Adjustment For Current Weight Research Articles

Small for date preterm infants and risk of higher blood pressure in later life: A systematic review and meta-analysis.

Historical reports suggest that infants born small for gestational age (SGA) are at increased risk for high blood pressure (BP) at older ages after adjustment for later age body size. Such adjustment may be inappropriate since adiposity is a known cause of cardiovascular and metabolic disease. To assess the association between SGA births and later BP among preterm births, considering potential background confounders and over-adjustment for later body size. A database search of studies up to October 2022 included MEDLINE, EMBASE and CINAHL. Studies were included if they reported BP (systolic [SBP] or diastolic [DBP]) (outcomes) for participants born preterm with SGA (exposure) or non-SGA births. All screening, extraction steps, and risk of bias (using the Risk of Bias In Non-randomised Studies of Interventions [ROBINS-I] tool) were conducted in duplicate by two reviewers. Data were pooled in meta-analysis using random-effects models. We explored potential sources of heterogeneity. We found no meaningful difference in later BP between preterm infants with and without SGA status at birth. Meta-analysis of 25 studies showed that preterm SGA, compared to preterm non-SGA, was not associated with higher BP at age 2 and older with mean differences for SBP 0.01 mmHg (95% CI -0.10, 0.12, I2 = 59.8%, n= 20,462) and DBP 0.01 mm Hg (95% CI -0.10, 0.12), 22 studies, (I2 = 53.0%, n= 20,182). Adjustment for current weight did not alter the results, which could be due to the lack of differences in later weight status in most of the included studies. The included studies were rated to be at risk of bias due to potential residual confounding, with a low risk of bias in other domains. Evidence indicates that preterm infants born SGA are not at increased risk of developing higher BP as children or as adults as compared to non-SGA preterm infants.

Weight Trajectories from Birth and Bone Mineralization at 7 Years of Age

To assess whether different trajectories of weight gain since birth influence bone mineral content (BMC) and areal bone mineral density (aBMD) at 7 years of age. We studied a subsample of 1889 children from the Generation XXI birth cohort who underwent whole-body dual-energy radiograph absorptiometry. Weight trajectories identified through normal mixture modeling for model-based clustering and labeled "normal weight gain," "weight gain during infancy," "weight gain during childhood," and "persistent weight gain" were used. Differences in subtotal BMC, aBMD, and size-corrected BMC (scBMC) at age 7 years according to weight trajectories were estimated through analysis of covariance. Compared with the "normal weight gain" trajectory, children in the remaining trajectories had significantly greater BMC, aBMD, and scBMC at age 7 years, with the strongest associations for "persistent weight gain" (girls [BMC: 674.0 vs 559.8 g, aBMD: 0.677 vs 0.588 g/cm2, scBMC: 640.7 vs 577.4 g], boys [BMC: 689.4 vs 580.8 g, aBMD: 0.682 vs 0.611 g/cm2, scBMC: 633.0 vs 595.6 g]). After adjustment for current weight, and alternatively for fat and lean mass, children with a "weight gain during childhood" trajectory had greater BMC and aBMD than those with a "normal weight gain" trajectory, although significant differences were restricted to girls (BMC: 601.4 vs 589.2 g, aBMD: 0.618 vs 0.609 g/cm2). Overall, children following a trajectory of persistent weight gain since birth had clearly increased bone mass at 7 years, but weight gain seemed slightly more beneficial when it occurred later rather than on a normal trajectory during the first 7 years of life.

Lower birth weight is associated with alterations in dietary intake in adolescents independent of genetic factors: A twin study

Lower birth weight is associated with an increased risk of cardiovascular and metabolic disease. These associations may, at least in part, be explained by alterations in dietary intake in later life. The aim of this study is to examine whether lower birth weight is associated with alterations in dietary intake in later life, and whether this association is due to intrauterine environmental or genetic factors. In this observational study birth weight and dietary intake were investigated in 78 dizygotic (DZ) and 94 monozygotic (MZ) adolescent same-sex twin subjects. Birth weight was obtained from the mothers. Dietary intake was assessed by two-day dietary records. In the total group of twins, lower birth weight was associated with higher intake of saturated fat after adjustment for current weight (1.2 per cent of total energy intake (E%) per kg increase in birth weight, P<0.01). Intra-pair analysis in all twin pairs demonstrated that twins with the lower birth weight had a 115kcal higher total energy intake and a 0.7 E% higher saturated fat intake compared to their co-twins with the higher birth weight (P<0.05). Intra-pair differences in birth weight were negatively associated with differences in energy intake and differences in intake of saturated fat after adjustment for differences in current weight (P=0.07 and P<0.05, respectively). Intra-pair differences in birth weight were positively associated with intra-pair differences in intake of dietary fibres (P<0.05). These intra-pair differences and associations were similar for DZ and MZ twins (P for difference>0.6). Lower birth weight was related with higher intake of energy and saturated fat within twin pairs, and these associations were independent of zygosity, suggesting that the association between birth weight and alterations in dietary intake in later life is explained by intrauterine environmental rather than genetic factors.

Re: "Assessing the Possible Direct Effect of Birth Weight on Childhood Blood Pressure: A Sensitivity Analysis"

In a recent article, Chiolero et al. confirmed that the association between birth weight and blood pressure is strengthened upon adjustment for current weight. This phenomenon has been consistently reported in the literature, but its interpretation is still debatable. I would like to ask the following question. Are those estimates useful for predicting future blood pressure or for informing us about the magnitude of blood pressure reduction with a successful birth-weight gain?

Assessing the Possible Direct Effect of Birth Weight on Childhood Blood Pressure: A Sensitivity Analysis

To estimate the possible direct effect of birth weight on blood pressure, it is conventional to condition on the mediator, current weight. Such conditioning can induce bias. Our aim was to assess the potential biasing effect of U, an unmeasured common cause of current weight and blood pressure, on the estimate of the controlled direct effect of birth weight on blood pressure, with the help of sensitivity analyses. We used data from a school-based study conducted in Switzerland in 2005-2006 (n = 3,762; mean age = 12.3 years). A small negative association was observed between birth weight and systolic blood pressure (linear regression coefficient βbw = -0.3 mmHg/kg, 95% confidence interval: -0.9, 0.3). The association was strengthened upon adjustment for current weight (βbw|C = -1.5 mmHg/kg, 95% confidence interval: -2.1, -0.9). Sensitivity analyses revealed that the negative conditional association was explained by U only if U was relatively strongly associated with blood pressure and if there was a large difference in the prevalence of U between low-birth weight and normal-birth weight children. This weakens the hypothesis that the negative relationship between birth weight and blood pressure arises only from collider-stratification bias induced by conditioning on current weight.

Why adjustment for current weight can bias the estimate of the effect of birth weight on blood pressure

aIUMSP, University of Lausanne, Switzerland bDepartment of Epidemiology, Biostatistics and Occupational Health, McGill University, Montreal, Canada Correspondence to Arnaud Chiolero, MD, PhD, Institute of social and preventive medicine (IUMSP), Lausanne University Hospital, Biopôle 1, 1066 Epalinges, Switzerland. Tel: +41 21 314 72 72; fax: +41 21 314 73 73; e-mail: [email protected] Received 25 January, 2012 Accepted 9 February, 2012

Birth weight, weight change, and blood pressure during childhood and adolescence

We assessed the association between birth weight, weight change, and current blood pressure (BP) across the entire age-span of childhood and adolescence in large school-based cohorts in the Seychelles, an island state in the African region. Three cohorts were analyzed: 1004 children examined at age 5.5 and 9.1 years, 1886 children at 9.1 and 12.5, and 1575 children at 12.5 and 15.5, respectively. Birth and 1-year anthropometric data were gathered from medical files. The outcome was BP at age 5.5, 9.1, 12.5 or 15.5 years, respectively. Conditional linear regression analysis was used to estimate the relative contribution of changes in weight (expressed in z-score) during different age periods on BP. All analyses were adjusted for height. At all ages, current BP was strongly associated with current weight. Birth weight was not significantly associated with current BP. Upon adjustment for current weight, the association between birth weight and current BP tended to become negative. Conditional linear regression analyses indicated that changes in weight during successive age periods since birth contributed substantially to current BP at all ages. The strength of the association between weight change and current BP increased throughout successive age periods. Weight changes during any age period since birth have substantial impact on BP during childhood and adolescence, with BP being more responsive to recent than earlier weight changes.

The effect of feto-maternal size and childhood growth on left ventricular mass and arterial stiffness in Afro-Caribbean children

We hypothesized that maternal size, fetal size and childhood growth are associated with childhood blood pressure, left ventricular mass (LVM) and arterial stiffness. The Vulnerable Windows Cohort is a longitudinal study of 569 mothers and their offspring. Anthropometry was measured on each child at birth, at 6 weeks, once in 3 months upto 2 years and then every 6 months. Blood pressure and body composition were assessed in 185 children (age 11.5 years) and echocardiography performed. LVM was not associated with maternal size after adjustment for child's weight. LVM was significantly associated with faster growth in childhood and with current weight, fat mass and lean mass. Systolic blood pressure was not related to maternal, fetal or newborn anthropometry, but was positively associated with infant and childhood growth, as well as current body size and fat mass. The pulse pressure/stroke volume ratio (an index of arterial stiffness) was inversely associated with maternal size, placental volume at 20 weeks, fetal size at 35 weeks and childhood growth even after adjustment for current weight. In conclusion, LVM in childhood is positively associated with maternal height, child's current size and rate of growth. Arterial stiffness is inversely related to maternal, fetal and placental size as well as growth throughout childhood.

Tracking and determinants of subcutaneous fat mass in early childhood: the Generation R Study

To examine the development and tracking of subcutaneous fat mass in the first 2 years of life and to examine which parental, fetal and postnatal characteristics are associated with subcutaneous fat mass. This study was embedded in the Generation R Study, a prospective cohort study from early fetal life onward. Subcutaneous fat mass was measured by skinfold thickness (biceps, triceps, suprailiacal, subscapular) at the ages of 1.5, 6 and 24 months in 1012 children. Information about parental, fetal and postnatal growth characteristics was collected by physical and fetal ultrasound examinations and questionnaires. Normal values of subcutaneous fat mass are presented. Total subcutaneous fat mass was higher in girls than in boys at the age of 24 months (P=0.01). Subjects in the lowest and highest quartiles at the age of 6 months tended to keep their position in the same quartile at the age of 24 months (odds ratios 1.86 (95% confidence interval (CI) 1.3, 2.7)) and 1.84 (95% CI: 1.3, 2.6), respectively). Maternal height and weight, paternal weight, fetal weight at 30 weeks, birth weight and weight at the age of 6 weeks were each inversely associated with subcutaneous fat mass at the age of 24 months after adjustment for current weight at 24 months. This study shows for the first time that subcutaneous fat mass tends to track in the first 2 years of life. Furthermore, the results suggest that an adverse fetal environment and growth are associated with increased subcutaneous fat mass at the age of 24 months. Further studies are needed to examine whether these associations persist in later life.

Growth hormone binding protein levels in children are associated with birth weight, postnatal weight gain, and insulin secretion

Rapid infancy weight gain is associated with subsequent higher circulating insulin-like growth factor (IGF) I levels in normal children. We hypothesized that circulating levels of growth hormone binding protein (GHBP), a putative marker of GH sensitivity, may also be associated with postnatal weight gain and insulin secretion. In 751 normal children aged 7 to 8 years, we measured insulin, glucose, GHBP, IGF-I, IGF binding protein (IGFBP) 1, and IGFBP-3 levels in a fasting venous blood sample. Insulin secretion was assessed by measuring insulin and glucose levels 30 minutes after an oral glucose load. After adjustment for current weight, birth weight was inversely related to IGF-I and GHBP levels. Children with lower birth weight and rapid weight gain between birth and 3 years had higher IGF-I and GHBP levels and also lower IGFBP-1 levels than other children. Allowing for current body mass index, GHBP levels were positively related to insulin secretion. In conclusion, children who showed rapid early postnatal weight gain after low birth weight have higher levels of GHBP than other children. Increased GH sensitivity in such children could contribute to links between rapid infancy weight gain and subsequent faster rates of childhood growth and maturation.

Substrate-energy metabolism and metabolic risk factors for cardiovascular disease in relation to fetal growth and adult body composition

The effect of fetal programming on intermediary metabolism is uncertain. Therefore, we examined whether fetal programming affects oxidative and nonoxidative macronutrient metabolism and the prevalence of the metabolic syndrome in adult life. Healthy older men, aged 64-72 years, with either a lower birth weight (LBW, <or=25th %ile; n = 16) or higher birth weight (HBW, >or=75th %ile; n = 13) had measurements of 1) net oxidative metabolism using indirect calorimetry before and for 6 h after a mixed meal (3,720 kJ) and 2) postprandial oxidation of exogenous [13C]palmitic acid. Body composition was measured using dual-energy X-ray absorptiometry. After adjustment for current weight and height, the LBW group had a lower resting energy expenditure (REE) in the preprandial (4.01 vs. 4.54 kJ/min, P = 0.015) and postprandial state (4.60 vs. 5.20 kJ/min, P = 0.004), and less fat-free mass than the HBW group. The BW category was a significant, independent, and better predictor of REE than weight plus height. There were no significant differences between groups in net oxidative and nonoxidative macronutrient (protein, fat, carbohydrate) metabolism (or of exogenous [13C]palmitate) or in the prevalence of the metabolic syndrome, which was present almost twice as commonly in the LBW than in the HBW group. The study suggests that fetal programming affects both pre- and postprandial EE in older life by mechanisms that are at least partly related to the mass of the fat-free body. BW was found to be a significant predictor of REE that was independent of adult weight plus height.

RE: “WHY EVIDENCE FOR THE FETAL ORIGINS OF ADULT DISEASE MIGHT BE A STATISTICAL ARTIFACT: THE ‘REVERSAL PARADOX’ FOR THE RELATION BETWEEN BIRTH WEIGHT AND BLOOD PRESSURE IN LATER LIFE”

Some researchers have recently questioned the validity of associations between birth weight and health in later life. They argue that these associations might be due in part to inappropriate statistical adjustment for variables on the causal pathway (such as current body size), which creates an artifactual statistical effect known as the “reversal paradox.” Computer simulations were conducted for three hypothetical relations between birth weight and adult blood pressure. The authors examined the effect of statistically adjusting for different correlations between current weight and birth weight and between current weight and adult blood pressure to assess their impact on associations between birth weight and blood pressure. When there was no genuine relation between birth weight and blood pressure, adjustment for current weight created an inverse association whose size depended on the magnitude of the positive correlations between current weight and birth weight and between current weight and blood pressure. When there was a genuine inverse relation between birth weight and blood pressure, the association was exaggerated following adjustment for current weight, whereas a positive relation between birth weight and blood pressure could be reversed after adjusting for current weight. Thus, researchers must consider the reversal paradox when adjusting for variables that lie within causal pathways. birth weight; blood pressure; computer simulation; confounding factors (epidemiology); statistics

Why Evidence for the Fetal Origins of Adult Disease Might Be a Statistical Artifact: The "Reversal Paradox" for the Relation between Birth Weight and Blood Pressure in Later Life

Some researchers have recently questioned the validity of associations between birth weight and health in later life. They argue that these associations might be due in part to inappropriate statistical adjustment for variables on the causal pathway (such as current body size), which creates an artifactual statistical effect known as the "reversal paradox." Computer simulations were conducted for three hypothetical relations between birth weight and adult blood pressure. The authors examined the effect of statistically adjusting for different correlations between current weight and birth weight and between current weight and adult blood pressure to assess their impact on associations between birth weight and blood pressure. When there was no genuine relation between birth weight and blood pressure, adjustment for current weight created an inverse association whose size depended on the magnitude of the positive correlations between current weight and birth weight and between current weight and blood pressure. When there was a genuine inverse relation between birth weight and blood pressure, the association was exaggerated following adjustment for current weight, whereas a positive relation between birth weight and blood pressure could be reversed after adjusting for current weight. Thus, researchers must consider the reversal paradox when adjusting for variables that lie within causal pathways.

The role of genetic and environmental factors in the association between birthweight and blood pressure: evidence from meta-analysis of twin studies.

An inverse association between birthweight and later blood pressure has been found in many studies in singletons. Twin studies have been used to examine whether genetic factors or family environment could account for this association. A systematic review identified 10 studies covering 3901 twin pairs. Meta-analysis of regression coefficients for the association between birthweight and systolic blood pressure was carried out for unpaired versus paired associations and for paired associations in dizygotic versus monozygotic pairs. After adjustment for current weight or body mass index (BMI), the difference in systolic blood pressure per kg birthweight was -2.0 (95% CI: -3.2, -0.8) mmHg in the unpaired analysis and -0.4 (95% CI: -1.5, 0.7) mmHg in the paired analysis in the same subjects. In the paired analysis by zygosity, in all twins the coefficients were -0.7 (95% CI: -2.3, 0.8) mmHg in dizygotic pairs and -0.8 (95% CI: -2.1, 0.4) mmHg in monozygotic pairs, but in studies which included zygosity tests the coefficients were -1.0 (95% CI: -3.3, 1.6) mmHg in dizygotic pairs and -0.4 (95% CI: -1.9, 1.3) mmHg in monozygotic pairs. The attenuation of the regression coefficient in the paired analysis provides support for the possibility that factors shared by twins contribute to the association between birthweight and blood pressure in singletons. Comparison of paired analysis in monozygotic and dizygotic pairs could not provide conclusive evidence for a role for genetic as opposed to shared environmental factors.

Unravelling the fetal origins hypothesis: is there really an inverse association between birthweight and subsequent blood pressure?

The association between birthweight and subsequent blood pressure levels has been considered to provide some of the strongest, and most consistent, support for the "fetal origins" hypothesis of adult disease. It had been estimated that a 1 kg higher birthweight is typically associated with a 2-4 mm Hg lower systolic blood pressure. 55 studies that had reported regression coefficients of systolic blood pressure on birthweight (with 48 further studies that reported only the direction of this association), and seven such studies within twin pairs, were identified. Each study was weighted according to the inverse of the variance of the regression coefficient (ie, "statistical size"), and combined using a "fixed effects" approach. Among the 55 studies that reported regression coefficients, there was a clear trend (p<0.0001) towards weaker associations in the larger studies: -1.9 mm Hg/kg in those with less than about 1000 participants; -1.5 mm Hg/kg with about 1000-3000 participants; and -0.6 mm Hg/kg with more than 3000 participants. By contrast with the inverse associations reported in 52 of these 55 studies, only 25 of the 48 studies that did not report regression coefficients found an inverse association (p<0.0001 for heterogeneity). Almost all of these regression coefficients had been adjusted for current weight (whereas few were adjusted for potential confounding factors), and removal of this adjustment in the larger studies reduced the estimated association to -0.4 mm Hg/kg. For studies within monozygotic twin pairs, the combined estimate was -0.6 mm Hg/kg with adjustment for current weight, and was also reduced without this adjustment. Claims of a strong inverse association between birthweight and subsequent blood pressure may chiefly reflect the impact of random error, selective emphasis of particular results, and inappropriate adjustment for current weight and for confounding factors. These findings suggest that birthweight is of little relevance to blood pressure levels in later life.

The effects of birth weight and postnatal linear growth retardation on blood pressure at age 11–12 years

STUDY OBJECTIVETo determine the effects of birth weight and linear growth retardation (stunting) in early childhood on blood pressure at age 11–12 years.DESIGNProspective cohort study.SETTINGKingston, Jamaica.PARTICIPANTS112 stunted children (height for...

Birth weight, childhood growth, and cardiovascular disease risk factors in Japanese aged 20 years.

To determine whether birth weight and childhood growth, especially rate of height increase, are independently related to major cardiovascular disease risk factors in adult life, the authors conducted a 20-year follow-up study in a Japanese population, using the record-linkage method. From medical checkup data for babies and for residents aged 20 years in Ishikawa, Japan, the authors obtained 20-year follow-up data (1985-1994) on 4,626 participants (2,198 men and 2,428 women) born in 1965-1974. Using multiple linear regression analysis, the authors estimated that a 1-standard-deviation higher birth weight was significantly associated with systolic blood pressure that was lower by 1.6 mmHg in men and by 1.0 mmHg in women, and with a serum cholesterol level that was lower by 0.07 mmol/liter in men and by 0.04 mmol/liter in women, after adjustment for current weight and rate of height increase. Moreover, after adjustment for birth weight and current weight, a 1-standard-deviation higher rate of height increase from age 3 years to age 20 years was significantly associated with systolic blood pressure that was lower by 0.7 mmHg in men and by 0.5 mmHg in women, and with serum cholesterol that was lower by 0.09 mmol/liter in men and by 0.05 mmol/liter in women. The results suggest that lower birth weight and lower rate of height increase during childhood are independently associated with increases in blood pressure and serum cholesterol in adult life.

Insulin resistance syndrome in 8-year-old Indian children: small at birth, big at 8 years, or both?

We have studied 477 8-year-old Indian children to define the relationship between birth weight and cardiovascular risk factors, including insulin resistance syndrome (IRS) variables and plasma total and LDL cholesterol concentrations. All risk factors were strongly related to current weight. After adjustment for current weight, age, and sex, lower birth weight was associated with higher systolic blood pressure (P = 0.008), fasting plasma insulin and 32-33 split proinsulin concentrations (P = 0.08 and 0.02), glucose and insulin concentrations 30 min postglucose (P = 0.06 and 0.04), subscapular/triceps skinfold ratio (P = 0.003), and plasma total and LDL cholesterol concentrations (P = 0.002 and 0.001). Lower birth weight was associated with increased calculated insulin resistance (homeostasis model assessment [HOMA], P = 0.03), but was not related to the HOMA index of beta-cell function. The highest levels of IRS variables and total and LDL cholesterol were in children of low birth weight but high fat mass at 8 years. Taller height at 8 years predicted higher fasting plasma insulin concentrations, insulin resistance, and plasma total and LDL cholesterol concentrations. The most insulin-resistant children were those who had short parents but had themselves grown tall. Although the implications of our findings in relation to height are unclear, interventions to improve fetal growth and to control obesity in childhood are likely to be important factors in the prevention of cardiovascular disease and IRS in India.

Birthweight and blood pressure among children in Harare, Zimbabwe

AIMTo determine whether poor uterine growth may be associated with increased blood pressure and subsequent hypertension in adulthood.METHODSA retrospective cohort study of 756 schoolchildren (mean age 6.5 years) was carried...