Socio-economic position and coronary heart disease risk factors in youth. Findings from the Young Hearts Project in Northern Ireland

Socioeconomic inequalities in childhood-to-adulthood BMI tracking in three British birth cohorts

BACKGROUND

Body mass index (BMI) tracks from childhood-to-adulthood, but the extent to which this relationship varies across the distribution and according to socio-economic position (SEP) is unknown. We aimed to address this using data from three British cohort studies.

METHODS

We used data from: 1946 National Survey of Health and Development (NSHD, n = 2470); 1958 National Child Development Study (NCDS, n = 7747); 1970 British Cohort Study (BCS, n = 5323). BMI tracking between 11 and 42 years was estimated using quantile regression, with estimates reflecting correlation coefficients. SEP disparities in tracking were investigated using a derived SEP variable based on parental education reported in childhood. This SEP variable was then interacted with the 11-year BMI z-score.

RESULTS

In each cohort and sex, tracking was stronger at the upper end of the distribution of BMI at 42 years. For example, for men in the 1946 NSHD, the tracking estimate at the 10th quantile was 0.31 (0.20, 0.41), increasing to 0.71 (0.61, 0.82) at the 90th quantile. We observed no strong evidence of SEP inequalities in tracking in men in the 1946 and 1958 cohorts. In the 1970 cohort, however, we observed tentative evidence of stronger tracking in low SEP groups, particularly in women and at the higher end of the BMI distribution. For example, women in the 1970 cohort from low SEP backgrounds had tracking coefficients at the 50th, 70th, and 90th quantiles, which were 0.05 (-0.04; 0.15), 0.19 (0.06; 0.31), and 0.22 (0.02; 0.43) units higher, respectively, than children from high SEP groups.

CONCLUSION

Tracking was consistently stronger at the higher quantiles of the BMI distribution. We observed suggestive evidence for a pattern of greater BMI tracking in lower (compared to higher) SEP groups in the more recently born cohort, particularly in women and at the higher end of the BMI distribution.

Gestational Age and Cardiorespiratory Fitness in Individuals Born At Term: A Life Course Study

Background

In contrast to the effects of preterm birth, the extent to which shorter gestational age affects the cardiorespiratory fitness (CRF) levels of individuals who were born at term (ie, between 37 and 42 weeks) is largely unknown. The aim of this study was to examine whether life‐course CRF levels varied across different gestational ages within the at‐term range.

Methods and Results

The association between gestational age (in weeks) obtained from Child Health Services records and CRF, estimated from field and laboratory tests and expressed by maximal oxygen uptake level through adolescence to young adulthood, was examined in 791 participants in the Northern Ireland Young Hearts Study, all singletons born at term. Longitudinal data were analyzed with generalized estimating equations, accounting for important potential confounders. Mean levels of CRF were 45.6, 43.7, and 33.0 mL/kg per minute when participants were aged 12, 15, and 22 years, respectively. After adjustment for confounders, each week increase in gestational age was associated with 0.46 mL/kg per minute (95% confidence interval, 0.14–0.79) in CRF. Compared with individuals born full term (39–40 weeks, n=533) or late term (41–42 weeks, n=148), those who were born early term (37–38 weeks, n=110) had a higher incidence of poor CRF (risk ratio, 1.57; 95% confidence interval, 1.14–2.16). The changes in CRF through adolescence to young adulthood were similar across groups, with those born early term consistently displaying the lowest CRF.

Conclusions

These findings suggest that early‐term births within the at‐term range are linked to poorer CRF through adolescence to young adulthood, and may have important clinical and public health implications for policies about (avoidable) early‐term deliveries given their recent increasing trends.

How Do Perceptions of Local Neighborhood Relate to Adolescents' Walking and Cycling?

Purpose.

To examine how perceptions of the local neighborhood relate to adolescents' walking and cycling.

Design.

Exploratory cross-sectional study.

Setting.

Birth cohort from the Nepean Hospital, Sydney, Australia.

Subjects.

Three hundred forty-seven adolescents (79.1% response rate; 49.6% boys; mean age = 13.0 ± 0.2 years) and their parents.

Measures.

Self-report and parental-report questionnaires.

Results.

Multiple linear regressions, adjusted for level of maternal education, revealed that boys who reported having many peers to hang out with locally, cycled for recreation (β = 0.242, p = .006) or for transport (β = 0.141, p = .046) more often, and walked for transport for longer (β = 0.129, p = .024) on weekdays. For girls this variable was related to cycling for recreation on weekends (β = 0.164, p = .006) and walking to school (β = 0.118, p = .002). Adolescents who waved/talked to neighbors walked for transport more often (boys, β = 0.149, p = .037; girls, β = 0.119, p = .012). Girls who perceived local roads to be safe spent more time walking for transport on weekdays (β = 0.183, p = .007) and for exercise on weekends (β = 0.184, p = .034). Parents' perception of heavy traffic was negatively associated with boys' walking for transport (β = −0.138, p = .037) and many aspects of girls' walking and cycling.

Conclusion.

Social interaction and road safety may be important predictors of adolescents' walking and cycling in their neighborhood. Limitations are the use of self-report and cross-sectional data. Longitudinal studies may clarify these relations.

Socioeconomic position and childhood-adolescent weight status in rich countries: a systematic review, 1990-2013

Background

Childhood obesity is a major problem in rich countries due to its high prevalence and its harmful health consequences. An exploratory analysis conducted in the PubMed database highlighted that the number of papers published on the relationship between socioeconomic position (SEP) and childhood-adolescent weight status had risen substantially with respect to an earlier review which had covered the period 1990–2005.

Methods

To describe the findings on the relationship between SEP and childhood-adolescent weight status in papers published in rich countries from 1990 through 2013, studies were identified in the following databases: PubMed; Web of Knowledge (WOK); PsycINFO; Global Health; and Embase. We included observational studies from the 27 richest OECD countries, which covered study populations aged 0 to 21 years, and used parental education, income and/or occupation as family SEP indicators. A total of 158 papers met the inclusion criteria and reported 134 bivariable and 90 multivariable analyses.

Results

Examination of the results yielded by the bivariable analyses showed that 60.4 % of studies found an inverse relationship, 18.7 % of studies did not found relationship, and 20.9 % of studies found a relationship that varied depending on another variable, such as age, sex or ethnic group; the corresponding percentages in the multivariable analyses were 51.1, 20.0 and 27.8 %, respectively. Furthermore, 1.1 % found a positive relationship.

Conclusion

The relationship between SEP and childhood-adolescent weight status in rich countries is predominantly inverse and the positive relationship almost has disappeared. The SEP indicator that yields the highest proportion of inverse relationships is parents’ education. The proportion of inverse relationships is higher when the weight status is reported by parents instead using objective measurements.

Electronic supplementary material

The online version of this article (doi:10.1186/s12887-015-0443-3) contains supplementary material, which is available to authorized users.

Socio-economic position and cardiovascular risk in rural Indian adolescents: evidence from the Andhra Pradesh children and parents study (APCAPS)

Objectives

This study examined association between socio-economic position and cardiovascular risk factors in adolescents to investigate whether childhood socio-economic position is a risk factor for future cardiovascular disease, independently of adult behaviours.

Study design and methods

Participants (n = 1128, 46% girls, aged 13–18 years) were members of a birth cohort (Andhra Pradesh Children and Parents Study or APCAPS) established to investigate long-term effects of a pregnancy and childhood nutritional supplementation trial conducted in 29 villages near Hyderabad in South India. Cross-sectional associations between socio-economic position and cardiovascular risk factors were examined using linear regression models.

Results

The mean BMI was 16.7 kg/m² for boys and 17.8 kg/m² for girls. Socio-economic position was positively associated with fat mass index (0.15 kg/m²; 95% CI: 0.05–0.25) and inversely associated with central-peripheral skinfold ratio (−0.04; 95% CI: −0.06 to −0.01) and, in boys, fasting triglycerides (−0.05; 95% CI: −0.09 to −0.01). Association of socio-economic position with other risk factors (blood pressure, arterial stiffness, fasting glucose, insulin and cholesterol) was weak and inconsistent, and did not persist after adjustment for potential confounders, including age, sex, pubertal stage, height, adiposity and nutrition supplementation.

Conclusions

The study thus showed that lower socio-economic position may be associated with greater central adiposity and higher triglyceride levels in these settings. Socio-economic gradient in cardiovascular risk may strengthen in future with later economic and lifestyle changes. Cardiovascular disease prevention strategies should therefore focus on the youth from the low income group.

Cumulative adversity in childhood and emergent risk factors for long-term health

OBJECTIVE

To examine whether and when effects of cumulative adversity in the first 7 years of life are evident in relation to 3 childhood markers of risk for poor adult physical health.

STUDY DESIGN

The study data are from an English birth cohort. Parental reports of 8 social risk factors were obtained during the child's first 7 years, and scores were created to reflect cumulative adversity at 4 developmental periods. At age 7 and 11 years, weight, height, and blood pressure (BP) were measured by clinic staff, and caregivers reported behavior problems. Linear regression was used to estimate associations of cumulative adversity with each outcome (n = 4361) and changes in these outcomes between 7 and 11 years (n = 3348).

RESULTS

At age 7 years, mean adversity and chronic exposure to high adversity were associated with elevated body mass index (BMI) and internalizing and externalizing symptoms (P < .05), but not elevated BP. Adversity in all developmental periods was associated with elevated numbers of internalizing and externalizing symptoms (P < .0001), but associations were less robust for BMI. Adversity did not predict change in BMI or BP between age 7 and 11 years, however, it predicted increases in internalizing and externalizing symptoms (P < .0001).

CONCLUSION

Cumulative adversity was associated with BMI and behavior problems at age 7 years, and our data indicate that timing and chronicity of exposure to adversity differentially influence diverse indicators of long-term health risk commonly measured in childhood. This research suggests the hypothesis that interventions to address adversity could reduce the development of multiple chronic disease risk factors and limit their effects on health.

The impact of family and parental education on adolescents' substance use: a study of U.S. high school seniors

This study explores the impact of family structure and parental education on adolescents' substance use using a racially diverse sample of 14,268, 12th-grade high school adolescents. Findings reveal that family structure affects adolescents' substance use. In addition, racial differences are noted. African American adolescents report a relatively lower rate of substance use compared to White and Hispanic adolescents, yet they are gravely affected by substance use outcomes. The study lends further support that family structure and parental education variables may buffer adolescents from substance abuse influences. Implications for practice and policy are discussed.

Acute ingestion of beetroot bread increases endothelium-independent vasodilation and lowers diastolic blood pressure in healthy men: a randomized controlled trial

Dietary nitrate, from beetroot, has been reported to lower blood pressure (BP) by the sequential reduction of nitrate to nitrite and further to NO in the circulation. However, the impact of beetroot on microvascular vasodilation and arterial stiffness is unknown. In addition, beetroot is consumed by only 4.5% of the UK population, whereas bread is a staple component of the diet. Thus, we investigated the acute effects of beetroot bread (BB) on microvascular vasodilation, arterial stiffness, and BP in healthy participants. Twenty-three healthy men received 200 g bread containing 100 g beetroot (1.1 mmol nitrate) or 200 g control white bread (CB; 0 g beetroot, 0.01 mmol nitrate) in an acute, randomized, open-label, controlled crossover trial. The primary outcome was postprandial microvascular vasodilation measured by laser Doppler iontophoresis and the secondary outcomes were arterial stiffness measured by Pulse Wave Analysis and Velocity and ambulatory BP measured at regular intervals for a total period of 6 h. Plasma nitrate and nitrite were measured at regular intervals for a total period of 7 h. The incremental area under the curve (0-6 h after ingestion of bread) for endothelium-independent vasodilation was greater (P = 0.017) and lower for diastolic BP (DBP; P = 0.032) but not systolic (P = 0.99) BP after BB compared with CB. These effects occurred in conjunction with increases in plasma and urinary nitrate (P < 0.0001) and nitrite (P < 0.001). BB acutely increased endothelium-independent vasodilation and decreased DBP. Therefore, enriching bread with beetroot may be a suitable vehicle to increase intakes of cardioprotective beetroot in the diet and may provide new therapeutic perspectives in the management of hypertension.

Socioeconomic and other social stressors and biomarkers of cardiometabolic risk in youth: a systematic review of less studied risk factors

Background

Socioeconomic disadvantage and other social stressors in childhood have been linked with cardiometabolic diseases in adulthood; however the mechanisms underlying these observed associations and the timing of their emergence are unclear. The aim of this review was to evaluate research that examined relationships between socioeconomic disadvantage and other social stressors in relation to less-studied cardiometabolic risk factors among youth, including carbohydrate metabolism-related factors, lipids, and central adiposity.

Methods

We searched PubMed and ISI Web of Science to identify relevant publications between 2001 and 2013.Studies were selected based on 4 criteria: (1) the study examined an association between at least one social or economic stressor and one relevant outcome prior to age 21; (2) the sample originated from a high-income country; (3) the sample was not selected based on a health condition; and (4) a central aim was to evaluate the effect of the social or economic stressor on at least one relevant outcome. Abstracts were screened and relevant publications were obtained and evaluated for inclusion criteria. We abstracted data from selected articles, summarized them by exposures and outcomes, and assigned an evidence grade.

Results

Our search identified 37 publications from 31 studies. Socioeconomic disadvantage was consistently associated with greater central adiposity. Research to date does not provide clear evidence of an association between childhood stressors and lipids or carbohydrate metabolism-related factors.

Conclusions

This review demonstrates a paucity of research on the relationship of socioeconomic disadvantage and other social stressors to lipid and carbohydrate metabolism-related factors in youth. Accordingly, it is not possible to form strong conclusions, particularly with regard to stressors other than socioeconomic disadvantage. Findings are used to inform priorities for future research. An improved understanding of these pathways is critical for identifying novel prevention targets and intervention opportunities to protect the long-term health of children and adolescents.

Family- and school-based predictors of energy balance-related behaviours in children: a 6-year longitudinal study

OBJECTIVE

To examine family- and school-based predictors of breakfast consumption, soft drink consumption and physical activity (PA) and moderating effects of gender and socio-economic status (SES).

DESIGN

Longitudinal study (6-year follow-up), including a questionnaire about dietary and activity behaviour.

SETTING

Fifty-nine Flemish elementary schools.

SUBJECTS

Seven hundred and twenty-seven children (51·9 % girls, 51·9 % high SES, mean age 9·9 (sd 0·4) years at baseline).

RESULTS

Having breakfast together with parents (P < 0·001) at age 10 years related to more days of eating breakfast at age 16 years. More parental soft drink consumption (P = 0·04), less soft drink availability at home (P < 0·001) and less parental permissiveness (children received soft drinks from their parents whenever they asked for it and children could take soft drinks whenever they wanted; P = 0·02 and P = 0·001, respectively) at age 10 years related to less soft drink consumption at age 16 years. A more positive parental attitude towards PA (P = 0·009), more parental encouragement (P = 0·002) and a higher rating of PA's benefit 'relaxing' (P < 0·001) at age 10 years related to more PA at age 16 years. Gender and SES did not significantly moderate any of the associations.

CONCLUSIONS

Only parental factors at age 10 years were associated with breakfast consumption, soft drink consumption and PA at age 16 years. An intervention programme at age 10 years with a strong focus on the modifiable parental factors might lead to healthy behaviour in the long term.

Socioeconomic inequalities in lipid and glucose metabolism in early childhood in a population-based cohort: the ABCD-Study

Background

Socioeconomic inequalities in cardiovascular disease are pervasive, yet much remains to be understood about how they originate. The objective of this study was to explore the relations of socioeconomic status to lipid and glucose metabolism as indicators of cardiovascular health in 5–6 year olds. Additionally to explore the explanatory role of maternal factors, birth outcome, and child factors.

Methods

In 1308 5–6 year old ethnic Dutch children from the ABCD cohort study, lipids (cholesterol, LDL, HDL, triglycerides), glucose and C-peptide were measured after an overnight-fast.

Results

There were no differences in cholesterol, HDL, LDL, and triglycerides between socioeconomic groups, as indicated by maternal education and income adequacy. However, children of low educated mothers had on average a higher glucose (β = 0.15; 95% confidence interval (CI) 0.03 – 0.27), logC-peptide (β = 0.07; 95% CI 0.04 – 0.09), and calculated insulin resistance (HOMA-IR) (β = 0.15; 95% CI 0.08 – 0.22) compared to children of high educated mothers. Only childhood BMI partly explained these differences (models controlled for age, height, and sex).

Conclusions

The socioeconomic gradient in cardiovascular risk factors seems to emerge in early childhood. In absence of underlying mechanisms these empirical findings are relevant for public health care and further explanatory research.

The social network, socioeconomic background, and school type of adolescent smokers

The aim of this study is to examine the role of Dutch second grade (age 13–14) high school peer networks in mediating socioeconomic background and school type effects on smoking behavior. This study is based on a longitudinal design with two measurement waves at five different high schools, of the complete networks of second grader friendships, as well as their smoking behavior, school type, and parents’ educational level. The analysis is done by simulation investigation for empirical network analysis (SIENA) modeling that can control for friendship selection on the basis of smoking similarity when assessing friends’ influence on smoking. The findings show that, when controlling for friendship selection, the influence of friends still plays a significant role in adolescent smoking behavior, and suggests that socioeconomic background and school type effects on smoking are mediated by the friendship networks at school.

Prevalence of traditional and novel markers of cardiovascular disease risk in Scottish adolescents: socioeconomic effects

Information on the health status and physical activity of Scottish adolescents is limited. This study examines the prevalence of cardiovascular disease (CVD) risk in Scottish adolescents by socioeconomic status (SES). Participants were recruited from two high schools that differed in the SES of the students in attendance. The sample included 73 boys and 34 girls (16.4 ± 0.6 years). Variables included anthropometry, physical activity, physical fitness, blood pressure, diet, and 11 metabolic markers of CVD risk. Significant sex differences (P ≤ 0.01) were noted for stature, waist circumference, waist-hip ratio, physical activity, cardiorespiratory fitness, muscular power, sprint speed, and several CVD risk factors: high-density lipoprotein (HDL), low-density lipoprotein (LDL), interleukin-6 (IL-6), and C-reactive protein (CRP) levels. Boys from a lower SES had significantly higher levels of glucose and plasminogen activator inhibitor-1 (PAI-1) but lower levels of adiponectin compared with boys from a higher SES. Girls from a lower SES had significantly (P ≤ 0.01) higher glucose and PAI-1 levels but lower levels of insulin and adiponectin than girls from a higher SES. High fat diets, low physical activity levels, and elevated CRP and total cholesterol levels were the CVD risk factors most commonly identified as being at-risk levels in this cohort, regardless of sex or SES. SES differences were not consistently apparent, but several CVD risk factors were identified as elevated in this sample of adolescents, regardless of sex or SES.

Household income, food insecurity and nutrition in Canadian youth

OBJECTIVE

The contribution of nutrition to health inequalities is poorly understood, particularly with regard to children. The objective of this study was to examine the influence of income and the conjoint influence of low income and food insecurity on several dietary indicators in a representative sample of Canadian youth.

METHODS

We used data from the Canadian Community Health Survey (CCHS) Cycle 2.2, a nationally representative population-based sample, to examine the diets of 8,938 youth aged 9-18 years. A single 24-hour recall was used to collect dietary information. Interviews were conducted in person, and anthropometric measurements were available for 71% of the sample. Estimates of variance were calculated using bootvar with weights specific to the CCHS. Generalized linear models were used to examine the associations between both low income and low-income food insecurity and anthropometric measures, food and nutrient intakes.

RESULTS

Youth from low-income households had lower height percentiles than youth from higher-income households. Low-income girls (but not low-income boys) had a higher prevalence of BMI > or = 85th percentile than their higher-income counterparts. Among low-income food-insecure households, there was a higher prevalence of BMI > or = 85th percentile in boys than among the food-secure low-income boys. Calcium and vitamin D intakes were lower among boys and girls living in low-income households. Similarly, milk consumption was lower in low-income boys. Low-income food-insecure girls had lower milk intakes and higher intake of sweetened beverages.

CONCLUSIONS

We found some evidence of nutritional deprivation among Canadian youth from disadvantaged households. Longer-term indicators of nutritional status such as lower height and greater weight among disadvantaged households were consistent with these findings.

Family- and school-based correlates of energy balance-related behaviours in 10-12-year-old children: a systematic review within the ENERGY (EuropeaN Energy balance Research to prevent excessive weight Gain among Youth) project

OBJECTIVE

To identify family- and school-based correlates of specific energy balance-related behaviours (physical activity, sedentary behaviour, breakfast consumption, soft drink consumption) among 10-12-year-olds, using the EnRG framework (Environmental Research framework for weight Gain prevention).

DESIGN

A literature review to identify observational studies exploring at least one family- or school-based correlate of the specific behaviours, resulting in seventy-six articles.

SETTING

Eighteen studies were conducted in Europe, forty-one studies in North America and seventeen studies in Australasia.

SUBJECTS

Healthy children aged 10-12 years.

RESULTS

Parental and maternal physical activity, doing physical activities with parents and parental logistic support were identified as the most important, positive correlates of physical activity. Parental rules was the most important correlate of sedentary behaviour and was inversely related to it. School socio-economic status was positively related to physical activity and inversely related to sedentary behaviour. The available studies suggested a positive relationship between soft drink availability at home and consumption. Soft drink availability and consumption at school were the most important school-based correlates of soft drink consumption. A permissive parenting style was related to more soft drink consumption and less breakfast consumption.

CONCLUSIONS

An important role has been awarded to parents, suggesting parents should be involved in obesity prevention programmes. Despite the opportunities a school can offer, little research has been done to identify school-environmental correlates of energy balance-related behaviours in this age group. Obesity prevention programmes can focus on the most important correlates to maximize the effectiveness of the programme. Future research should aim at longitudinal studies.

Inflammation markers are associated with cardiovascular diseases risk in adolescents: the Young Hearts project 2000

PURPOSE

The traditional approach for identifying subjects at risk from cardiovascular diseases (CVD) is to determine the extent of clustering of biological risk factors adjusted for lifestyle. Recently, markers of endothelial dysfunction and low grade inflammation, including high sensitivity C-reactive protein (hsCRP), soluble intercellular adhesion molecules (sICAM), and soluble vascular adhesion molecules (sVCAM), have been included in the detection for high risk individuals. However, the relationship of these novel biomarkers with CVD risk in adolescents remains unclear. The purpose of this study, therefore, was to establish the association of hsCRP, sICAM, and sVCAM with CVD risk in an adolescent population.

METHODS

Data from the Young Hearts 2000 cross-sectional cohort study, carried out in 1999-2001, were used. From a total of 2,017 male and female participants, 95 obese subjects were identified and matched according to age, sex, and cigarette smoking, with 95 overweight and 95 normal-weight adolescents. Clustered CVD risk was computed using a sum of Z-scores of biological risk factors. The relationship was described using multiple linear regression analyses.

RESULTS

hsCRP, sICAM, and sVCAM showed significant associations with CVD risk. hsCRP and sICAM had a positive relation with CVD risk, whereas sVCAM showed an inverse relationship. In this study, lifestyle factors showed no relation with CVD risk.

CONCLUSION

The results fit the hypothesized role of low grade inflammation and endothelial dysfunction in CVD risk in asymptomatic adolescents. The inverse relationship of VCAM, however, is hard to explain and indicates the complex mechanisms underlying CVD. Further research is needed to draw firm conclusions on the biomarkers used.

Are there socioeconomic inequalities in cardiovascular risk factors in childhood, and are they mediated by adiposity? Findings from a prospective cohort study

BACKGROUND

Socioeconomic gradients in adiposity were not present during childhood for previous generations, but have emerged in contemporary children. It is unknown whether this translates to socioeconomic gradients in associated cardiovascular risk factors in children, with consequent implications for inequalities in coronary heart disease (CHD) and diabetes when these children reach adulthood.

METHODS

Using data from 7772 participants aged 10-years from the Avon Longitudinal Study of Parents and Children, we examined the association between maternal education and a large number of cardiovascular risk factors (cholesterol, triglycerides, high-density lipoprotein, apolipoprotein, adiponectin, leptin, C-reactive protein (CRP), interleukin-6 (IL-6) and systolic and diastolic blood pressure), and examined whether inequalities were mediated by adiposity, measured by dual energy X-ray absorptiometry (DXA)-assessed total fat mass.

RESULTS

There were socioeconomic differences in a number of the cardiovascular risk factors (apolipoprotein B, systolic and diastolic blood pressure, CRP, leptin and IL-6). Inequalities were greater in girls than boys. Inequalities in CRP and leptin were completely mediated by adiposity. Inequalities in other cardiovascular risk factors were partially mediated by adiposity.

CONCLUSION

This study showed important socioeconomic inequalities in adiposity and associated cardiovascular risk factors in a contemporary UK population of 10-year-old children. Differences between contemporary children and previous generations in the socioeconomic patterning of cardiovascular risk factors suggest future adults may have greater inequalities in diabetes and CHD than current adults. These findings highlight the importance of interventions aimed at preventing obesity in childhood, particularly among those of lower socioeconomic position.

Clustering of multiple lifestyle behaviours and its relationship with weight status and cardiorespiratory fitness in a sample of Flemish 11- to 12-year-olds

Objective

The aim of the present study was to explore the existence of clusters in multiple lifestyle behaviours, including physical activity (PA), sedentariness and food habits, in young adolescents. The present study also investigated whether the identified groups could be characterised by gender and components of health-related physical fitness, especially weight status and cardiorespiratory fitness (CRF).

Design

A cross-sectional survey. Leisure-time PA, sedentary behaviour and food consumption were assessed by a questionnaire. Overweight prevalence was estimated using BMI (kg/m2) calculated from self-reported height and weight. CRF was measured using a 20 m shuttle-run test.

Setting

The study was conducted in four middle schools in Flanders, Belgium.

Subjects

The sample size was 317 seventh grade students aged 11–12 years.

Results

Four reliable and meaningful lifestyle clusters could be identified, labelled as ‘Sporty media-oriented mixed eaters’ (boys:n34; girls:n16), ‘Academic healthy eaters’ (boys:n30; girls:n58), ‘Inactive healthy eaters’ (boys:n38; girls:n57) and ‘Inactive media-oriented unhealthy eaters’ (boys:n35; girls:n49). The lifestyle clusters could not be characterised by adolescents’ weight status. Among boys, the ‘Sporty media-oriented mixed eaters’ group performed significantly better on the shuttle-run test than those in clusters with the lowest levels of PA (clusters 3 and 4).

Conclusions

Our results showed that healthy and risk-related behaviours may coexist in some groups of young adolescents. Isolated unhealthy behaviours, such as high levels of screen-based media use or high consumption of energy-dense food items, are not necessarily related with negative health outcomes, on the condition that these risk-related behaviours co-occur with more health-enhancing behaviours such as PA.

Socio-economic status and oral health-related behaviours in Korean adolescents

The principle objective of this study was to assess the association between socio-economic status (SES) and oral health-related behaviours in Korean adolescents aged 13-18, using the Family Affluence Scale (FAS). The secondary objective was to assess the influences of other factors (pocket money, school type, family structure and psychological factors) on this association. Cross-sectional data were from the national 2007 Korean Youth Risk Behavior Web-based Survey. Oral health-related behaviours included health-enhancing behaviours (frequency of toothbrushing and dental visits) and health-compromising behaviours (smoking and frequency of intake of soft drinks and confections). Logistic regression models were used to analyse the data. To assess the influence of other factors, additional models adjusting for sex, school grade and each of the other factors were compared to the initial model, which adjusted for sex and school grade only. We found that family affluence had a linear association with health-enhancing behaviours and a roughly U-shaped association with health-compromising behaviours. After adjusting for a number of variables, the linear association with health-enhancing behaviours persisted. The U-shaped association with health-compromising behaviours remained but was partly attenuated and flattened. In addition, we found a marked influence of school type and family structure and pocket money on the association between FAS and oral health-compromising behaviours. The findings indicate that the health-enhancing behaviours of adolescents were strongly associated with family affluence, but the health-compromising behaviours were more strongly linked to factors other than family affluence. However, it is difficult to determine which factors contribute most in relation to family affluence because of other confounding factors, such as the education system, peer group, youth culture, part-time work and advertising. Therefore, further studies are needed to assess factors that interact with family SES to better understand the association between the SES and the oral health-compromising behaviours of adolescents.

Inequalities in Croatian pupils' unhealthy behaviours and health outcomes: role of school, peers and family affluence

BACKGROUND

To examine the influence of family affluence (measure of socioeconomic status), school environment (liking school, school pressure, academic achievement and classmates support) and peer group (size of the peer group and frequency of peer contact) on unhealthy behaviours (smoking, drunkenness, physical inactivity, irregular breakfast and soft drink consumption) and health outcomes (self-rated health, multiple health complaints and life satisfaction) in Croatian pupils.

METHODS

The Croatian data from Health Behaviour in School-aged Children 2005/06 (HBSC) were used (1666 11-year-olds, and 1630 15-year-olds). Binary logistic regression analysis was conducted (95% confidence intervals, P < 0.05 and P < 0.01).

RESULTS

School environment and peer group were connected to more unhealthy behaviours along with greater differences in those behaviours than family affluence. The only exception was physical inactivity at age 11 (compared to high family affluence, low family affluence increased 80% odds for physical inactivity, whereas, compared to favourable school environment, poor school environment increased 50% odds). Compared to favourable school environment, poor school environment was the most consistent and strongest predictor of poor health outcomes (all three measures). No influence of peer group to health outcomes was found. Compared to high-affluent families, low-affluent families were associated to higher odds for poor self-rated health and life dissatisfaction, and, for 11-year-olds, medium-affluent families to lower odds for multiple health complaints. Gender differences in unhealthy behaviours and health outcomes were also found.

CONCLUSIONS

Compared to socioeconomic inequalities, greater inequalities in unhealthy behaviours were connected to school environment and peer group, and in health outcomes to school environment.

Social inequality in adolescent daily smoking: has it changed over time?

BACKGROUND AND AIM

In most northern European countries adolescent smoking is most prevalent in lower social classes but there is little information about time trends in social inequality. This paper describes trends in social inequality in daily smoking among adolescents from 1991 to 2006 by both absolute social inequality (prevalence difference between low and high social class) and relative social inequality (prevalence ratio).

METHODS

We analysed 15-year-olds from the Health Behaviour in School-aged Children (HBSC) study in Denmark in 1991, 1994, 1998, 2002 and 2006, total n = 6703. The surveys were comparable because of similar procedures for sampling, data collection, and measurements of smoking and parents' occupational social class.

FINDINGS

From 1991 to 2006 the prevalence of daily smoking decreased from 15.9% to 10.9% among boys and from 20.1% to 10.6% among girls. The social inequality fluctuated over time and was different for boys and for girls. The prevalence difference between boys from low and high social class was 5.2% in 1991 and 9.3% in 2006, corresponding figures for girls were 4.8% and 7.0%. The prevalence ratio among boys was 1.38 (in 1991) and 2.19 (in 2006), among girls 1.28 and 1.95.

CONCLUSIONS

Daily smoking was most prevalent among students from lower social classes and the level of inequality fluctuated over time. Conclusions on social inequality in adolescent smoking may appear differently when described by absolute and relative measures. The absolute and relative social inequality in adolescent smoking was higher in 2006 than in 1991.

Physical fitness and physical activity at age 13 years as predictors of cardiovascular disease risk factors at ages 15, 25, 33, and 40 years: extended follow-up of the Oslo Youth Study

OBJECTIVE

Few studies have examined the association of childhood physical activity and physical fitness with cardiovascular disease risk factors in adulthood. Furthermore, interpretation of these findings is hampered by methodologic shortcomings. In a population-based cohort study, we explored the influence, if any, of childhood physical activity and physical fitness on later cardiovascular disease risk factors.

METHODS

Data were taken from the Oslo Youth Study, a prospective cohort study that began in 1979, when 1016 students (mean age: 13 years; range: 11-15 years) who were attending 6 schools were invited to participate in a health education intervention. Cardiovascular disease risk factor data were collected at baseline and again in 1981 (mean age: 15 years; range: 13-17 years), 1991 (mean age: 25; range: 23-27 years), 1999 (mean age: 33; range: 31-35 years), and 2006 (mean age: 40; range: 38-42 years).

RESULTS

At baseline, physical fitness was inversely related to BMI, triceps skinfold thickness, and blood pressure (systolic and diastolic; N = 716). These associations were also present in prospective analyses at ages 15 (N = 472), 25 (N = 280; except for systolic blood pressure), and 33 years (N = 410, only BMI measured)-albeit with progressively diminishing magnitude-but were lost at 40 years (N = 294). There were fewer relationships with cardiovascular disease risk factors when physical activity was the exposure of interest. Controlling for educational attainment of both the parent and the study member had little impact on these associations.

CONCLUSIONS

Although childhood physical fitness seems to reveal some inverse associations with obesity and blood pressure in early adulthood, these effects diminished markedly into middle age.

Why do parents' education level and income affect the amount of fruits and vegetables adolescents eat?

BACKGROUND

There are large socioeconomic disparities in food behaviours. The objective of the present study is to longitudinally explore socioeconomic disparities in adolescents' fruit and vegetable (FV) intake and to assess mediators of the disparity.

METHODS

A longitudinal study containing 896 adolescents from 20 randomly selected elementary schools within two Norwegian counties (response rate 84%). Questionnaires were administered in May 2002 (mean age 12.5 years) and again in May 2005. FV intake was measured by four food frequency questions (times/week). Socioeconomic status was based on parents' reports of their own educational level and family income (both dichotomized). Data were analysed with repeated mixed models.

RESULTS

A disparity in adolescents' FV intake was observed with family income (1.1 times/week, P = 0.05). An interaction between parental education and time (survey) was found for parental education (P = 0.04) and the educational disparity was greater in 2005 (2.4 times/week, P < 0.001) than in 2002 (1.3 times/week, P = 0.03). In multiple mediation analyses, a total of 92% (2002) and 60% (2005) of the educational disparity and 89% of the income disparity, were explained. For both, the adolescents' reports of the accessibility of FV at home explained most of the disparity.

CONCLUSIONS

Perceived accessibility appears to be the strongest mediator of the relationship between adolescents' FV intake and their parents' educational level and income and may therefore be an important target for future interventions that aim to reduce socioeconomic disparities in adolescents' FV intake.

Socioeconomic status and adiposity in childhood: a systematic review of cross-sectional studies 1990-2005

BACKGROUND

Sobal and Stunkard's review (1989) of 34 studies from developed countries published after 1941, found inconsistent relationships between socioeconomic status (SES) and childhood adiposity. Inverse associations (36%), no associations (38%), and positive associations (26%) were found in similar proportions. In view of the trends in pediatric obesity, the relationship between SES and adiposity may have changed.

OBJECTIVE

To describe the cross-sectional association between SES and adiposity in school-age children from western developed countries in epidemiological studies since 1989.

METHODS AND PROCEDURES

PubMed database was searched to identify potentially relevant publications. Epidemiological studies from western developed countries presenting cross-sectional data on the bivariate association between an SES indicator and objectively measured adiposity in childhood (5-18 years), carried out after 1989 were included. SES indicators included parental education, parental occupation, family income, composite SES, and neighborhood SES.

RESULTS

Forty-five studies satisfied the review criteria. SES was inversely associated with adiposity in 19 studies (42%), there was no association in 12 studies (27%), and in 14 studies (31%) there was a mixture of no associations and inverse associations across subgroups. No positive SES-adiposity associations were seen in unadjusted analyses. With parental education as the SES indicator, inverse associations with adiposity were found in 15 of 20 studies (75%).

DISCUSSION

Research carried out within the past 15 years finds that associations between SES and adiposity in children are predominately inverse, and positive associations have all but disappeared. Research is needed to understand the mechanisms through which parental social class influences childhood adiposity.

Socioeconomic position and the metabolic syndrome in early, middle, and late life: evidence from NHANES 1999-2002

PURPOSE

To evaluate whether there is an association between socioeconomic position (SEP) and the metabolic syndrome at various ages, including adolescent, middle-aged and older participants in gender-specific analyses.

METHODS

Participants were from the 1999-2002 National Health and Nutrition Examination Survey. SEP was measured by income and years of education. Metabolic syndrome was measured in adults using the American Heart Association guidelines and in adolescents using methods based on national reference data. Cross-sectional multivariable-adjusted logistic regression analyses were performed.

RESULTS

In women aged 25 to 45 and 46 to 65 years, income below the poverty line (poverty income ratio [PIR] less than one) was associated with higher odds of metabolic syndrome compared with PIR greater than 3 (odds ratio [OR] = 4.90; 95% confidence interval (CI) = 2.24, 10.71, and OR = 2.54; CI = 1.38, 4.67, for the respective age groups) after adjustment for age, race/ethnicity, and menopause. Similar findings were observed for educational attainment. In adolescents, older adults (aged >65 years), and males, income and education were not related to the metabolic syndrome.

CONCLUSIONS

This report demonstrates that SEP is associated with the metabolic syndrome in females aged 25 to 65 years and is less strongly associated in males, adolescents, or older participants. These findings provide physiologic mechanistic evidence linking SEP to risk for coronary heart disease.

Sources of variation in habitual physical activity of children and adolescents: the European youth heart study

The present study examined the influence of gender, maturity state, seasonality, type of measurement day and socioeconomic status (SES) on habitual physical activity in 8-10-year-old children and 14-16-year-old adolescents (n=1318). Physical activity was assessed objectively by accelerometry. The results showed a significant effect of the type of measurement day on physical activity with a general pattern of lower activity levels in weekends compared with weekdays. Furthermore, higher physical activity levels were observed during the months of spring/summer compared with the months of autumn/winter for the 8-10-year-olds, whereas no significant effect of months was observed for the 14-16-year-olds, possibly due to exam preparations and lack of physical activity registration during the months of summer for this cohort. SES was unrelated to physical activity in the 8-10-year-olds, whereas an inverse association was observed in the 14-16-year-olds. However, a post hoc analysis provided strong evidence that this latter result was biased by the accelerometers inability to pick up bicycling activities. Finally, boys were more physically active compared with girls, and maturity state was unrelated to physical activity. The results could prove useful for working out strategies to prevent inactivity and for adjusting for temporal sources of variation in physical activity in future studies.

Trends in socio-economic differences in tobacco smoking among German schoolchildren, 1994-2002

BACKGROUND

While the graded relationship between socio-economic status (SES) and risk behaviour in adulthood has been the subject of intense research, far less is known about socio-economic differences in health-related behaviour among adolescents. The purpose of the present study is to examine socio-economic differences in adolescent tobacco use in Germany as well as changes in the relationship between 1994 and 2002.

METHODS

Data were obtained from the 'Health Behaviour in School-aged Children' study conducted in the largest federal state of Germany, Northrhine-Westfalia, in 1994, 1998 and 2002. The analysis is based on 11.401 11- to 15-year old students. Socio-economic differences in regular smoking were studied in relation to both parental SES (family affluence) and students own SES (school type). Trends from 1994 to 2002 were analysed for each category of family affluence and school type separately.

RESULTS

Family affluence only had a weak effect on regular smoking while for type of school a strong social gradient for smoking was found for both the genders. Trend analyses within the different family affluence and school-type categories showed that smoking has generally increased in all socio-economic groups. The level of socio-economic differences remained virtually unchanged in girls and boys in the past 10 years in Germany.

CONCLUSIONS

The same relationships of family affluence and school type with smoking have persisted for almost a decade in Germany. Students own SES affects adolescent smoking substantially. Prevention programmes should focus on the school setting in order to tackle current as well as future health inequalities.

The relationship between parental socio-economic status and episodes of drunkenness among adolescents: findings from a cross-national survey

Background

Behavioral factors such as (excessive) alcohol consumption play a major role in the explanation of social inequalities in health. The unequal distribution of health risk behaviors among socio-economic groups has important consequences for both the current and future health status of the younger generation. However, little is known about socio-economic differences in unhealthy lifestyles during adolescence. The purpose of the present study is to investigate socio-economic differences in adolescent drinking behaviour among 11–15 year old adolescents in Europe and North America.

Methods

Data was obtained from the Health Behaviour in School-aged Children (HBSC) study 2001/02, a cross-national survey conducted in collaboration with the World Health Organization. The present analysis is based on 69249 male and 73619 female students from 28 countries. The effect of parental occupation and family affluence on episodes of drunkenness was assessed using separate logistic regression models controlling for age.

Results

Socio-economic circumstances of the family had only a limited effect on repeated drunkenness in adolescence. For girls only in one out of 28 countries a significant association between family affluence and repeated drunkenness was observed, while boys from low and/or medium affluent families in nine countries faced a lower risk of drunkenness than boys from more affluent families. Regarding parental occupation, significant differences in episodes of drunkenness were found in nine countries for boys and in six countries for girls. Compared to family affluence, which was positively related to risk of drunkenness, a decreasing occupational status predicted an increasing risk of drunkenness. This pattern was identified within a number of countries, most noticeably for boys.

Conclusion

Parental socio-economic status is only of limited importance for episodes of drunkenness in early adolescence, and this very limited role seems to apply for girls more than for boys and for parental occupation more than family affluence. For future studies it might be important to look at the effects of socio-economic status within the context of other peer, family and school related factors in order to assess to what extent those factors might mediate the effects of social class background.

Determinants of fruit and vegetable consumption among children and adolescents: a review of the literature. Part I: Quantitative studies

BACKGROUND

In order to more effectively promote fruit and vegetable intake among children and adolescents, insight into determinants of intake is necessary. We conducted a review of the literature for potential determinants of fruit and vegetable intake in children and adolescents.

METHODS

Papers were identified from Medline and PsycINFO by using all combinations of the search terms: "fruit(s) or vegetable(s)" and "children or adolescents". Quantitative research examining determinants of fruit and/or vegetable intake among children and adolescents aged 6-18 years were included. The selection and review process was conducted according to a four-step protocol resulting in information on country, population, design, methodology, theoretical basis, instrument used for measuring intake, statistical analysis, included independent variables, and effect sizes.

RESULTS

Ninety-eight papers were included. A large number of potential determinants have been studied among children and adolescents. However, for many presumed determinants convincing evidence is lacking, mostly because of paucity of studies. The determinants best supported by evidence are: age, gender, socio-economic position, preferences, parental intake, and home availability/accessibility. Girls and younger children tend to have a higher or more frequent intake than boys and older children. Socio-economic position, preferences, parental intake, and home availability/accessibility are all consistently positively associated with intake.

CONCLUSION

The determinants most consistently supported by evidence are gender, age, socio-economic position, preferences, parental intake and home availability/accessibility. There is a need for internationally comparative, longitudinal, theory-based and multi-level studies taking both personal and environmental factors into account. This paper is published as part of the special Pro Children series in the International Journal of Behavioral Nutrition and Physical Activity. Please see [http://www.ijbnpa.org/content/3/1/26] for the relevant editorial.

Secular trends in cardiorespiratory fitness and body mass index in Danish children: The European Youth Heart Study

AIM

To examine the secular trends in cardiorespiratory fitness (CF) and body fatness in Danish children. Trends were analyzed overall and across socioeconomic status (SES).

METHODS

Two cross-sectional studies conducted on 589 and 458 third-grade Danish children in 1997-1998 and 2003-2004, respectively. CF was determined by a maximal cycle-ergometer test. The lowest sex-specific quartile of CF in the study from 1997 to 1998 was used as a cut-point for low CF. Body mass index (BMI) cut-points were used to describe overweight, and SES was divided into two groups according to parents' occupation.

RESULTS

This study showed a secular decline in CF in girls overall. Increased CF, BMI, and prevalence of overweight were observed in boys with high SES, in boys with low SES, and in girls with low SES, respectively. However, after additional Bonferroni's correction, none of the statistical analyses performed across socioeconomic gradients reached significant P-values.

CONCLUSION

CF declined in girls overall. Although not statistically significant after additional Bonferroni's correction, results in general showed less favorable trends in low SES children. Thus, trying to describe secular trends in CF and body fatness overall without any regard to SES might disguise social-caused differences. However, further studies are needed in order to verify this hypothesis.

Tracking and prevalence of cardiovascular disease risk factors across socio-economic classes: a longitudinal substudy of the European Youth Heart Study

BACKGROUND

The highest prevalence of several cardiovascular disease risk factors including obesity, smoking and low physical activity level is observed in adults of low socioeconomic status. This study investigates whether tracking of body mass index and physical fitness from childhood to adolescence differs between groups of socioeconomic status. Furthermore the study investigates whether social class differences in the prevalence of overweight and low physical fitness exist or develop within the age range from childhood to adolescence.

METHODS

In all, 384 school children were followed for a period of six years (from third to ninth grade). Physical fitness was determined by a progressive maximal cycle ergometer test and the classification of overweight was based on body mass index cut-points proposed by the International Obesity Task Force. Socioeconomic status was defined according to The International Standard Classification of Occupation scheme.

RESULTS

Moderate and moderately high tracking was observed for physical fitness and body mass index, respectively. No significant difference in tracking was observed between groups of socioeconomic status. A significant social gradient was observed in both the prevalence of overweight and low physical fitness in the 14-16-year-old adolescents, whereas at the age of 8-10 years, only the prevalence of low physical fitness showed a significant inverse relation to socioeconomic status. The odds of both developing and maintaining risk during the measurement period were estimated as bigger in the group of low socioeconomic status than in the group of high socioeconomic status, although differences were significant only with respect to the odds of developing overweight.

CONCLUSION

The results indicate that the fundamental possibilities of predicting overweight and low physical fitness at an early point in time are the same for different groups of socio-economic status. Furthermore, the observed development of social inequalities in the absolute prevalence of overweight and low physical fitness underline the need for broad preventive efforts targeting children of low socioeconomic status in early childhood.

Life-course experiences and mortality by adult social class among young men

Circumstances over the life-course may contribute to adult social class differences in mortality. However, it is only rarely that the life-course approach has been applied to mortality studies among young adults. The aim of this study is to determine to what extent social class differences in mortality among young Finnish men are explained by living conditions in the parental home and life paths related to transitions in youth. The data for males born in 1956-60 based on the 1990 census records are linked with death records (3184 deaths) by cause of death for 1991-98, and with information on life-course circumstances from the 1970, 1975, 1980, and 1985 censuses. Controlling for living conditions in the parental home-social class, family type, number of siblings, language and region of residence-reduced the high excess mortality of the lower non-manual (RR 1.51, 95% CI: 1.28-1.79), skilled manual (RR 2.94, 2.54-3.40), and unskilled manual class (RR 4.08, 3.51-4.73) by 10% in all-cause mortality. The equivalent reduction for cardiovascular disease was 28% and for alcohol-related causes 16%. The effect of parental home on mortality differences was mainly mediated through its effect on youth paths (pathway model). Educational, marital, and employment paths had a substantial effect-independent of parental home-on social class differences from various causes of death. When all these variables were controlled for adult social class differences in cause specific mortality were reduced by 75-86%. Most of this reduction in mortality differences can be attributed to educational path. However, marital and employment paths had their independent effects, particularly on the excess mortality of unskilled manual workers with disproportionately common exposure to long-term unemployment and living without a partner. In summary, social class differences in total mortality among men in their middle adulthood were only partly determined by parental home but they were mainly attributable to educational, marital, and employment paths in youth.

Associations between blood pressure and overweight defined by new standards for body mass index in childhood

BACKGROUND

Using data from a longitudinal study of young Australians, we applied recent international standards for overweight and obesity to examine associations with blood pressure (BP) and to determine the prevalence and degree of tracking of overweight and obesity. We also aimed to examine socioeconomic status in relation to these variables.

METHODS

BP, height, and weight were measured at 3-year intervals from age 9 to 18, and then at 25 years of age in a Western Australian cohort. At these stages, data were available for 1,036, 1,310, 618, 615 and 600 individuals, respectively.

RESULTS

We found 10% of 9-year-old males to be overweight or obese, while among 12-year-olds, 13% were overweight or obese; at age 15, and still at age 18, overweight or obesity was registered in 17% of this population and it rose to 42% among the 25-year-old young men. The percentage of overweight or obese females at these stages was initially 8, then 12 (at age 12), 11 (at age 15), 14 (at age 18) and finally 32. Overweight or obesity tracked to young adult life in 16% of those overweight or obese at 9, 24% at 12, 34% at 15 and 35% at 18 years. Systolic BP was significantly higher in the overweight or obese except in 12-year-olds. At the age of 25 years, 53% of men had high normal BP or were hypertensive.

CONCLUSIONS

Increasing overweight or obesity in young Australians, consistent with international trends, has serious health implications. Overweight and obesity show tracking and are predictors of higher blood pressure, except in early adolescence.

Genetic and nutritional factors contributing to hyperhomocysteinemia in young adults

A modestly elevated total plasma homocysteine concentration (tHcy) is generally accepted as an independent and graded risk factor for various pathologies, including vascular diseases, neural tube defects, Alzheimer disease, and pregnancy complications. We analyzed 5 common functional polymorphisms in enzymes involved in homocysteine metabolism (ie, methylenetetrahydrofolate reductase [MTHFR] 677C>T and 1298A>C, methionine synthase [MTR] 2756A>G, cystathionine beta-synthase [CBS] 844ins68, and methionine synthase reductase [MTRR] 66A>G) in 452 young adults, and quantified their independent and interactive effects on tHcy concentrations. Serum folate, red cell folate, vitamin B(12), and tHcy concentrations were significantly influenced by MTHFR 677C>T genotypes. A particularly strong interaction was observed between the MTHFR 677TT genotype and serum folate, which led to a high tHcy phenotype that was more pronounced in males. The genetic contribution to the variance in tHcy was estimated to be approximately 9%, compared with approximately 35% that could be attributed to low folate and vitamin B(12). Our study indicates that dietary factors are centrally important in the control of tHcy levels in young adults with additional, but somewhat weaker, genetic effects. These data underscore the potential benefits that may be gained by improving the dietary status of young adults, and provide support for the implementation of folate/B-vitamin food fortification programs.

Genetic and environmental determinants of peak bone mass in young men and women

Peak bone mass is an important risk factor for the development of osteoporosis in later life. Previous work has suggested that genetic, intrauterine, and environmental factors all contribute to the regulation of bone mass, but the ways in which they interact with each other to do so remain poorly understood. In this study, we investigated the relationship between peak bone mass and polymorphisms of the vitamin D receptor (VDR), estrogen receptor (ER) a, and collagen type Ialpha1 (COLIA1) genes in relation to other factors such as birth weight, lifestyle diet, and exercise in a population-based cohort of 216 women and 244 men in their early 20s. Stepwise multiple regression analysis showed that body weight was the strongest predictor of bone mineral density (BMD) in women, accounting for 16.4% of the variance in spine BMD and 8.4% of the variance in femoral neck BMD. Other significant predictors were VDR genotype (3.8%) and carbohydrate intake (1.6%) at the spine and vitamin D intake (3.4%) and ER genotype (3.4%) at the femoral neck. Physical activity was the strongest predictor of BMD in men, accounting for 6.7% of the variance at the spine and 5.1% at the hip. Other significant predictors were body weight (5%) and ER PvuII genotype (2.8%) at the spine and weight (3.4%) and alcohol intake (2%) at the femoral neck. Birth weight was not a significant predictor of BMD at either site but COLIA1 genotype significantly predicted birth weight in women, accounting for 4.3% of the variance. We conclude that peak bone mass is regulated by an overlapping but distinct set of environmental and genetic influences that differ in men and women. However, much of the variance in BMD was unexplained by the variables studied here, which suggests that either most of the genes that regulate BMD remain to be discovered or major environmental influences on BMD exist that have not yet been identified.