programme

This manuscript presents highlights of recent studies and perspectives from the French human biomonitoring (HBM) programme. Until recently, HBM studies focused on specific populations or pollutants to gain a better understanding of exposure to environmental chemicals, to help regulators reduce environmental exposure and to monitor existing policies on specific concerns. Highlights of recent multicentre biomonitoring studies with specific population or pollutant focus are given. These French HBM studies have been implemented to know: (1) the influence of living near an incinerator on serum dioxin and polychlorinated biphenyl (PCB) levels, (2) the influence of consuming river fish contaminated by PCBs on serum PCBs of fishermen, and (3) the evolution of blood lead levels in children from 1 to 6 years old since 1995. Special emphasis is placed on the use of an integrated (HBM coupled with nutrition and health studies), multipollutant approach. This approach has been initiated in France with a recent national population-based biomonitoring survey, the Etude Nationale Nutrition Santé (ENNS; French Nutrition and Health Survey). This survey will provide the first reference distribution for 42 biomarkers in the French population. The current national HBM strategy will build upon the ENNS and include a national survey of people aged between 6 and 74 years complemented for the neonatal period and childhood by the Etude Longitudinale Française depuis l'Enfance (ELFE; French longitudinal study of children). France also contributes to the harmonization of HBM activities in Europe through participation in European HBM projects.

A Pilot Study of the ELFE Longitudinal Cohort: Feasibility and Preliminary Evaluation of Biological Collection

Etude Longitudinale Française depuis l'Enfance (ELFE) will be a national French cohort of 20,000 children followed from birth to adulthood. Biological samples will be taken at birth to evaluate the fetal exposition to several substances. A pilot study was carried out in October 2007 to test the preanalytical factors that affected sample quality. A variety of fractions were collected by the midwife after delivery from different blood collection tubes. Options in the collection process were 2 daily transports of samples, centralized and standardized processing methodology, and storage of multiple aliquots in liquid nitrogen or at -80°C. We analyzed preanalytical factors that could have affected coagulation and then soluble CD40 Ligand (sCD40L) as a quality control tool for serum quality. Cord blood and urine were collected from 82% and 84% of women, respectively, who agreed to be followed up in the ELFE project. The use of syringe was the main factor correlated with coagulation (relative risk: 2.79 [1.47; 5.31], P<0.01). Maternity unit status was also associated with coagulation (RR: 1.48 [1.03; 2.13] in a private maternity unit vs. a public maternity) as well as time between collection and centrifugation (RR 1.03 [1; 1.07] when time between collection and centrifugation increases from 1 h). There were no extremely low sCD40L values indicating extreme exposures to room temperatures. This first evaluation study allowed us to stress the importance of carefully recording all potentially critical preanalytical variables that might be used at a large-scale level.

The cumulative effect of small dietary changes may significantly improve nutritional intakes in free-living children and adults

The ELPAS (Etude Longitudinale Prospective Alimentation et Santé) study was an 8-month randomized controlled dietary modification trial designed to test the hypothesis that family dietary coaching would improve nutritional intakes and weight control in 2026 free-living children and parents. It resulted in significant nutritional changes, with beneficial effects on body mass index in adults. In these ancillary analyses, we investigated dietary changes throughout the intervention. Before the study, modeling analyses were carried out on the French Association Sucre Produits Sucrés Consommation et Communication (ASPCC) food-consumption database to identify the most efficient dietary intervention strategy. During the study, all participants performed monthly three nonconsecutive 24-h dietary recalls: this allowed for measuring changes in the number of servings per day and serving size for each targeted food category throughout the intervention. Modeling analyses showed that targeting only the 10 main foods contributing to fat and carbohydrate intakes did not allow for reaching the ELPAS nutritional goals. As a result, it was decided to target more foods and to propose several types of dietary advice (such as change in serving size, change in cooking method, food substitution). This strategy led to many appropriate dietary changes during the intervention, but only a few of them reached significance. The mean number of servings per day was indeed significantly modified for only 7% of the targeted food categories in children and 17% in parents. The mean serving size was modified for only 12% of targeted food categories in children and 9% in parents. The cumulative effect of small dietary changes may induce significant nutritional improvements, with limited burden for populations.

School Experience and Reflection: An On-Going Study of Teachers' Views and Students' Experience

Most teacher-education programmes aim to develop students into reflective practitioners who are independent learners with skills of critical analysis and evaluation. This article outlines preliminary evidence from a longitudinal study of teacher training at the University of Strathclyde where it is attempted to identify effective strategies, both within in-faculty and school experience components, for the development of those skills. Differences in support needed at different phases of placement are discussed and the variation in teachers' perceptions of their role, and the appropriate timing of skill development are explored. Résumé La plupart des programmes de formation d'enseignants visent à faire de leurs étudiants des praticiens réfléchis, "apprenants" indépendants dotés de la capacité critique d'analyse et d'évaluation. L'article trace les grands traits de cette évidence à partir d'une étude longitudinale de la formation des enseignants à l'Université de Strathclyde où nous tentons d'analyser des stratégies efficaces pour développer cette capacité, à la fois dans le cadre universitaire et dans la pratique pédagogique. Les différences dans le soutien nécessaire aux différentes phases de la mise en place sont étudiées et les variations de représentations de leur rôle par les enseignants ainsi que le rythme adéquat du développement de cette capacité sont analysées. (Traduction: Claude Carpentier, Sciences humaines et sociales, Université de Picardie Jules Verne, Amiens)

Lactation and Pregnancy: A Hypothesis

After a brief review of existing studies on the subject an hypothesis concerning the relationship which is known to exist but remains to be clarified between lactation and anovulation is presented. This relationship is a common subject of folklore and folk medicine but is yet to be dealt with by science. It is noted that the majority of scientific studies concerning lactation were performed in Western developed countries where cultural mores result in faster weaning and earlier introduction of supplementary foods. However in many countries and areas of the world lactation is continued for 4 years in nearly 100% of cases. Studies have also noted a relationship between onset of postpartum menstruation and mothers socioeconomic levels with lower-economic-scale women menstruating postpartum later than women from higher socioeconomic classes. In view of this evidence it is suggested that the process of lactation as it occurs among peasant and undeveloped populations is generally not comparable to that which occurs in highly industrialized cultures (U.S. or Europe). In the former group lactation tends to be a long-term intensive process which includes frequent nonscheduled stimulations of the breast which may inhibit ovulation until later when the child is weaned to other foods. In comparison developed nations with greater access to pediatric care begin supplementing breastfeeding with foods at earlier ages thereby decreasing the frequency and duration of feedings. Such children are generally weaned by age 1 year and these practices seem to lead to early resumption of ovarian function. This hypothesis is said to account for the fact that in modern studies the relationship between sterility and lactation has been obscured.