Early life growth trajectories and future risk for overweight.

OBJECTIVE: Standard approaches have found that rapid growth during the first 2 years of life is a risk factor for overweight in later childhood. Our objective was to test whether growth velocity, independent of concurrent size, was associated with overweight using a nonlinear random-effects model that allows for enhanced specifications and estimations. METHODS: Longitudinal data from a birth cohort in Mexico (n=586) were used to estimate growth trajectories over 0-24 months for body mass index (BMI), length and weight using the SuperImposition by Translation and Rotation (SITAR) models. The SITAR models use a nonlinear random-effects model to estimate an average growth curve for BMI, length and weight and each participant's deviation from this curve on three dimensions-size, velocity and timing of peak velocity. We used logistic regression to estimate the association between overweight status at 7-9 years and size, velocity and timing of BMI, length and weight trajectories during 0-24 months. We tested whether any association between velocity and overweight varied by relative size during 0-24 months or birth weight. RESULTS: SITAR models explained the majority of the variance in BMI (73%), height (86%) and weight (85%) between 0-24 months. When analyzed individually, relative BMI/length/weight (size) and BMI/length/weight velocity during 0-24 months were each associated with increased odds of overweight in late childhood. Associations for timing of peak velocity varied by anthropometric measure. However, in the mutually adjusted models, only relative BMI/length/weight (size) remained statistically significant. We found no evidence that any association between velocity and overweight varied by size during 0-24 months or birth weight. CONCLUSIONS: After mutual adjustment, size during 0-24 months of life (as opposed to birth size), but not velocity or timing of peak velocity, was most consistently associated with overweight in later childhood.

Estimating the potential impacts of intervention from observational data: methods for estimating causal attributable risk in a cross-sectional analysis of depressive symptoms in Latin America.

BACKGROUND: The field of epidemiology struggles both with enhancing causal inference in observational studies and providing useful information for policy makers and public health workers focusing on interventions. Population intervention models, analogous to population attributable fractions, estimate the causal impact of interventions in a population, and are one option for understanding the relative importance of various risk factors. With population intervention parameters, risk factors are effectively standardised, allowing one to compare their values directly and determine which potential intervention may have the greatest impact on the outcome. METHODS: The difference between total effects and population intervention parameters was examined using naïve, G-computation and inverse probability of treatment weighting approaches. The differences between these parameters and the intuitions they provide were explored using data from a 2003 cross-sectional study in rural Mexico. RESULTS: The assumptions, specific analytic steps, limitations and interpretations of the total effects and population intervention parameters are discussed, and code is provided in Stata. CONCLUSION: Population intervention parameters are a valuable and straightforward approach in epidemiological studies for making causal inference from the data while also supplying information that is relevant for researchers, public health practitioners and policy makers.

Social and economic correlates of depressive symptoms and perceived stress in South African adults.

OBJECTIVES: Adults in South Africa demonstrate rates of mental illness at or above levels elsewhere in the developing world. Yet there is a research gap regarding the social context surrounding mental health in this region. The objective of this analysis was to characterize the prevalence and correlates of depressive symptoms and perceived stress among a heterogeneous South African population. METHODS: Low-income adults (n = 257) in Capetown, Port Elizabeth and Durban were interviewed regarding demographics, income, subjective social status, life events and decision-making. The Center for Epidemiologic Studies Depression Scale (CES-D) and Cohen's Perceived Stress Scale (PSS) were used. RESULTS: CES-D scores were 18.8 (SD 11.7), with 50.4% of men and 64.5% of women exceeding the cut-off at which professional care is recommended (p = 0.03). PSS scores were 18.6 (SD 6.7), with a mean of 17.5 among men and 19.6 among women (p = 0.02). In multivariate regressions, increased CES-D scores were associated with more household members (p<0.1), lower educational attainment (p = 0.07), less income stability (p<0.07), lower subjective social status (p<0.01) and independent decision-making (p = 0.04). Increased PSS scores were associated with female gender (p<0.05), multiracial race (p<0.02), more household members (p<0.1), lower subjective social status (p<0.02) and recent birth or catastrophe (p<0.01). CONCLUSIONS: Depressive symptoms and perceived stress are public health concerns in this sample, with more symptoms among those with fewer resources. The prevention of mental illness is critical, especially in vulnerable populations.

Blood pressure and socioeconomic status in low-income women in Mexico: a reverse gradient?

OBJECTIVES: In the developed world, there is a well-established inverse association between socioeconomic status (SES) and blood pressure. In the developing world, however, these relationships are not as clear, particularly in middle-income countries undergoing epidemiological and nutritional transition. METHODS: A house-to-house cross-sectional survey was conducted in low-income regions of rural Mexico in 2003. A sample of women (n = 9362) aged 18-65 years (mean 35.2, SD 10.4) was assessed. Measurements of systolic blood pressure (SBP) and body mass index (BMI) were obtained using standardised techniques and equipment. Interviews were conducted to collect information about SES, both objective (education, income, housing and assets, occupation) and subjective (perceived social status). RESULTS: Household income, housing and assets were positively and strongly associated with age-adjusted SBP; the associations were attenuated somewhat with the inclusion of BMI. SBP was also positively associated with perceived social status within one's community. In contrast, age and BMI-adjusted SBP was negatively associated with educational achievement. There was a significant education by BMI interaction; at equivalent values for BMI, women who had received at least some secondary education had lower SBP than those who had received less education. CONCLUSIONS: In contrast to traditional assumptions about the associations between SES and health, women in low-income rural populations who are at the upper end of the income spectrum within their community were found to be more likely to have higher SBP, as were those who perceived that they had higher status in the community. These results challenge standard assumptions about the association of SES and health.

Overweight with concurrent stunting in very young children from rural Mexico: prevalence and associated factors.

OBJECTIVE: To document the prevalence of overweight or obesity concurrent with stunting in rural low-income Mexican children and to identify demographic and socio-economic characteristics that could help identify families at risk of having an overweight/obese and stunted young child in this population. DESIGN: Cross-sectional analysis of the nutritional status of very young children, using primary data from a rural community-based survey conducted in 2003. Overweight, obesity and stunting were documented along with several maternal, household and community characteristics. SETTING: Impoverished areas of rural Mexico. SUBJECTS: Pre-school children (n=7555), aged 24-72 months. RESULTS: The combined prevalence of overweight and obesity was equal to or greater than 20% in all children, as was the prevalence of stunting. The prevalence of concurrent overweight or obesity and stunting was approximately 5% in non-indigenous children, and over 10% in indigenous children 24-60 months. A multinomial logistic analysis revealed that the factors associated with coexisting stunting and overweight/obesity were lower socio-economic status (SES), lower maternal age, education, intelligence (vocabulary) and perceived social status, shorter maternal height, and larger household size. Among only stunted children, the risk of also being overweight or obese was associated with younger maternal age (relative risk ratios (RRR): 0.98, P=0.05), lower maternal perceived social status (RRR: 0.95, P<0.01) and maternal obesity (RRR: 2.93, P<0.0001) or overweight (RRR: 1.50, P=0.002). CONCLUSIONS: These analyses highlight that concurrent overweight or obesity and stunting is an important public health issue in low-income areas of rural Mexico beginning in early childhood. Even within this impoverished population, children living in households with low relative SES are the most vulnerable. SPONSORSHIP: Financial support for this research was provided by the National Institutes of Child Health and Human Development, the Fogarty International Center at NIH, the John D and Catherine T MacArthur Foundation 'Research Network on Socioeconomic Status and Health' and the Mexican Government.

Salivary cortisol and heart rate in stunted and nonstunted Nepalese school children.

OBJECTIVE: To test the hypothesis that stunted Nepalese children have an altered stress response system when compared with matched nonstunted children in response to a battery of psychological tests. DESIGN: Case-control study. SETTING: Poor urban areas of Kathmandu, Nepal. SUBJECTS: A total of 64 stunted (less than -2 s.d. height-for-age) children compared with 64 nonstunted (> -1s.d. height-for-age) schoolchildren between 8 and 10 y old matched for school and sex. METHODS: A psychological test session was administered, which included mental arithmetic and two tests of working memory. Salivary cortisol samples were obtained at five points during testing, and heart rate was measured during testing and also at baseline. Salivary cortisol samples were also obtained once early in the morning. Hemoglobin was assessed at the testing session, and extensive data were obtained on the social background of the children's families. RESULTS: Stunted Nepalese children showed a blunted physiologic response (salivary cortisol and heart rate) to psychological stressors (P<0.05) when compared with nonstunted children, but were not different from the nonstunted children in baseline measures, when controlling for social background. The two groups were not different in terms of social background. CONCLUSIONS: These findings suggest that childhood growth retardation may be associated with changes in physiological arousal, and that stunting could be associated with hyporesponsivity in response to psychological stress.

Stress response in school-age children who have been growth retarded since early childhood.

BACKGROUND: Approximately 39% of children aged <5 y in developing countries are growth retarded (stunted) and many have poor mental development and behavioral abnormalities. Animal research suggests that an altered stress response may contribute to the negative outcomes following undernutrition. OBJECTIVE: We tested the hypothesis that stunted children have higher salivary cortisol concentrations and heart rates and altered behavior when compared with nonstunted children when social background was controlled for. DESIGN: We compared 30 stunted with 24 nonstunted children, all of whom were 8-10 y old and lived in the same poor areas of Kingston, Jamaica. All subjects were participants in a prospective, longitudinal, case-control study of children who were stunted in early childhood. We administered a test session (including psychologic and physical stressors), measured baseline and response levels of salivary cortisol and heart rate, and observed behavior. RESULTS: Compared with nonstunted children, stunted children had higher salivary cortisol concentrations (P = 0.007), had higher heart rates during the psychologic test session (P = 0.03), exhibited enhanced cardiovascular responsivity to a physical stressor (P = 0.04), vocalized less, were more inhibited, and were less attentive. After birth weight or social background and maternal and child intelligence quotients were controlled for, the differences in cortisol concentration and cardiovascular reactivity remained significant. CONCLUSIONS: Our findings suggest that consistent growth retardation since early childhood affects physiologic arousal, which, we speculate, may contribute to the poor cognitive functioning and immune responses of stunted children and the relation between adult short stature and increased cardiovascular risk.

Aggressive behaviour in children and adolescents. Part 1: a review of the effects of child and family characteristics

Interpersonal violence is a major public health concern throughout the West Indies, particularly in Jamaica. Many factors contribute to a youth's violent or aggressive behaviour, ranging from individual temperamemt, to family structure, to large sociocultural influences. In Part 1. we review the incidence and severity of violence, and discuss the effects of individual characteristics, and of family structure and discipline. In Part 11, the reported effects of school structure, peer relationships and interaction, corporal punishment and the media on violenct behaviour in children and adolescents are reviewed, and potential policy implication are discussed.(AU)

Aggressive behaviour in children and adolescents. Part I: A review of the effects of child and family characteristics

Interpersonal violence is a major public health concern throughout the West Indies, particularly in Jamaica. Many factors contribute to a youth's violent or aggressive behaviour, ranging from individual temperament, to family structure, to large sociocultural influences. In Part I, we review the incidence and severity of violence, and discuss the effects of individual characteristics, and of family structure and discipline. In Part II, the reported effects of school structure, peer relationships and interaction, corporal punishment and the media on violent behaviour in children and adolescents are reviewed, and potential policy implications are discussed.

Nutritional deficiencies and subsequent effects on mental and behavioral development in children.

Nutritional deficiencies at all stages of growth, both pre- and post-natal, can affect a child's physical, mental and behavioral development. In this paper, we review literature about how mental development is affected by the following nutritional conditions: low birth weight, mild, moderate, and severe protein-energy malnutrition, iodine deficiency, and iron deficiency.

Aggressive behaviour in children and adolescents. Part I: A review of the effects of child and family characteristics.

Interpersonal violence is a major public health concern throughout the West Indies, particularly in Jamaica. Many factors contribute to a youth's violent or aggressive behaviour, ranging from individual temperament, to family structure, to large sociocultural influences. In Part I, we review the incidence and severity of violence, and discuss the effects of individual characteristics, and of family structure and discipline. In Part II, the reported effects of school structure, peer relationships and interaction, corporal punishment and the media on violent behaviour in children and adolescents are reviewed, and potential policy implications are discussed.