Aurore Camier

BACKGROUND Identifying and selecting relevant scientific evidence is central to evidence-based medicine but challenging to teach early in medical training. Educational interventions have shown inconsistent effects on objectively measured performance, leaving limited evidence on how to improve students’ practical evidence retrieval and selection. OBJECTIVE To evaluate whether adding a brief introduction to citation searching to standard literature-searching instruction improves the relevance and methodological quality of evidence selected by undergraduate medical students. METHODS We conducted a pragmatic controlled quasi-experimental study among second-year medical students in Lille, France. Two pre-existing teaching sessions received the same 45-minute standard literature-searching course. Control students completed the study assessment before, and intervention students after, an additional 15-minute introduction to citation searching, including its automation using BibliZap. BibliZap is an open-source tool for automated multilevel forward and backward citation searching. Students searched 1 of 6 randomly assigned clinical questions for 30 minutes and submitted up to 10 references; BibliZap use was optional and tracked. Two blinded experts independently evaluated academic articles. The primary outcome was the rate of expert top picks, defined as references experts considered particularly important for the assigned question; secondary outcomes assessed relevance and quality. Intention-to-teach analyses compared assigned groups irrespective of BibliZap use; per-use analyses compared controls with intervention students who used BibliZap. Models accounted for the number of references submitted and were adjusted for prespecified participant characteristics. RESULTS Among 450 participating students (79.1% of the class), 222 were controls and 228 intervention students; 71 (31%) intervention students used BibliZap. Median search duration was 21 minutes in both groups (Q1-Q3, 14-28 and 15-27), and the median number of references submitted was 7 (Q1-Q3, 6-8 and 6-9, respectively). In intention-to-teach analyses, citation-searching training increased expert top picks by 14% (incidence rate ratio [IRR] 1.14, 95% CI 1.04-1.25; P=.006), articles experts would include in a talk (IRR 1.10, 95% CI 1.03-1.18; P=.003), and mean relevance grade (+0.30/10, 95% CI 0.20-0.40; P<.001). For expert top picks, the IRR was 1.09 (95% CI 0.98-1.21) with no tracked BibliZap use, 1.24 (95% CI 1.09-1.41) with at least 1 seed, and 1.37 (95% CI 1.14-1.66) with at least 2 seeds. The intervention also reduced nonacademic references by 51% (IRR 0.49, 95% CI 0.33-0.74) and students selected articles with greater methodological rigor (proportional odds ratio 1.42, 95% CI 1.16-1.74; both P<.001). CONCLUSIONS Adding a brief introduction to citation searching to standard literature-searching instruction improved the relevance and quality of evidence selected by undergraduate medical students. These findings support citation searching as a practical component of early literature-searching education and warrant evaluation of whether its benefits persist and generalize beyond a single teaching session.

L’effet protecteur de l’allaitement sur le risque d’obésité est souligné par de nombreuses études. En revanche, peu de ces études ont considéré les autres aspects de l’alimentation précoce. Ainsi, l’objectif principal de cette thèse était de caractériser l’alimentation de la première année de vie, dans sa globalité, puis d’étudier les liens avec la croissance de l’enfant. Dans une première partie, il a été montré qu’il est pertinent de considérer des variables autres que la durée d’allaitement et l’âge de la diversification alimentaire pour caractériser l’alimentation précoce, notamment l’âge d’introduction de certains groupes alimentaires particuliers comme les boissons sucrées et le lait de vache ou encore l’introduction des morceaux. De plus, il ressort que les pratiques d’alimentation précoce recommandées comme l’allaitement ou la diversification alimentaire dans la fenêtre recommandée sont fortement associées entre elles. Des analyses sur les caractéristiques familiales associées à ces pratiques précisent qu’un âge et un niveau d’études maternels élevés sont associés à des pratiques d’allaitement et de diversification plus en accord avec les recommandations, qu’une migration et un faible niveau de revenus sont associés à un allaitement plus long et qu’enfin la présence d’enfants plus âgés dans le foyer est associée à la fois à un allaitement plus long mais aussi à une introduction précoce du lait de vache. Dans une deuxième partie, une analyse a été menée sur les liens entre les pratiques d’alimentation de la première année de vie et la croissance, avec l’étude de l’indice de masse corporelle (IMC) jusqu’à 5 ans ou encore avec le pic et le rebond d’adiposité. Il a été retrouvé que le sexe de l’enfant est un facteur modérateur dans les associations entre les pratiques d’alimentation et la croissance, avec notamment un effet de l’allaitement plus fort chez les filles. Un allaitement plus long est associé à une croissance précoce plus faible, mais les associations retrouvées avec la croissance plus tardive ne sont pas en faveur d’un effet protecteur vis-à-vis du surpoids. Une diversification alimentaire précoce est associée à un IMC plus élevé entre 1 et 5 ans. Les enfants allaités plus longtemps et diversifiés plus tardivement présentent des paramètres de croissance plus faibles la première année mais cette tendance ne se confirme pas systématiquement dans les variables de croissance ultérieures. Enfin, dans une troisième partie, l’influence de la teneur en protéines des préparations infantiles sur la croissance précoce a été étudiée. Cette analyse s’inscrit dans une démarche d’exploration des mécanismes expliquant les liens entre l’alimentation précoce, dont l’allaitement, et la croissance. En effet, des apports élevés en protéines la première année de vie semblent associés à une croissance précoce plus élevée. Cette dernière analyse a permis de confirmer qu’il existe un gradient positif entre la teneur en protéines des préparations infantiles présentes sur le marché et la croissance précoce des enfants : plus la teneur en protéines de la préparation infantile consommée à 4 mois est élevée plus les paramètres de croissance (z-scores du poids, taille et IMC pour l’âge) sont élevés entre 6 et 18 mois. L’ensemble de ces analyses a permis de montrer l’effet de l’alimentation précoce sur la croissance dans l’enfance. Une diversification alimentaire précoce et une teneur en protéines de la préparation infantile élevée sont associées à une croissance précoce plus importante. Les liens entre l’allaitement et la croissance sont plus hétérogènes et ne sont pas tous en faveur d’un effet protecteur de l’allaitement vis-à-vis du risque de surpoids.

Summary: Background/Objectives: The infant diet represents one of the main modifiable determinants of early growth. This study aimed to investigate the associations of infant feeding practices with body mass index (BMI) until 7.5 years.Subjects/Methods: Analyses were based on data from the French nationwide ELFE birth cohort. Data on breastfeeding (BF) and complementary feeding (CF) were collected monthly from 2 to 10 months. Infant feeding practices were characterized using principal component analyses (PCA) and hierarchical ascendant classification. BMI z‐score was computed at 1, 2, 3, 5 and 7.5 years, from data collected in the child's health booklet; 7.5‐year overweight was defined according to IOTF references. Associations between infant feeding practices and BMI were investigated by linear regression models adjusted for main confounders.Results: Ever breastfeeding was not associated with BMI up to 7.5 years. Compared to intermediate breastfeeding duration (1 to <3 months), longer breastfeeding duration (≥6 months) was related to lower 1‐year BMI, but not at older ages. Compared to the recommended age at CF introduction (4–6 months), early CF (<4 months) was related to higher BMI up to 5 years with a similar trend at 7.5 years, but not to the risk of overweight. The PCA patterns characterized by early baby cereal introduction and late food pieces introduction or by frequent intake of main food groups were related to a lower BMI up to 7.5 years.Conclusion: Breastfeeding was related with a lower BMI in infancy but not thereafter, whereas an early CF initiation (<4 months) was associated with a higher BMI in childhood.

Background/Objective High magnitude of adiposity peak and early adiposity rebound are early risk markers of later obesity. Infant diet represents one of the main modifiable determinants of early growth. This study aimed to investigate the association between infant feeding practices and age and magnitude of adiposity peak and rebound. Subjects/Methods Analyses were based on data from the French EDEN mother–child cohort. Data on breastfeeding and complementary feeding were collected at birth and 4, 8, and 12 months. From clinical examinations and measurements collected in the child’s health booklet up to 12 years, individual growth curves were modeled, and ages and magnitudes of adiposity peak and rebound were estimated. Associations between infant feeding practices and growth were investigated by multivariable linear regression in children after testing a child-sex interaction. Results In the studied population (n = 1225), adiposity peak occurred at a mean of 9.9 ± 2 months and adiposity rebound at 5.5 ± 1.4 years. Associations between infant feeding practices and adiposity peak or rebound were moderated by child sex. For girls, each additional month of breastfeeding was related to a 2-day increase in the age at adiposity peak (p < 0.001), and an 18-day increase in the age at adiposity peak (p = 0.004). Whereas for boys, each additional month for the age at complementary food introduction was associated with a 29-day increase in the age at adiposity rebound (p = 0.02). For boys, long breastfeeding duration was only related to reduced body mass index at adiposity peak. Conclusions Child sex has a moderating effect on the association between infant feeding practices and adiposity peak or rebound. The well-known association between breastfeeding duration and early growth seems stronger in girls than boys. The association found for complementary feeding in boys may give new insights into preventing obesity.

Summary: Background: In several systematic reviews, rapid weight gain in early life has been related to increased risk of later obesity. In line with this finding, the “early protein hypothesis” suggests that reducing early protein intake is a potential lever for obesity prevention.Objective: To determine whether the variability of protein content of infant formula used in France over the period 2003‐2012 is significantly associated with early growth in children.Methods: A pooled sample of infants from the EDEN (Etude des Déterminants pré et postnatals de la santé et du développement de l'Enfant) mother‐child cohort (born in 2003‐2006) and the ELFE (Etude Longitudinale Française depuis l'Enfance) birth cohort (born in 2011) (n_total = 5846) was used. Protein content of the infant formula received at 4 months was classified into five groups. Associations between protein content (or breastfed status) at 4 months and weight‐, length‐ and BMI‐for‐age z‐scores at 6, 12 and 18 months were analysed by multivariable linear regression.Results: This analysis showed a positive association between protein content and weight‐, length‐ and BMI‐for‐age z‐scores at 6 months and only for weight‐for‐age at 12 months. At 6 months, as compared with the intermediate protein‐content group (2.1‐2.5 g/100 kcal), infants receiving very‐high protein content (>2.8 g/100 kcal) had higher BMI‐for‐age z‐score and those from the very‐low protein‐content group (<2.0 g/100 kcal) had lower BMI‐for‐age z‐score. Exclusively breastfed infants had lower length and weight z‐scores than formula‐fed infants at any age.Conclusions: Our findings show a positive association, under real conditions of use, between protein contents in infant formula still on the market and weight‐, length‐ and BMI‐for‐age z‐scores from 6 to 18 months.

Family characteristics such as education level or income are related to infant feeding practices. This study aimed to characterize infant feeding practices and investigate their associations with family characteristics. Analyses were performed with data from a French nationwide cohort, Etude Longitudinale Française depuis l’Enfance (ELFE). Feeding practices were characterized by two methods, a principal component analysis and a hierarchical ascendant classification (n = 8922). This characterization was conducted in three steps: considering firstly only introduction of main food groups, then also food pieces and finally adding the type of complementary food. The associations between family characteristics and the infant feeding patterns or clusters were tested by linear or multinomial regressions (n = 7556). Besides breastfeeding duration and age of first introduction of complementary foods, it appeared also important to consider specific food groups such as sweetened beverages and cow’s milk, and the introduction of food pieces, to describe feeding practices. Recommended feeding practices (longer breastfeeding, complementary food in the right period) were related to higher maternal age and education level, so was migration status, the presence of older children, low income or the mothers’ attendance to pre-birth preparation classes. The interrelations between feeding practices and family characteristics must be considered when examining the influence of feeding practices on child’s health.

Organic food consumption and its effects on health remain understudied in adults and in children. The aim of this study was to describe family characteristics associated with feeding infants organic foods during the complementary feeding period. The analysis included 9764 children from the French Étude Longitudinale Française depuis l’Enfance (ELFE) birth cohort. In addition to telephone interviews conducted at 2, 12 and 24 months, a monthly questionnaire about milk feeding and complementary foods (including organic foods) was completed by parents between 3 and 10 months. Associations between family characteristics and feeding with organic foods during complementary feeding were analysed by multivariable multinomial logistic regression. Overall, 51 % of infants never consumed organic food during the complementary feeding period (up to 10 months), 24 % sometimes, 15 % often and 9 % always or almost always. As compared with infants never fed organic foods, those ‘often’ or ‘always’ fed organic foods were born to older mothers, with higher education level or family income, and lower pre-pregnancy BMI. As compared with never-smoking women, women who had stopped smoking before pregnancy were more likely to feed their infant organic foods. Feeding with organic foods was also related to long breast-feeding duration and later introduction to complementary foods. To conclude, associations between feeding with organic foods and family socio-economic position as well as infant feeding practices need to be considered when studying the impact of organic foods on children’s health and development.

Most professional and international organizations recommend folic acid supplementation for women planning pregnancy. Various studies have shown high levels of non-compliance with this recommendation. This study aimed to identify sociodemographic characteristics related to this compliance. The analyses were based on 16,809 women from the French nationwide ELFE cohort (Etude Longitudinale Française depuis l’Enfance). Folic acid supplementation was assessed at delivery, and sociodemographic characteristics were collected at two months postpartum. The association between sociodemographic characteristics and compliance with recommendations on folic acid supplementation (no supplementation, periconceptional supplementation, and supplementation only after the periconceptional period) was examined using multivariate multinomial logistic regression. Only 26% of French women received folic acid supplementation during the periconceptional period, 10% of women received supplementation after the periconceptional period, and 64% received no supplementation. Young maternal age, low education level, low family income, multiparity, single parenthood, maternal unemployment, maternal overweight, and smoking during pregnancy were related to lower likelihood of folic acid supplementation during the periconceptional period compared to no supplementation. These associations were not explained by unplanned pregnancy. Immigrant and underweight women were more likely to receive folic acid supplementation after the periconceptional period. Our study confirms great social disparities in France regarding the compliance with the recommendations on folic acid supplementation.