Social Inequalities in Young Children’s Lifestyle Behaviors and Childhood Overweight

__Abstract__ Childhood overweight and obesity is a major public health concern. Adverse health and psychosocial outcomes associated with childhood overweight include elevated blood pressure and hypertension, type 2 diabetes, asthma, sleeping disorders, low self-esteem, and decreased quality of life. Long term consequences of childhood overweight include the persistence (or tracking) of overweight from childhood into adulthood and the increased risk of cardiovascular morbidity and premature mortality. Over the past three decades, the prevalence of childhood overweight and obesity has risen markedly. The current prevalence of overweight varies across continents; North America, Europe, and parts of the Western Pacific have the highest prevalence with 20-30% of all children being overweight [8]. In the Netherlands, regular nationwide growth studies are conducted among children aged 0-21 years. Comparison of findings over the past three decades has shown a two- to three-fold increase in overweight prevalence and a four- to six-fold increase in obesity prevalence among native Dutch children. In the most recent study, conducted in 2009, the prevalence of overweight (including obesity) was 13.3% and 14.9% for native Dutch boys and girls, respectively

Independent associations between sedentary time, moderate-to-vigorous physical activity, cardiorespiratory fitness and cardio-metabolic health : a cross-sectional study

We aimed to study the independent associations of sedentary time (ST), moderate-to-vigorous physical activity (MVPA), and objectively measured cardiorespiratory fitness (CRF) with clustered cardio-metabolic risk and its individual components (waist circumference, fasting glucose, HDL-cholesterol, triglycerides and blood pressure). We also investigated whether any associations between MVPA or ST and clustered cardio-metabolic risk were mediated by CRF. MVPA, ST, CRF and individual cardio-metabolic components were measured in a population-based sample of 341 adults (age 53.8 +/- 8.9 years; 61% men) between 2012 and 2014. MVPA and ST were measured with the SenseWear pro 3 Armband and CRF was measured with a maximal exercise test. Multiple linear regression models and the product of coefficients method were used to examine independent associations and mediation effects, respectively. Results showed that low MVPA and low CRF were associated with a higher clustered cardio-metabolic risk (beta = -0.26 and beta = -0.43, both p<0.001, respectively). CRF explained 73% of the variance in the association between MVPA and clustered cardio-metabolic risk and attenuated this association to non-significance. After mutual adjustment for MVPA and ST, CRF was the most important risk factor for a higher clustered cardio-metabolic risk (beta = -0.39, p<0.001). In conclusion, because of the mediating role of CRF, lifestyle-interventions need to be feasible yet challenging enough to lead to increases in CRF to improve someone's cardio-metabolic health

Modelling the microbial quality and safety of foods

Quality and safety of foods are often influenced by the presence and growth of microorganisms. Microorganisms in foods can be divided into two groups: pathogenic organisms, causing illness, and microorganisms that are not harmful to health, but that can spoil a product. Presence and growth of pathogenic organisms should be avoided as much as possible. Growth of spoilage organisms is allowed to a certain extent. Presence and growth of pathogenic microorganisms largely influences food safety, whereas growth of spoilage organisms, generally determines shelf life of a food product, Food quality is assumed to be influenced by both pathogenic organisms and spoilage organisms.A method to predict microbial safety and quality of foods is presented. The construction of a food product from its ingredients is simulated, following a recipe. Food processing heuristics are combined with models developed in predictive microbiology. Parameter values of ingredients of foods, such as water activity and acidity, and models for microbial growth and decay are used for prediction. The values of these parameters are collected and present in databases. If required information is lacking, methods to make reliable guesses of the parameters are developed. Furthermore, expert knowledge in production and development of foods can be applied to improve the quality of prediction. Shelf life can be calculated as a function of fluctuating temperature in time. Several food distribution chains can be simulated to assess the influence of distribution chains on food quality. The described methods are implemented into a computerised decision support system.Mathematical models for microbial growth, implemented in the decision support system, are given more attention to. Microbiological food quality is examined by modelling bacterial growth of a spoilage bacterium; Lactobacillus curvatus. Microbiological food safety is modelled by assessing growth behaviour of a pathogenic bacterium; Listeria monocytogenes.Models that describe the effect of acidity, temperature, and the combined effect of these variables on the growth parameters of Lactobacillus curvatus are developed and validated. Growth parameters (lag time, specific growth rate, and maximum population density) are calculated from growth data at various temperature-acidity combinations. The effect of acidity is monitored at several constant temperature values. Models are set up and fitted to the data. The same procedure is used at constant acidity values to model the effect of temperature. For lag time, specific growth rate, and maximum population density, the effect of temperature can be multiplied with the effect of acidity. The models are equipped with parameters suggesting that organisms cease growing at minimal or maximal values for controlling variables (Temperature, pH, aw ). Evidence is presented for the existence of a lower and upper acidity boundary value for bacterial growth.The effect of temperature, acidity, and water activity on bacterial growth rate of Lactobacillus curvatus is modelled in an extended model. The model is based on two, earlier developed models, one for growth rate as a function of temperature and water activity and the earlier mentioned model. It is assumed that combinatory effects between acidity and water activity do not exist. Therefore, the two models are multiplied to result into one model. The resulting model is fitted to data sets measured earlier, and the parameters of the model are determined. A new data set with values for controlling variables outside the data range where the model is developed, is used to validate the developed model. The model is found very well able to predict outside the measured data range.Bacterial growth rate of Listeria monocytogenes is modelled as a function of temperature, acidity and water activity, for which two equations are developed. The first equation predicts growth rate at sub optimal acidity values, sub optimal temperatures and sub optimal water activities, the second model predicts growth throughout the entire acidity range. The models are validated statistically and by comparing model predictions with values reported in literature.Finally, a computerised system for the identification of bacteria is developed. The system is equipped with a key to the identification of lactic acid bacteria. The identification is carried out in two steps. The first step distinguishes classes of bacteria by following a decision tree with general identification tests. The second step in the identification is the distinction of species within a class on the basis of biochemical fermentation patterns. During group classification, probabilities for test failure are used. These probabilities can be used for assessing the quality of a given test answer. The probabilities are also used to select the most probable test answer in case of an inconclusive test result. The probabilities of test failure are determined by a group of experts and a group of potential users of the identification system. During species identification, similarity indices are calculated for all bacteria in a class. The described identification system is able to "learn" from different sessions in the species identification step, improving both identification speed and accuracy. Because of the versatile way in which the system is set up, it can very easily be expanded with identification keys to other organisms.Structured models and modelling methods are used to predict changes in quality and safety of foods. This thesis shows that even complex problems such as the prediction of the quality of foods, can be modelled through the combination of several models. Model systems are developed giving insight into the processes that are of importance in the determination of food quality and safety

Sedentary behaviors, physical activity behaviors, and body fat in 6-year-old children: The Generation R Study

Background: Childhood overweight and obesity is a major public health concern. Knowledge on modifiable risk factors is needed to design effective intervention programs. This study aimed to assess associations of children's sedentary behaviors (television viewing and computer game use) and physical activity behaviors (sports participation, outdoor play, and active transport to/from school) with three indicators of body fat, i.e., percent fat mass, body mass index (BMI) standard deviation scores, and weight status (normal weight, overweight). Methods: Cross-sectional data from 5913 6-year-old ethnically diverse children were analyzed. Children's weight and height were objectively measured and converted to BMI. Weight status was defined according to age- and sex-specific cu

Social inequalities in young children's meal skipping behaviors: The Generation R Study

Background: Regular meal consumption is considered an important aspect of a healthy diet. While ample evidence shows social inequalities in breakfast skipping among adolescents, little is known about social inequalities in breakfast skipping and skipping of other meals among young school-aged children. Such information is crucial in targeting interventions aimed to promote a healthy diet in children. Methods: We examined data from 4704 ethnically diverse children participating in the Generation R Study, a population-based prospective cohort study in Rotterdam, the Netherlands. Information on family socioeconomic position (SEP), ethnic background, and meal skipping behaviors was assessed by parent-reported questionnaire when the child was 6 years old. Multiple logistic regression analyses were performed to assess the associations of family SEP (educational level, household income, employment status, family composition) and ethnic backgr

Income inequality and social gradients in children’s height: a comparison of cohort studies from five high-income countries

Background Health and well-being are better, on average, in countries that are more equal, but less is known about how this benefit is distributed across society. Height is a widely used, objective indicator of child health and predictor of lifelong well-being. We compared the level and slope of social gradients in children's height in high-income countries with different levels of income inequality, in order to investigate whether children growing up in all socioeconomic circumstances are healthier in more equal countries. Methods We conducted a coordinated analysis of data from five cohort studies from countries selected to represent different levels of income inequality (the USA, UK, Australia, the Netherlands and Sweden). We used standardised methods to compare social gradients in children's height at age 4-6 years, by parent education status and household income. We used linear regression models and predicted height for children with the same age, sex and socioeconomic circumstances in each cohort. Results The total analytic sample was 37 063 children aged 4-6 years. Gradients by parent education and household income varied between cohorts and outcomes. After adjusting for differences in age and sex, children in more equal countries (Sweden, the Netherlands) were taller at all levels of parent education and household income than children in less equal countries (USA, UK and Australia), with the greatest between-country differences among children with less educated parents and lowest household incomes. Conclusions The study provides preliminary evidence that children across society do better in more equal countries, with greatest benefit among children from the most disadvantaged socioeconomic groups

Meal-Skipping Behaviors and Body Fat in 6-Year-Old Children

Objective To assess the prospective associations of breakfast, lunch, and dinner skipping at age 4 years with body fat (ie, percent fat mass, body mass index [BMI], and weight status) at age 6 years. Study design Data were analyzed from 5913 children participating in the Generation R Study, a population-based prospective cohort study in Rotterdam, The Netherlands. Meal-skipping behaviors were assessed through parent-report questionnaires. Children's weight and height were objectively measured and converted to BMI SDSs. Weight status (ie, overweight or normal weight) was defined according to age- and sex-specific cutoff points. At age 6 years, percent fat mass was assessed by dual-energy X-ray absorptiometry. Linear and logistic regression analyses were performed, adjusting for covariates and BMI at age 4 years. Results Breakfast skipping at age 4 years was associated with a higher percent fa

Early sexual intercourse: Prospective associations with adolescents physical activity and screen time

Objectives: To assess the prospective associations of physical activity behaviors and screen time with early sexual intercourse initiation (i.e., before 15 years) in a large sample of adolescents. Methods: We used two waves of data from the Rotterdam Youth Monitor, a longitudinal study conducted in the Netherlands. The analysis sample consisted of 2,141 adolescents aged 12 to 14 years (mean age at baseline = 12.2 years, SD = 0.43). Physical activity (e.g., sports outside school), screen time (e.g., computer use), and early sexual intercourse initiation were assessed by means of self-report questionnaires. Logistic regression models were tested to assess the associations of physical activity behaviors and screen time (separately and simultaneously) with early sexual intercourse initiation, controlling for confounders (i.e., socio-demographics and substance use). Interaction effects with gender were tested to assess whether these associations differed significantly between boys and girls. Results: The only physical activity behavior that was a significant predictor of early sexual intercourse initiation was sports club membership. Adolescent boys and girls who were members of a sports club) were more likely to have had early sex (OR = 2.17; 95% CI = 1.33, 3.56. Significant gender interaction effects indicated that boys who watched TV ≥2 hours/ day (OR = 2.00; 95% CI = 1.08, 3.68) and girls who used the computer ≥2 hours/day (OR = 3.92; 95% CI = 1.76, 8.69) were also significantly more likely to have engaged in early sex. Conclusion: These findings have implications for professionals in general pediatric healthcare, sexual health educators, policy makers, and parents, who should be aware of these possible prospective links between sports club membership, TV watching (for boys), and computer use (for girls), and early sexual intercourse initiation. However, continued research on determinants of adolescents' early sexual initiation is needed to further contribute to the strategies for improving adolescents' healthy sexual development and behaviors

Prospective associations between measures of gross and fine motor coordination in infants and objectively measured physical activity and sedentary behaviour in childhood

One important determinate of childhood physical activity and sedentary behaviour may be that of motor development in infancy. The present analyses aimed to investigate whether gross and fine motor delays in infants were associated with objective and self-reported activity in childhood. Data were from the UK Millennium Cohort Study, a prospective cohort study, involving UK children born on or around the millennium (September 2000 and January 2002). When children were 9 months old, parents reported children?s fine and gross motor-coordination, and at 7 years, sports club attendance and daily TV viewing time. Children?s physical activity was measured using accelerometers at 7 years. Adjusted regression models were used to examine associations between delayed motor development and objectively measured activity, sport club attendance and TV viewing time. In this sample (n=13021), gross motor delay in infancy was associated with less time in moderate-to-vigorous physical activity (B -5.0 95% CI -6.8, -3.2) and more time sedentary (B 13.5 95% CI 9.3, 17.8) in childhood.Gross and fine motor delays during infancy were associated with a reduced risk of having high attendance at sports clubs in childhood (both RR 0.7, 95% CI 0.6, 0.9). Fine motor delays, but not gross delays, were also associated with an increased risk of having high TV viewing time (RR 1.3 95% CI 1.0, 1.6). Delays in motor development in infancy are associated with physical activity and sedentary time in childhood