Obesity is at epidemic levels among European children, and precursors of type 2 diabetes and cardiovascular disease are now described in children. Additionally, prenatal and early environment are increasingly recognized as important determinants for future chronic disease risk. It has been established that low birth weight is associated with higher metabolic risk in adulthood and metabolic risk in adulthood is highly associated with adulthood obesity, which in turn, is associated with weight gain during childhood. Thus, childhood and adolescence seem to be critical to later metabolic risk (1, 2). In fact, it was suggested that it is the postnatal growth adaptation, rather than low birth weight itself, that more importantly contributes to later disease risk (1, 2).
Several periods of postnatal life have been described as critical to the development of metabolic risk, such as the adiposity rebound and the transition to adolescence (2-11). However, there is uncertainty regarding which of these moments are in fact critical for
adiposity accrual and cardiometabolic risk, consequently providing time windows for prevention.
Analysis of data from across the life course enables us to examine the dynamic ways in which variables of interest change and interact across a person’s life span, determinants of these changes, and how the pattern of change relates to later health. But to use this type of approach truly longitudinal studies are needed.
Birth cohorts are the best way to approach this problem, as children are followed from birth to adulthood, providing an unique opportunity to longitudinally collect information on dynamic variables such as growth and adiposity accrual throughout the life span (12, 13). This methodology can provide fundamental information on fetal and postnatal exposures, amount and pattern of weight gain during childhood and the transition to adolescence (14). This study design also allows assessing the associations between these factors and the development of aetiologies aiming at the reduction of the global burden of disease.
This project is embed in Generation XXI birth cohort, that is an ongoing population-based birth cohort, established in 2005/2006 involving more than 8600 children born in Porto, Portugal. The whole cohort was revaluated two times – at 4 and 7 years of age. Generation XXI is a resource of the Institute of Public Health of University of Porto and has currently diverse means of funding and a well-established research team. The project PI has been the executive coordinator of Generation XXI since 2009.
This project was design to understand the establishment of obesity in childhood and its effects on cardiometabolic health early in life, using a life course approach, identifying critical periods and evaluating cumulative risks. More specifically, this project aims at a) estimating the incidence of obesity and different body fat distribution phenotypes in Portuguese children; b) studying whether the trajectory of growth and development affects cardiometabolic health at 10 years of age; c) evaluating the effect of growth on cardiometabolic health independently of final attained adiposity; d) understanding the impact of the adiposity rebound (early vs.
later) on growth and childhood metabolic risk; e) evaluating the effect of early menarche (≤ 10 years of age) on metabolic risk factors at 10 years of age and how it affects the association between growth and childhood metabolic risk, among girls.
Generation XXI data was collected using structured questionnaires to obtain information on mothers’ and children demographic and lifestyle variables and on past and current medical history. Clinical registries at birth were also used to collect information on delivery, post-partum complications, and anthropometrics at birth. Blood samples from the mother and child have also been collected throughout the years, and data on biochemical and metabolic indicators (e.g. glucose, insulin, blood lipids, adipokines) are available since birth.
From the child health books, all data regarding measures of the child’s weight and length along the years were abstracted allowing the establishment of the childhood growth trajectories for the Portuguese population up to 7 years of age.
The entire cohort will be invited to a follow-up assessment that is planned to begin in 2015. The child (at 10 years of age) will be evaluated using a structured questionnaire, anthropometrics will be evaluated measuring weight, height, and waist, hip, arm, thigh and thoracic circumferences, tetrapolar bioimpedance and in a sub-sample a whole body scan by DXA will be performed. Blood pressure measurements and blood samples will be also collected, for estimating the cardiometabolic risk.
Ethical approval for the study was obtained from relevant institutional ethics committees and all ethical procedures regarding informed consent were followed.