Birth weight and blood cholesterol level: a study in adolescents and systematic review

Association Between Birth Weight and Prevalence of Cardiovascular Disease and Other Lifestyle-related Diseases Among the Japanese Population: The JPHC-NEXT Study

BACKGROUND

An association between birth weight and cardiovascular disease (CVD) in adulthood has been observed in many countries; however, only a few studies have been conducted in Asian populations.

METHODS

We used data from the baseline survey (2011-2016) of the Japan Public Health Center-based Prospective Study for the Next Generation Cohort, which included 114,105 participants aged 40-74 years. Adjusted prevalence ratios (aPRs) and 95% confidence intervals (CIs) were calculated from the prevalence of present and past histories of CVD and other lifestyle-related diseases, including hypertension, diabetes, hyperlipidemia, and gout, by birth weight, using Poisson regression.

RESULTS

The prevalence of CVD increased with lower birth weight, with the highest prevalence among those with birth weight under 1,500 grams (males 4.6%; females 1.7%) and the lowest one among those with birth weight at or over 4,000 g (males 3.7%: females 0.8%). Among 88,653 participants (41,156 males and 47,497 females) with complete data on possible confounders, birth weight under 1,500 g was associated with a higher prevalence of CVD (aPR 1.76; 95% CI, 1.37-2.26), hypertension (aPR 1.29; 95% CI, 1.17-1.42), and diabetes (aPR 1.53; 95% CI, 1.26-1.86) when a birth weight of 3,000-3,999 grams was used as the reference. Weaker associations were observed for birth weight of 1,500-2,499 grams and 2,500-2,999 grams, while no significant associations were observed for birth weight at or over 4,000 grams. The association between birth weight and the prevalence of hyperlipidemia was less profound, and no significant association was observed between birth weight and gout.

CONCLUSION

Lower birth weight was associated with a higher prevalence of CVD, hypertension, and diabetes in the Japanese population.

Effects of size at birth on health, growth and developmental outcomes in children up to age 18: an umbrella review

BACKGROUND

Size at birth, an indicator of intrauterine growth, has been studied extensively in relation to subsequent health, growth and developmental outcomes. Our umbrella review synthesises evidence from systematic reviews and meta-analyses on the effects of size at birth on subsequent health, growth and development in children and adolescents up to age 18, and identifies gaps.

METHODS

We searched five databases from inception to mid-July 2021 to identify eligible systematic reviews and meta-analyses. For each meta-analysis, we extracted data on the exposures and outcomes measured and the strength of the association.

FINDINGS

We screened 16 641 articles and identified 302 systematic reviews. The literature operationalised size at birth (birth weight and/or gestation) in 12 ways. There were 1041 meta-analyses of associations between size at birth and 67 outcomes. Thirteen outcomes had no meta-analysis.Small size at birth was examined for 50 outcomes and was associated with over half of these (32 of 50); continuous/post-term/large size at birth was examined for 35 outcomes and was consistently associated with 11 of the 35 outcomes. Seventy-three meta-analyses (in 11 reviews) compared risks by size for gestational age (GA), stratified by preterm and term. Prematurity mechanisms were the key aetiologies linked to mortality and cognitive development, while intrauterine growth restriction (IUGR), manifesting as small for GA, was primarily linked to underweight and stunting.

INTERPRETATION

Future reviews should use methodologically sound comparators to further understand aetiological mechanisms linking IUGR and prematurity to subsequent outcomes. Future research should focus on understudied exposures (large size at birth and size at birth stratified by gestation), gaps in outcomes (specifically those without reviews or meta-analysis and stratified by age group of children) and neglected populations.

PROSPERO REGISTRATION NUMBER

CRD42021268843.

Extreme Birth Weight and Metabolic Syndrome in Children

Small and large birth weights (BWs) for gestational age (GA) represent extremes, but the correlation between extreme BW and metabolic syndrome (MetS) has not been fully elucidated. In this study, we examined this correlation in obese children based on changes in their metabolic profile from childhood to adolescence. A retrospective observational study was performed on 535 obese patients aged 0–18 years in the Clinical and Emergency Hospital for Children “Louis Turcanu” in Timisoara, Romania, based on clinical and biological data from January 2015 to December 2019. We emphasized the links between extreme BW and obesity, extreme BW and cardiometabolic risk, obesity and cardiometabolic risk, and extreme BW, obesity and MetS. Children born large for gestational age (LGA) predominated over those born small for gestational age (SGA). Our findings showed that BW has an independent effect on triglycerides and insulin resistance, whereas obesity had a direct influence on hypertension, impaired glucose metabolism and hypertriglyceridemia. The influences of BW and obesity on the development of MetS and its components are difficult to separate; therefore, large prospective studies in normal-weight patients are needed.

Birthweight and Lipids in Adult Life: Population-Based Cross Sectional Study

The purpose of this study was to examine the association of birthweight with lipid profile in the general adult population. Participants in the second-wave of a nationally representative cross sectional AusDiab-study were asked to complete a birthweight questionnaire. Fasting total cholesterol (TC), LDL-C, HDL-C, and triacylglycerol levels were modeled against birthweight. Four thousand five hundred and two people reported their birthweights, mean (SD) of 3.4(0.7) kg. Females with low birthweight-LBW had higher levels of TC, LDL-C, and triacylglycerols, but no difference in HDL-C, than those with normal-birthweight-NBW;≥2.5 kg. People with LBW showed a trend toward increased risk for high TC (≥5.5 mmol/L) compared to NBW. Among females with LBW, the risk for high LDL-C (≥3.5 mmol/L) was increased compared to those of NBW. The risk for low HDL-C (<0.9 mmol/L) was increased among males with LBW compared to those with NBW. Examination of the relationship on the continuum showed no differences except for high triacylglycerol levels among females with the lowest birthweight quintile compared to the higher birthweight quintile. However, the risk for various abnormalities by birthweight quintiles was similar to that when we used the traditional definition of LBW vs. NBW. Females and males with low birthweight differ in their risk for lipids abnormalities. Females had higher risk for high LDL-C, whereas males had high risk for low HDL-C (<0.9 mmol/L). In addition, females with low birthweight had the highest triacylglycerol levels. High LDL-C, low HDL-C, and high triacylglycerols are well-recognized risk factors for cardiovascular disease.

Chemerin concentrations in infants born small for gestational age: correlations with triglycerides and parameters related to glucose homeostasis

Infants born small for gestational age (SGA) are known to have increased risk of developing several pathologies, including the metabolic syndrome, when they grow up. It has been described that both the growth pattern of these children as well as the risk of their presenting future metabolic disorders can be influenced by the expression of adipokines. Among them, chemerin has demonstrated to be implicated in lipid and glucose metabolism, presenting higher circulating concentration in diabetic and obese subjects. Thus, the aim of this study was to analyze the association of anthropometric parameters and plasmatic biochemical parameters with circulating chemerin concentration in SGA children. This prospective, longitudinal study was carried out in plasma samples of Caucasian children born SGA at Hospital Universitario de Álava-Txagorritxu. Significant positive correlations were observed between chemerin concentrations at 3 months and insulin values at 3 months and also with triglyceride levels at 24 months. These associations were maintained after adjustment by anthropometric parameters. Therefore, we suggest that circulating chemerin concentration, measured at an early age, might be an indicator of future metabolic alterations in SGA children.

Association between birth weight and childhood cardiovascular disease risk factors in West Virginia

The reported associations between birth weight and childhood cardiovascular disease (CVD) risk factors have been inconsistent. In this study, we investigated the relationship between birth weight and CVD risk factors at 11 years of age. This study used longitudinally linked data from three cross-sectional datasets (N = 22,136) in West Virginia; analysis was restricted to children born full-term (N = 19,583). The outcome variables included resting blood pressure [systolic blood pressure (SBP), diastolic blood pressure (DBP)] and lipid profile [total cholesterol (TC), low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, non-HDL, and triglycerides (TG)]. Multiple regression analyses were performed, adjusting for child's body mass index (BMI), sociodemographics, and lifestyle characteristics. Unadjusted analyses showed a statistically significant association between birth weight and SBP, DBP, HDL, and TG. When adjusted for the child's BMI, the association between birth weight and HDL [b = 0.14 (95% CI: 0.11, 0.18) mg/dl per 1000 g increase] and between birth weight and TG [b = -0.007 (-0.008, -0.005) mg/dl per 1000 g increase] remained statistically significant. In the fully adjusted model, low birth weight was associated with higher LDL, non-HDL, and TGs, and lower HDL levels. The child's current BMI at 11 years of age partially (for HDL, non-HDL, and TG) and fully mediated (for SBP and DBP) the relationship between birth weight and select CVD risk factors. While effects were modest, these risk factors may persist and amplify with age, leading to potentially unfavorable consequences in later adulthood.

Small for gestational age and obesity related comorbidities

Infant born small for gestational age (SGA) are at increased risk of perinatal morbidity, persistent short stature and metabolic alterations in later life. The result of SGA followed by rapid weight gain during early postnatal life has been associated with increased long-term risks for central obesity, insulin resistance, impaired glucose tolerance, type 2 diabetes, hypertension, increased fat mass, and cardiovascular disease. We should carefully monitor their weight during infancy and childhood to prevent excessive rates of weight gain. 'Healthy catch up growth' may decreased the risk of obesity-related comorbidities in SGA. Establishing the optimal growth patterns in SGA to minimize short- and long-term risks is important, and further studies will be needed. This review discusses recent studies concentrating on obesity-related morbidities in SGA infants that may provide insight into growth monitoring.

Metabolic signatures of birthweight in 18 288 adolescents and adults

BACKGROUND

Lower birthweight is associated with increased susceptibility to cardiometabolic diseases in adulthood, but the underlying molecular pathways are incompletely understood. We examined associations of birthweight with a comprehensive metabolic profile measured in adolescents and adults.

METHODS

High-throughput nuclear magnetic resonance metabolomics and biochemical assays were used to quantify 87 circulating metabolic measures in seven cohorts from Finland and the UK, comprising altogether 18 288 individuals (mean age 26 years, range 15-75). Metabolic associations with birthweight were assessed by linear regression models adjusted for sex, gestational age and age at blood sampling. The metabolic associations with birthweight were compared with the corresponding associations with adult body mass index (BMI).

RESULTS

Lower birthweight adjusted for gestational age was adversely associated with cardiometabolic biomarkers, including lipoprotein subclasses, fatty acids, amino acids and markers of inflammation and impaired liver function (P < 0.0015 for 46 measures). Associations were consistent across cohorts with different ages at metabolic profiling, but the magnitudes were weak. The pattern of metabolic deviations associated with lower birthweight resembled the metabolic signature of higher adult BMI (R² = 0.77) assessed at the same time as the metabolic profiling. The resemblance indicated that 1 kg lower birthweight is associated with similar metabolic aberrations as caused by 0.92 units higher BMI in adulthood.

CONCLUSIONS

Lower birthweight adjusted for gestational age is associated with adverse biomarker aberrations across multiple metabolic pathways. Coherent metabolic signatures between lower birthweight and higher adult adiposity suggest that shared molecular pathways may potentially underpin the metabolic deviations. However, the magnitudes of metabolic associations with birthweight are modest in comparison to the effects of adiposity, implying that birthweight is only a weak indicator of the metabolic risk profile in adulthood.

Birth Weight, Postnatal Weight Gain, and Childhood Adiposity in Relation to Lipid Profile and Blood Pressure During Early Adolescence

Background

Different pathways likely underlie the association between early weight gain and cardiovascular disease risk. We examined whether birth weight for length relationship and weight gain up to 2 years of age are associated with lipid profiles and blood pressure (BP) in early adolescence and determined whether childhood adiposity mediates these associations.

Methods and Results

Data from QUALITY (Quebec Adipose and Lifestyle Investigation in Youth), a cohort of white children with parental history of obesity, were analyzed (n=395). Sex‐specific weight for length z scores from birth to 2 years were computed. Rate of postnatal weight gain was estimated using individual slopes of weight for length z‐score measurements. Percentage of body fat was measured at 8 to 10 years. Fasting lipids and BP were measured at 10 to 12 years. Using path analysis, we found indirect effects of postnatal weight gain, through childhood adiposity, on all outcomes: Rate of postnatal weight for length gain was positively associated with childhood adiposity, which in turn was associated with unfavorable lipid and BP levels in early adolescence. In contrast, small beneficial direct effects on diastolic BP z scores, independent of weight at other time points, were found for birth weight for length (β=−0.05, 95% CI, −0.09 to −0.002) and for postnatal weight gain (β=−0.02, 95% CI, −0.03 to −0.002).

Conclusions

Among children with at least 1 obese parent, faster postnatal weight gain leads to cardiovascular risk factors in early adolescence through its effect on childhood adiposity. Although heavier newborns may have lower BP in early adolescence, this protective direct effect could be offset by a deleterious indirect effect linking birth weight to later adiposity.

The reasons why cardiologists should consider prematurity at birth and intrauterine growth retardation among risk factors

The survival percentage of infants born preterm has risen steadily worldwide thanks to the giant steps forward made in the field of perinatal (the period immediately after birth) and neonatal (the first 4 weeks of birth following delivery) medicine. However, prematurity at birth and consequent low birth weight still represent the major causes of neonatal morbidity and mortality. Infants born preterm are at high risk of developing neurological, ophthalmological, and gastrointestinal complications as well. Furthermore, extensive more recent epidemiological findings have demonstrated an increase in risk factors and a higher mortality rate due to cardiovascular causes in patients born preterm and/or with intrauterine growth restriction. The aim of this review is to provide scientific evidence about how the cardiovascular system may be negatively influenced by prematurity and by a low birth weight that should by rights be viewed as new cardiovascular risk factors. This condition is referred to as 'cardiovascular perinatal programming'. In the light of the above, an early, constant, and prolonged cardiovascular follow-up should be implemented in former preterm individuals.

Birth weight and risk of ischemic heart disease: A Mendelian randomization study

Low birth weight is a risk factor for cardiovascular disease. However, the association could be confounded by many factors. We used Mendelian randomization to clarify the role of birth weight in ischemic heart disease (IHD) and lipids. We used all 7 single nucleotide polymorphisms (SNPs) independently contributing to birth weight at genome wide significance (p < 5 × 10⁻⁸) in separate sample instrumental variable analysis to estimate the effect of birth weight on IHD using the CARDIoGRAMplusC4D 1000 Genomes based GWAS case (n = 60,801)-control (n = 123,504) study and on lipids using GLGC (n = 188,577). Higher genetically predicted birth weight was associated with lower risk of IHD (odds ratio (OR) 0.96 per 100 grams, 95% confidence interval (CI) 0.93 to 0.99), but the association was not robust to sensitivity analyses excluding SNPs related to height or use of weighted median methods. Genetically predicted birth weight was not associated with low density lipoprotein cholesterol or triglycerides, but was associated with lower high density lipoprotein cholesterol (−0.014 standard deviation, 95% CI −0.027 to −0.0005) and the association was more robust to the sensitivity analyses. Our study does not show strong evidence for an effect of birth weight on IHD and lipids.

Birth weight in relation to health and disease in later life: an umbrella review of systematic reviews and meta-analyses

BACKGROUND

Birth weight, a marker of the intrauterine environment, has been extensively studied in epidemiological research in relation to subsequent health and disease. Although numerous meta-analyses have been published examining the association between birth weight and subsequent health-related outcomes, the epidemiological credibility of these associations has not been thoroughly assessed. The objective of this study is to map the diverse health outcomes associated with birth weight and evaluate the credibility and presence of biases in the reported associations.

METHODS

An umbrella review was performed to identify systematic reviews and meta-analyses of observational studies investigating the association between birth weight and subsequent health outcomes and traits. For each association, we estimated the summary effect size by random-effects and fixed-effects models, the 95 % confidence interval, and the 95 % prediction interval. We also assessed the between-study heterogeneity, evidence for small-study effects and excess significance bias. We further applied standardized methodological criteria to evaluate the epidemiological credibility of the statistically significant associations.

RESULTS

Thirty-nine articles including 78 associations between birth weight and diverse outcomes met the eligibility criteria. A wide range of health outcomes has been studied, ranging from anthropometry and metabolic diseases, cardiovascular diseases and cardiovascular risk factors, various cancers, respiratory diseases and allergies, musculoskeletal traits and perinatal outcomes. Forty-seven of 78 associations presented a nominally significant summary effect and 21 associations remained statistically significant at P < 1 × 10^-6. Thirty associations presented large or very large between-study heterogeneity. Evidence for small-study effects and excess significance bias was present in 13 and 16 associations, respectively. One association with low birth weight (increased risk for all-cause mortality), two dose-response associations with birth weight (higher bone mineral concentration in hip and lower risk for mortality from cardiovascular diseases per 1 kg increase in birth weight) and one association with small-for-gestational age infants with normal birth weight (increased risk for childhood stunting) presented convincing evidence. Eleven additional associations had highly suggestive evidence.

CONCLUSIONS

The range of outcomes convincingly associated with birth weight might be narrower than originally described under the "fetal origin hypothesis" of disease. There is weak evidence that birth weight constitutes an effective public health intervention marker.

Birth weight was longitudinally associated with cardiometabolic risk markers in mid-adulthood

PURPOSE

Birth weight (BW) is associated with risk of cardiovascular (CV) disease. The findings from studies examined the association of BW with metabolic markers of CV risk were inconsistent and controversial. We examined the association of BW with insulin resistance and blood lipids using repeated measures up to mid-adulthood.

METHODS

Data from seven screenings of the Bogalusa Heart Study-a longitudinal study of cardiovascular risk factors in Bogalusa, LA-are analyzed using generalized estimation equations method. Participants with birth data and at least one measurement of study outcomes between 18 and 44 years (n = 2,034) were included.

RESULTS

BW is inversely associated with insulin resistance, triglycerides, and total cholesterol (P < .01 for all). For 1-kg decrease in BW, insulin resistance increased by 2.3 units, 95% confidence interval (CI) = 0.7-3.9; triglycerides by 8.7 mg per dL, 95% CI = 4.9-12.4, and total cholesterol by 5.4 mg per dL, 95% CI = 1.8-9.1. The association of body mass with adult blood lipids levels is weaker in persons with low versus normal BW.

CONCLUSIONS

The study provides strong evidence of an inverse relationship of BW with adulthood cardiometabolic risk profile. Persons born with low BW are maybe less responsive to preventive interventions aiming at weight reduction.

Effect of preterm birth on growth and cardiovascular disease risk at school age

BACKGROUND

Low birthweight is associated with increased risk for cardiovascular disease (CVD) in later life, but whether premature birth is also a risk factor for CVD has not been fully determined. The aim of this study was to investigate the relationship between gestational age and risk factors for CVD at school age.

METHODS

Using medical check-up data of school children, the relationship between gestational age and height, weight, body mass index, blood pressure, and lipid profiles at ages 9 and 12 years were investigated in children born preterm and admitted to neonatal intensive care unit at birth (n = 182; 115 boys and 67 girls). These data were also compared between preterm small for gestational age (SGA) children and preterm appropriate for gestational age (AGA) children.

RESULTS

Gestational age was positively associated with height, and inversely associated with systolic blood pressure at school age. Preterm SGA children were significantly shorter and lighter at 9 and 12 years of age compared with preterm AGA children, but there were no significant differences in any CVD risk factors between the groups.

CONCLUSIONS

In preterm infants, a shorter duration of gestation is associated with higher systolic blood pressure at school age.

Birth weight and risk factors for cardiovascular disease and type 2 diabetes in US children and adolescents: 10 year results from NHANES

Previous studies have shown that birth weight and other birth characteristics may be associated with risk for type 2 diabetes and cardiovascular disease (CVD) later in life; however, results using large US national survey data are limited. Our goal was to determine the aforementioned associations using nationally representative data. We studied children and adolescents 6-15 years using data from the National Health and Nutrition Examination Survey cycles 2001-2010. Survey and examination data included demographic and early childhood characteristics, current health status, physical activity information, anthropometric measurements, dietary data (total energy, saturated fat, sodium, and sugar intakes), biomarkers related to selected risk factors of CVD [systolic blood pressure (SBP), plasma C-reactive protein (CRP) and lipid profiles], and type 2 diabetes [fasting glucose, insulin, and homeostasis model assessment (HOMA)]. Birth weight (proxy-reported) was inversely associated with SBP among girls; SBP levels increased 1.4 mmHg for each 1,000 g decrease in birth weight (p = 0.003) after controlling for potential confounders. Birth weight was not associated with levels of CRP or lipid profiles across the three racial groups. In addition, birth weight was inversely related to levels of fasting insulin and HOMA among non-Hispanic Whites; for each 1,000 g decrease in birth weight, fasting insulin levels increased 9.1% (p = 0.007) and HOMA scores increased 9.8% (p = 0.007). Birth weight was inversely associated with the levels of SBP, fasting insulin, and HOMA. These results support a role for birth weight, independent of the strong effects of current body weight status, in increasing risk for CVD and type 2 diabetes.

When is birthweight at term (≥37 weeks' gestation) abnormally low? A systematic review and meta-analysis of the prognostic and predictive ability of current birthweight standards for childhood and adult outcomes

BACKGROUND

Health outcomes throughout the life course have been linked to fetal growth restriction and low birthweight. A variety of measures exist to define low birthweight, with a lack of consensus regarding which predict adverse outcome.

OBJECTIVES

To evaluate the relationship between birthweight standards and childhood and adult outcomes in term-born infants (≥37 weeks' gestation).

SEARCH STRATEGY

MEDLINE (1966-January 2011), EMBASE (1980-January 2011), and the Cochrane Library (2011:1) and MEDION were included.

SELECTION CRITERIA

Studies comprising live term-born infants (gestation ≥37 completed weeks), with weight or other anthropometric measurements recorded at birth along with childhood and adult outcomes.

DATA COLLECTION AND ANALYSIS

Data were extracted to populate 2 × 2 tables relating birthweight standard with outcome, and meta-analysis was performed where possible.

MAIN RESULTS

Fifty-nine articles (2 600 383 individuals) were selected. There was no significant relationship between birthweight <2.5 kg (odds ratio [OR] 0.98, 95% confidence intervals [CI] 0.87-1.10) and composite measure of childhood morbidity. Weight <10th centile on the population nomogram showed a small association (OR 1.49, 95% CI 1.02-2.19) for the same outcome. There was no significant association between either of the above measures and adult morbidity. The relationship between other measures and individual outcomes varied.

AUTHOR'S CONCLUSIONS

The association between low birthweight, by any definition, and childhood and adult morbidity was inconsistent. None of the current standards of low birthweight was a good predictor of adverse outcome.

Relationships between birth weight and serum cholesterol levels in healthy Japanese late adolescents

Poor growth in utero has been suggested to be associated with adverse levels of serum cholesterol concentrations in later life. In Asia, there have only been a limited number of studies examining the relationship between fetal status and serum lipids, especially in adolescents. The objective of this study was to examine the relationships between birth weight and serum high-density lipoprotein (HDL) and low-density lipoprotein (LDL) cholesterol levels; adjusting for current physical status including percent body fat, physical activity and nutrient intake in healthy Japanese late adolescents. The data of 573 late adolescents with an average age of 17.6 (287 boys and 286 girls) who underwent physical examinations which included blood sampling and who had all the required data, were analyzed. Birth weight was obtained from their maternal and child health handbook. Multiple regression analysis showed that birth weight was positively associated with serum HDL in girls, independently of percent body fat or fat intake, when adjusted for current body height and weight. There were no associations between birth weight and serum HDL in boys, or serum LDL in either sex.

Lipid profile and atherogenic indices soon after birth in Japanese preterm infants

AIM

The intra-uterine environment affects the risk of development of cardiovascular disease in adulthood. The aim of this study was to determine the influence of prematurity and foetal growth restriction on lipid metabolism, by assessing atherogenic indices soon after birth in preterm infants.

METHODS

Blood samples were collected within 20 min of birth from 80 preterm infants with a gestational age of ≤35 weeks. Serum total cholesterol (TC), low-density lipoprotein cholesterol (LDLc), high-density lipoprotein cholesterol (HDLc), apolipoprotein-A1 (apoA1) and apolipoprotein-B (apoB) levels were measured. The ratio of TC/HDLc, LDLc/HDLc and apoB/apoA1 were also calculated. Correlations between these indices and gestational age, birth weight and the standard deviation (SD) score for birth weight were also determined.

RESULTS

Gestational age, birth weight and SD score for birth weight were negatively correlated with the TC/HDLc, LDLc/HDLc and apoB/apoA1 ratios.

CONCLUSION

In preterm infants, prematurity and poor foetal growth may influence lipid and apolipoprotein metabolism and affect atherogenic indices at birth.

Adult lipids associated with early life growth in traditional Melanesian societies undergoing rapid modernization: a longitudinal study of the mid-20th century

Both poor fetal development and accelerated post-natal growth have been linked to adult dyslipidemias in many studies conducted in developed societies. It is not known, however, whether these relationships only characterize populations with typical Western diets or if they also may develop in groups at the early stages of a dietary transition. Our longitudinal study of traditional rural populations in the Southwest Pacific during a period of extremely rapid modernization in diet and life-styles shows a nascent association between child growth retardation, subsequent growth acceleration, and adult lipid values in spite of a continuing prevalence of very low lipid levels. However, our results do not entirely conform to results from populations with "modern" diets. Outcome (i.e., young adult) cholesterol and triglyceride levels are more consistently related to initial measures of body fat and growth in body fat measures than with stature, while outcome apo A-1 is more consistently related to initial stature or stature growth than to measures of body fat. We suggest this may reflect a pattern characteristic of the initial stages of "modernization" associated with dietary change, with stronger and more pervasive relationships emerging only later as populations complete the dietary transition.

Pregnancy Complications and the Risk of Metabolic Syndrome for the Offspring

Metabolic syndrome is a growing problem globally, and is a contributor to non-communicable diseases such as type II diabetes and cardiovascular disease. The risk of developing specific components of the metabolic syndrome such as obesity, hyperlipidemia, hypertension, and elevated fasting blood sugar has been largely attributed to environmental stressors including poor nutrition, lack of exercise, and smoking. However, large epidemiologic cohorts and experimental animal models support the "developmental origins of adult disease" hypothesis, which posits that a significant portion of the risk for adult metabolic conditions is determined by exposures occurring in the perinatal period. Maternal obesity and the rate of complications during pregnancy such as preterm birth, preeclampsia, and gestational diabetes continue to rise. As our ability to reduce perinatal morbidity and mortality improves the long-term metabolic consequences remain uncertain, pointing to the need for further research in this area.

Life course body mass index, birthweight and lipid levels in mid-adulthood: a nationwide birth cohort study

AIMS

Improvement in lipid profiles is an important public health and clinical goal for which a better understanding is needed of biological pathways and influences. Evidence is scant on the role of growth, including trajectories of body mass index (BMI), so we aimed to determine whether particular life stages from birth to adulthood are important for lipid levels in mid-adulthood (45 years).

METHODS AND RESULTS

In the 1958 British birth cohort (n = 3927 men; 3897 women), weight and height were recorded at: birth (weight only), 7, 11, 16, 23, 33, and 45 years. Birthweight was inversely associated with triglycerides and in women with total- and non-high-density lipoprotein cholesterol; associations were little affected by adjustment for 7-year BMI. Associations between lipids and BMI strengthened with age, e.g. in women, adult (45-year) triglycerides were elevated by 1.54% (95% confidence interval: 0.87-2.21%) and 3.57% (3.29-3.86%), respectively, per kg/m² higher BMI at 11 and 45 years. Body mass index gain was related to lipids, with strongest associations for the interval between 33 and 45 years, where a kg/m² gain in BMI was associated with ~0.6% higher total cholesterol and ~5.3% higher triglycerides. Associations between 45-year BMI and lipids were stronger for those with lowest than highest BMI at younger ages (P for interaction ≤0.05). A long duration of obesity and obesity in childhood but not thereafter were unrelated to adult lipid levels.

CONCLUSIONS

Our findings from a large population-based cohort highlight detrimental consequences of high adult BMI for lipids as most pronounced for those with a lower BMI at earlier life stages.

Association between low birth weight and high adult waist-to-height ratio in non-obese women: a cross-sectional study in a Japanese population

Low birth weight has been associated with cardiovascular diseases. The waist-to-height ratio is a good indicator of risks for these diseases. The objective of this study was to examine the associations between birth weight and adult waist-to-height ratio in a Japanese population. A cross-sectional study, comprised of 851 subjects (401 men and 450 women) aged 35-62 years who were born at full term, was conducted at a medical checkup. The subjects responded to a questionnaire about weight at birth, and data on physical characteristics were collected from the results of the medical checkup. The subjects were stratified with sex and a Body Mass Index of 25 kg/m(2) to elucidate the effects of birth weight on adult waist-to-height ratio. Analysis of covariance was used to compare the physical condition among the 4 birth weight categories. After adjusting for age, alcohol consumption, smoking status and exercise, the height was significantly lower in the birth weight < 2,500 g category among men (P < 0.001) and women (P < 0.001), while the waist-to-height ratio was significantly higher in the birth weight < 2,500 g category, compared with the > 3,500 g category in the non-obese women (P = 0.004), but not in the obese women. In conclusion, low birth weight was independently associated with a low adult height among men and women and with a high adult waist-to-height ratio among non-obese women. Our results suggest that intrauterine environmental insults might lead to accumulation of visceral fat among non-obese women.

The fetal origins of adult disease: a narrative review of the epidemiological literature

The fetal origins of adult disease (FOAD) hypothesis suggests that risk factors from intrauterine environmental exposures affect the fetus' development during sensitive periods, and increases the risk of specific diseases in adult life. This link was initially observed between prenatal exposures and adult coronary heart disease, but corresponding observations have later been published for a range of chronic conditions. Although the hypothesis has been praised as an essential shift in our understanding of determinants for health, the hypothesis has also been criticized on a number of accounts, both methodologically and theoretically. The aim of this paper is to critically discuss the FOAD-hypothesis, in relation to the epidemiological evidence. We conclude that much of the research literature on the FOAD-hypothesis finds support for the hypothesis. Despite this, it is still unclear if the effects are independent and what the public health relevance is. Notwithstanding the heart of the hypothesis – that environmental influences during gestation have an effect on later development – should be considered a major insight and constitutes a complement to a focus on genetic and more proximal factors (such as adult lifestyle) as causes of adult disease. As the search for determinants for disease and health continues, the FOAD-hypothesis is likely to remain an important perspective. It may however be better positioned as part of a broader life course perspective, rather than as an independent hypothesis.

Prematurity and low weight at birth as new conditions predisposing to an increased cardiovascular risk

Although the survival rate for preterm subjects has improved considerably, due to the progress in the field of perinatal medicine, preterm birth is frequently the cause underlying a series of notorious complications: morphological, neurological, ophthalmological, and renal alterations. In addition, it has recently been demonstrated how low gestational age and reduced foetal growth contribute towards an increased cardiovascular risk in preterm neonates. In fact, cardiovascular mortality is higher among former preterm adults than those born at term. This condition is referred to as cardiovascular perinatal programming. In the light of the above, an early, constant, and prolonged cardiological followup programme should be implemented in former preterm individuals. The aim of this paper was to perform a comprehensive literature review about two new emerging conditions predisposing to an increased cardiovascular risk: prematurity and low weight at birth.

Early-life determinants of total and HDL cholesterol concentrations in 8-year-old children; the PIAMA birth cohort study

BACKGROUND

Adult cholesterol concentrations might be influenced by early-life factors, such as breastfeeding and birth weight, referred to as "early programming". How such early factors exert their influence over the life course is still poorly understood. Evidence from studies in children and adolescents is scarce and conflicting. We investigated the influence of 6 different perinatal risk factors on childhood total and HDL cholesterol concentrations and total-to-HDL cholesterol ratio measured at 8 years of age, and additionally we studied the role of the child's current Body Mass Index (BMI).

METHODS

Anthropometric measures and blood plasma samples were collected during a medical examination in 751 8-year-old children participating in the prospective Prevention and Incidence of Asthma and Mite Allergy (PIAMA) birth cohort study. Linear and logistic regression were performed to estimate associations of total and HDL cholesterol concentrations with breastfeeding, birth weight, infant weight gain, maternal overweight before pregnancy, gestational diabetes and maternal smoking during pregnancy, taking into account the child's current BMI.

RESULTS

Linear regressions showed an association between total-to-HDL cholesterol ratio and maternal pre-pregnancy overweight (β = 0.15, Confidence Interval 95% (CI): 0.02, 0.28), rapid infant weight gain (β = 0.13, 95%CI: 0.01, 0.26), and maternal smoking during pregnancy (β = 0.14, 95%CI: 0.00, 0.29). These associations were partly mediated by the child's BMI.

CONCLUSION

Total-to-HDL cholesterol ratio in 8-year-old children was positively associated with maternal pre-pregnancy overweight, maternal smoking during pregnancy and rapid infant weight gain.

Combined analysis of CHRNA5, CHRNA3 and CYP2A6 in relation to adolescent smoking behaviour

CYP2A6 influences smoking uptake in adolescence. Genetic variation in the CHRNA5-CHRNA3 region influences smoking behaviour in adults. However, their combined effects on smoking in adolescence have not been tested to date. We present data on 1450 adolescents from the Ten Towns Heart Health Study (TTHHS) extensively phenotyped for smoking-related traits during adolescence. Single nucleotide polymorphisms from CHRNA5 and CHRNA3 (previously associated with smoking), were typed in our study population, previously genotyped for CYP2A6. Association analyses between each genotype and both smoking status and behavioural markers of smoking were performed. rs16969968 in CHRNA5 was associated both at 13-15 years and 18 years with current smoking amongst adolescents who had tried smoking (OR = 1.82, CI = 1.10-3.01, p = 0.02 at age 13-15; OR = 2.39, CI = 1.37-4.17, p = 0.002 at age 18). No association was found for rs578776 in CHRNA3. The effects of CHRNA5 and CYP2A6 genotypes in TTHHS appeared to be independent, with each approximately doubling the odds of being a regular smoker by age 18 years. CYP2A6 genotype insufficiency increases adolescent likelihood of being a regular smoker but increases later life quitting likelihood and reduces average consumption. In contrast, CHRNA5 genotype, acting recessively, affects smoking similarly in adolescents and older adults. These contrasting actions, in digenic combination, illustrate behavioural genetic complexity.

Relationship between birth size and coronary heart disease in China

BACKGROUND

Clinical epidemiological studies suggested a link between fetal growth conditions and later coronary heart disease (CHD) in adult life. However, no such studies have been conducted in a Chinese population.

OBJECTIVES

We investigated the association between various birth characteristics and CHD occurrence in a Chinese cohort.

DESIGN

Retrospective cohort study.

SETTING

Peking Union Medical College Hospital, Beijing, China.

PARTICIPANTS

A total of 2,033 subjects who were born at Peking Union Medical College Hospital between 1921 and 1954.

MEASUREMENTS

Neonatal birth-weight, placental weight, length from crown to heel, head circumference, and biparietal and occipitofrontal diameters were routinely recorded at the time of birth. All participants were followed up between May 2002 and April 2004 for the occurrence of CHD.

RESULTS

CHD was identified in 135 patients. The occurrence of CHD was inversely related to birth sizes, such as birth-weight, head circumference, placental weight (P < 0.05), but was not significantly related to birth length or ponderal index (birth-weight/birth length(3)). After multivariable logistic regression, the ratio of birth-weight to birth length was an independent predictor of CHD along with two other variables: obesity and age.

LIMITATIONS

This was a single-center retrospective study.

CONCLUSIONS

In China low birth size or birth disproportion, which is suggestive of fetal growth retardation, has an effect on CHD occurrence during adulthood. This suggests that environmental factors operate in both the prenatal and postnatal periods with regard to the development of CHD.

Birth weight and blood lipid levels in Spanish adolescents: influence of selected APOE, APOC3 and PPARgamma2 gene polymorphisms. The AVENA Study

Background

There is increasing evidence indicating that genes involved in certain metabolic processes of cardiovascular diseases may be of particular influence in people with low body weight at birth. We examined whether the apolipoprotein (APO) E, APOC3 and the peroxisome proliferator-activated receptor-γ-2 (PPARγ2) polymorphisms influence the association between low birth weight and blood lipid levels in healthy adolescents aged 13–18.5 years.

Methods

A cross-sectional study of 502 Spanish adolescents born at term was conducted. Total (TC) and high density lipoprotein cholesterol (HDLc), triglycerides (TG), apolipoprotein (apo) A and B, and lipoprotein(a) [Lp(a)] were measured. Low density lipoprotein cholesterol (LDLc), TC-HDLc, TC/HDLc and apoB/apoA were calculated.

Results

Low birth weight was associated with higher levels of TC, LDLc, apoB, Lp(a), TC-HDLc, TC/HDLc and apoB/apoA in males with the APOE ε3ε4 genotype, whereas in females, it was associated with lower HDLc and higher TG levels. In males with the APOC3 S1/S2 genotype, low birth weight was associated with lower apoA and higher Lp(a), yet this association was not observed in females. There were no associations between low birth weight and blood lipids in any of the PPARγ2 genotypes.

Conclusion

The results indicate that low birth weight has a deleterious influence on lipid profile particularly in adolescents with the APOE ε3/ε4 genotype. These findings suggest that intrauterine environment interact with the genetic background affecting the lipid profile in later life.

Association between low birth weight and elevated white blood cell count in adulthood within a Japanese population

BACKGROUND

Epidemiological studies have demonstrated the association between low birth weight and increased adulthood risk for cardiovascular and metabolic diseases. However, the precise mechanism underlying the association remains poorly understood. We investigated the association between birth weight and adult white blood cell (WBC) count in a Japanese population.

METHODS AND RESULTS

The subjects were 779 men and 209 women aged 35-64 years. The mean WBC count was 5,283 /microl (SD: 1,326). Birth weight was divided to 6 categories: <2,500, 2,500-<2,800, 2,800-<3,000, 3,000-<3,200, 3,200-<3,500, and >3,500 g. Estimated WBC counts were 5,729, 5,341, 5,301, 5,212, 5,013 and 5,372 for the subjects with birth weights of the above respective categories (p=0.015, trend p=0.016) by one-way analysis of covariance after adjustments for sex, age, height, body mass index (BMI), lifestyles, and chronic diseases. This association was pronounced among the subjects with a BMI <25.0 kg/m2 rather than those with a higher BMI.

CONCLUSIONS

These findings support the idea that part of the association of low birth weight with elevated risk for vascular and metabolic diseases in later life could be mediated by an inflammatory pathway.

Low-density lipoprotein profile changes during the neonatal period

OBJECTIVE

To investigate natural change of low-density lipoprotein (LDL) profile during the neonatal period and the impact of gestational age and birth weight on those changes.

STUDY DESIGN

We measured lipid composition in LDL fraction, LDL particle size and apolipoprotein B (apoB) concentration at birth, 5 days of age and 1 month of age in 63 healthy neonates that had 37 to 41-week gestational age.

RESULT

Low-density lipoprotein cholesterol and apoB concentrations increased from birth to 5 days of age, and the concentration persisted at 1 month in breast-fed and mixed-fed infants. However, in formula-fed infants, the concentration decreased at 1 month. At 5 days of age, neonates had larger and more triglyceride (TG)-rich LDL particles than at birth. At 1 month of age, LDL particles were smaller and more cholesterol rich than at 5 days of age. Single regression analyses showed that gestational age had influenced the LDL profile at birth and 5 days of age, while at 1 month milk determined the profile.

CONCLUSION

The number of LDL particles increased rapidly during the first 5 days of life, and the composition of LDL particles is modulated by TG content throughout the neonatal period. Gestational age and milk, rather than birth weight, determine postnatal changes in LDL profile.

Maternal and child undernutrition: consequences for adult health and human capital

In this paper we review the associations between maternal and child undernutrition with human capital and risk of adult diseases in low-income and middle-income countries. We analysed data from five long-standing prospective cohort studies from Brazil, Guatemala, India, the Philippines, and South Africa and noted that indices of maternal and child undernutrition (maternal height, birthweight, intrauterine growth restriction, and weight, height, and body-mass index at 2 years according to the new WHO growth standards) were related to adult outcomes (height, schooling, income or assets, offspring birthweight, body-mass index, glucose concentrations, blood pressure). We undertook systematic reviews of studies from low-income and middle-income countries for these outcomes and for indicators related to blood lipids, cardiovascular disease, lung and immune function, cancers, osteoporosis, and mental illness. Undernutrition was strongly associated, both in the review of published work and in new analyses, with shorter adult height, less schooling, reduced economic productivity, and--for women--lower offspring birthweight. Associations with adult disease indicators were not so clear-cut. Increased size at birth and in childhood were positively associated with adult body-mass index and to a lesser extent with blood pressure values, but not with blood glucose concentrations. In our new analyses and in published work, lower birthweight and undernutrition in childhood were risk factors for high glucose concentrations, blood pressure, and harmful lipid profiles once adult body-mass index and height were adjusted for, suggesting that rapid postnatal weight gain--especially after infancy--is linked to these conditions. The review of published works indicates that there is insufficient information about long-term changes in immune function, blood lipids, or osteoporosis indicators. Birthweight is positively associated with lung function and with the incidence of some cancers, and undernutrition could be associated with mental illness. We noted that height-for-age at 2 years was the best predictor of human capital and that undernutrition is associated with lower human capital. We conclude that damage suffered in early life leads to permanent impairment, and might also affect future generations. Its prevention will probably bring about important health, educational, and economic benefits. Chronic diseases are especially common in undernourished children who experience rapid weight gain after infancy.

Fetal growth and childhood cholesterol levels in the United States

Research has linked fetal environment to subsequent adult disease. This study examines the extent to which infants born small-for-gestational age (SGA) were at risk for high cholesterol levels in early childhood (ages 4-6 years). Data were obtained from 1727 children aged 4-6 years who participated in the cross-sectional third US National Health and Nutrition Examination Survey and had both birth certificates and blood cholesterol information. The odds of having moderately elevated (170-199 mg/dL) or high (> or =200 mg/dL) serum total cholesterol after being born SGA were determined after controlling for sex, race/ethnicity, education of household head, saturated fat intake, parental history of high cholesterol and overweight status. Approximately 11% of participants were SGA. Proportions of children with moderately elevated and high cholesterol levels were approximately 28 and 8%, respectively. SGA children were almost twice as likely (odds ratio 1.97, 95% confidence interval [0.8, 4.8]) to have high cholesterol vs. low cholesterol than non-SGA children, although the result was not statistically significant. Multiple linear regression demonstrated a similar inverse, non-significant relationship between gestation-adjusted birthweight and cholesterol (beta = -2.3, P = 0.33). These data indicate a possible association between reduced fetal growth, represented by birthweight adjusted for gestational age, and increased cholesterol levels in early childhood.

Sex differences in the associations between birthweight and lipid levels in middle-age: findings from the 1958 British birth cohort

OBJECTIVE

To examine sex differences in birthweight-lipid associations.

METHODS AND RESULTS

Using prospectively collected data on birthweight and non-fasting lipid levels at age 44-45 y from the 1958 British birth cohort (3603 men and 3583 women), sex differences in birthweight-lipid associations were examined. There were inverse associations between birthweight and total and low-density-lipoprotein (LDL)-cholesterol among women (a 1 kg increase in birthweight was associated with a 0.13 mmol/L reduction in total cholesterol (p<0.001) and a 0.07 mmol/L reduction in LDL-cholesterol (p=0.02)) but no associations among men (p=0.005 and p=0.01, respectively, for birthweight x sex interactions). There was an inverse association between birthweight and triglycerides of a similar magnitude in both sexes (a 1 kg increase in birthweight was associated with a 7% reduction in triglyceride levels in sex-adjusted models (p<0.001)). There was no association between birthweight and high-density-lipoprotein-cholesterol. Associations were largely unaltered after adjustment for covariates. Of birthweight, current height and BMI, the latter was the strongest predictor of lipid levels.

CONCLUSIONS

The finding of an inverse association between birthweight and triglycerides in both sexes and of inverse associations between birthweight and total and LDL-cholesterol only in women suggests that the mechanisms underlying the associations with birthweight may vary for different lipids.

Fetal nutrition and adult hypertension, diabetes, obesity, and coronary artery disease

The fetal-origins-of-adult-disease hypothesis describes an adaptive phenomenon of in utero reprogramming of the undernourished fetus that predisposes the infant to increased morbidity as an adult. Studies have identified a positive association between indicators of fetal undernutrition such as low birth weight and chronic adult diseases like hypertension, diabetes, obesity, and coronary artery disease. Current research is focusing on determining other factors that may contribute to these chronic adult diseases.

Obesity and cardiovascular disease

Background

The prevalence of obesity has reached epidemic proportions, and in terms of the extent of its negative impact on the health has been compared to those of tobacco and alcohol. One of the first medical consequences of obesity to be recognised was cardiovascular disease (CVD). Obesity, particularly abdominal obesity, predisposes a person to a number of other cardiovascular risk factors, and is an independent predictor of clinical CVD including coronary death, coronary heart disease, heart failure and stroke.

Materials and methods

A Medline search using the following keywords (obesity, cardiovascular disease, body mass index, cardiovascular risk factors, type 2 diabetes, metabolic syndrome) was performed looking for high impact factor English-written references.

Results

Ninety-nine (N=99) relevant articles published in the last 15 years were selected and commented. As detailed throughout the text, current therapies available for weight management can improve or prevent many of these obesity-related risk factors for CVD. However, there is some controversy as to whether weight loss is beneficial for health, and large clinical outcome trials such as the Look-AHEAD (Action for Health in Diabetes) trial or the SCOUT (Sibutramine Cardiovascular Outcomes Trial) study are currently ongoing.

Discussion

In the present review, we summarise the effects of obesity as well as the efficacy of weight-loss interventions on cardiovascular risk factors and CVD.

Birth weight correlates differently with cardiovascular risk factors in youth

OBJECTIVE

Childhood obesity has become prevalent, resulting in a greater risk of hypertension, diabetes, and dyslipidemia. However, the relationship between these comorbid conditions and birth weight remains uncertain. We conducted this study to evaluate the relationship between birth weight and cardiovascular risk factors in children and adolescents.

RESEARCH METHODS AND PROCEDURES

In a nationwide survey conducted between 1992 and 2000, all schoolchildren 6 to 18 years old with glucosuria, proteinuria, or microscopic hematuria in repeated urine samples were included and received a physical examination and blood test. Those with gestational age <37 weeks were excluded. We enrolled 81,538 children (51,111 girls and 30,427 boys) and obtained their birth weights from the Taiwan Birth Registry. Obesity and hypertension were defined by age- and sex-specific cut-offs. Diabetes was diagnosed if the fasting glucose was >7 mM.

RESULTS

The risk of obesity was higher for those with birth weights > or =4000 grams [odds ratio (OR), 1.65] and 3543 to 3999 grams (OR, 1.28) and lower for those with birth weights 2601 to 2999 grams (OR, 0.90), using 3000 to 3542 grams as the reference group. An increased risk of diabetes was associated with both higher and lower birth weights, indicating a U-shaped relationship (OR, <2600 grams, 1.607; 2601 to 2999 grams, 1.119; 3543 to 3999 grams, 1.112; > or =4000 grams, 1.661). In the 10- to 12-year-old age group, the risk of hypertension was higher in those with birth weights <2600 grams (OR, 1.20).

DISCUSSION

Low birth weight was associated with childhood diabetes. High birth weight was correlated with childhood obesity and diabetes. Our data indicate different relationships between birth weight and the development of obesity, hypertension, and diabetes in childhood.

Life course body size and lipid levels at 53 years in a British birth cohort

OBJECTIVES

To investigate the association between growth in height and change in body mass index (BMI) during the life course on lipid levels at 53 years.

METHODS

2311 men and women from a British cohort study were included in analyses. Non-fasting total, high-density lipoprotein (HDL) and low-density lipoprotein (LDL) cholesterol levels were measured at 53 years. Height and BMI at 2, 4, 7, 11, 15 and 36 years in relation to the lipid outcomes at 53 years were assessed using multiple regression models. The effects of z scores of height and BMI at 2 years and yearly rates of change (velocities) in height and BMI between 2-7, 7-15 and 15-36 years were also considered.

RESULTS

Total cholesterol level decreased by 0.119 mmol/l (95% CI -0.194 to -0.045) per SD increase in height at 2 years and by 0.073 mmol/l (95% CI -0.145 to -0.001) for every SD increase in height velocity between 15 years and adulthood. Similar, but weaker associations were seen for LDL cholesterol. The relationships between leg length and total and LDL cholesterol were stronger than the relationship with trunk length. Higher BMI at 36 and 53 years and greater BMI increases between 15-36 and 36-53 years were associated with higher total and LDL cholesterol and lower HDL cholesterol levels. The effects of growth could not be explained by birth weight or lifetime socioeconomic status.

CONCLUSIONS

Early life exposures, which restrict height growth in infancy, resulting in shorter adult leg length, may influence lipid levels in adult life.

Is birth weight a risk factor for ischemic heart disease in later life?

BACKGROUND

An inverse association between birth weight and ischemic heart disease (IHD) has been seen in observational studies.

OBJECTIVE

We wanted to determine the strength and consistency of the association between birth weight and subsequent IHD.

DESIGN

We conducted a systematic review of observational studies.

RESULTS

Seventeen published studies of birth weight and subsequent IHD were identified that included a total of 144,794 singletons. Relative risk estimates for the association between birth weight and IHD were available from 16 of these studies. Additional data from 2 unpublished studies of 3801 persons were also included. In total, the analyses included data from 18 studies on 4210 nonfatal and 3308 fatal IHD events in 147,009 persons. The mean weighted estimate for the association between birth weight and the combined outcome of nonfatal and fatal IHD was 0.84 (95% CI: 0.81, 0.88) per kilogram of birth weight (P<0.0001). No significant heterogeneity was observed between estimates in different studies (P=0.09), nor was there evidence of publication bias (P=0.3, Begg test). Neither restricting the analysis to fatal IHD events nor adjusting for socioeconomic status had any appreciable effect on the findings.

CONCLUSIONS

These findings are consistent with a 1 kg higher birth weight being associated with a 10-20% lower risk of subsequent IHD. However, even if causal, interventions to increase birth weight are unlikely to reduce the incidence of IHD materially. Further studies are needed to determine whether the observed association reflects a stronger underlying association with a related exposure or is due (at least in part) to residual confounding.

The influence of birth weight and genetic factors on lipid levels: a study in adult twins

Twins can be used to investigate the biological basis for observed associations between birth weight and later disease risk, as they experiencein uterogrowth restriction compared with singletons, which can differ in magnitude within twin pairs despite partial or total genetic identity. In the present study, sixty monozygotic and seventy-one dizygotic same-sex twin pairs aged 19–50 years and eighty-nine singleton controls matched for age, gestational age, sex, maternal age and parity were recruited from an obstetric database. Associations between fasting lipid levels and birth weight were assessed by linear regression with adjustment for possible confounding factors. Twins were significantly lighter at birth but were not significantly different in adult height, weight or lipid levels from the singleton controls. There was a significant inverse association between birth weight and both total and LDL-cholesterol levels among singleton controls (−0·53mmol/l per kg (95% CI −0·97, −0·09),P=0·02 and −0·39mmol/l per kg (95% CI −0·76, −0·02),P=0·04, respectively), but there was no significant association between birth weight and lipid levels in either unpaired or within-pair analysis of twins. The results suggest that thein uterogrowth restriction and early catch-up growth experienced by twins does not increase the risk of an atherogenic lipid profile in adult life.

Intrauterine, Environmental, and Genetic Influences in the Relationship Between Birth Weight and Lipids in a Female Twin Cohort

Objective— To investigate the association between birth weight and lipid levels in a cohort of UK female twins.

Methods and Results— Birth weights and fasting blood lipid levels were available for 2900 women aged 18 to 80 years. Individual level regressions indicated that a 1-kg increase in birth weight was associated with a 0.08-mmol/L decrease in total cholesterol (95% confidence interval [CI], −0.12, −0.04) and a 0.06-mmol/L decrease in low-density lipoprotein (−0.10, −0.03). Using a regression model that includes both mean twin pair birth weight and individual twin’s difference from the pair mean, we found that these significant relationships were between twin pairs only and not within pairs. We found no significant relationships for high-density lipoprotein. When monozygotic and dizygotic twins were analyzed separately we found similar effect sizes. Restricting the analysis to postmenopausal women we found stronger relationships between birth weight and lipid levels, which was attenuated after adjustment for body mass index (BMI).

Conclusions— These novel results suggest that significant relationships between birth weight and lipids are mediated through shared influences on the maternal environment and do not support the hypothesis that fetal malnutrition is an important determinant of adult lipid levels. Adjustment for BMI also indicates that postnatal growth may be more important than prenatal growth.

A study of TH01 and IGF2-INS-TH haplotypes in relation to smoking initiation in three independent surveys

OBJECTIVES

Recent studies suggest an association between a microsatellite locus (TH01) located in intron 1 of the tyrosine hydroxylase gene (TH) and nicotine dependence. We aimed here to study whether both TH01 and haplotypes of the wider IGF2-INS-TH region influence initiation of regular smoking in current smokers.

METHODS

A total of 3637 individuals from three independent studies (two of adults and one of adolescents) were analysed in relation to the age of first regular smoking (AFRS). Haplotypes and genotypes were obtained for the polymorphisms TH01, IGF2 ApaI, INS HphI and DRD4 VNTR (48 bp)n. Association between IGF2-INS-TH haplotypes and AFRS was tested by a regression model. A genotype-based genetic model assuming additivity was followed in order to estimate the effect of individual loci.

RESULTS

Overall, no significant associations were found after correcting for multiple tests. However, an IGF2-INS-TH haplotype (*5) was found to be nominally associated with AFRS at younger ages in adult smokers. Analyses of individual loci points to TH01 as a possible candidate influencing initiation of regular smoking. An AFRS-lowering trend nominally associated with allele 9 in a dosage-dependent manner was identified in both adult cohorts. TH01 did not show association or trend with age of initiation (first puff) either in adolescents or in the adolescents smoking regularly at age 18.

CONCLUSION

This study adds to the genetic evaluation of the associations of TH01 with smoking predisposition. Differences between historical and prospective surveys, different biological pathways and possible functional roles of this microsatellite in smoking initiation are discussed.