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

The developmental origins of chronic adult disease

Low birthweight is now known to be associated with increased rates of coronary heart disease and the related disorders stroke, hypertension and non-insulin-dependent diabetes. These associations have been extensively replicated in studies in different countries and are not the result of confounding variables. They extend across the normal range of birthweight and depend on lower birthweights in relation to the duration of gestation rather than the effects of premature birth. The associations are thought to be consequences of developmental plasticity, the phenomenon by which one genotype can give rise to a range of different physiological or morphological states in response to different environmental conditions during development. Recent observations have shown that impaired growth in infancy and rapid childhood weight gain exacerbate the effects of impaired prenatal growth. Coronary heart disease and the disorders related to it arise through a series of interactions between environmental influences and the pathways of development that preceded them. These diseases are the product of branching pathways of development in which the branchings are triggered by the environment before and after birth.

Hypertension research in the 21st century

This paper presents a signpost for hypertension research, emphasizing areas most likely to yield major clinical and public health benefits. Specific questions are posed in the context of fetal and maternal precursors of cardiovascular disease, vascular biology, resistant hypertension, antihypertensive drugs, primary aldosteronism, lifestyle and genetic interactions and translational research. Worldwide increasing rates of obesity and diabetes demonstrate the need for a global approach to cardiovascular risk and the need for more effective use of existing knowledge. Equal emphasis is given to the critical importance of the fundamental research required to defeat hypertensive cardiovascular disease in the long run.

Fetal and childhood onset of adult cardiovascular diseases

Childhood onset of adult cardiovascular disease has become a significant public health problem. Whether genetic, environmental, or fetal influences are the primary culprits in the epidemic of the cardiovascular disease seen today remains unknown. The benefits of an overall physically active lifestyle that includes weight control, lower blood pressure, avoidance of tobacco use, and consistent exercise are clear and can impact the overall health of children and adolescents. Physicians who care for children and adolescents must begin to incorporate screening of adult cardiovascular disorders into their practice. Better understanding of the etiology of these disease states will bring with it enhanced preventive and targeted therapies.

Birth weight and blood pressure in childhood: results from the Health Survey for England

Findings of previous reports relating low birth weight with raised blood pressure in childhood and adolescence have been inconsistent. The present study uses cross-sectional data from a series of nationally representative annual surveys--the Health Survey for England--between 1995 and 2002, totaling a sample of 15 629 children aged 5 to 15. A significant negative relationship between birth weight, in quartiles or dichotomized as low (<2.5 kg) and normal (> or =2.5 kg) and systolic blood pressure was apparent. Linear regression analyses confirmed these findings. When current weight was included in the model, the strength of the relationship increased. An interaction term between birth weight and current weight was not significant. A life-course plot for those aged 13 to 15 (n=3900), converting the weight measurements at birth and as a teenager to standard deviation scores to make the regression coefficients comparable, showed the importance of weight gain on blood pressure (1 standard deviation increase in weight from birth to age 13 to 15 was associated with an increase in systolic blood pressure of 0.8 mm Hg). Separating those with low and normal birth weight demonstrated that the increase in weight from birth to adolescence had an effect on blood pressure in both those with low and normal birth weight. Postnatal changes in size have a more important effect on blood pressure in childhood and adolescence than birth weight. Reducing the prevalence of overweight among children may reduce their systolic blood pressure importantly and, particularly among children with lower birth weight, the prevalence of hypertension later in life.

Life-long echoes--a critical analysis of the developmental origins of adult disease model

The hypothesis that there is a developmental component to subsequent adult disease initially arose from epidemiological findings relating birth size to either indices of disease risk or actual disease prevalence in later life. While components of the epidemiological analyses have been challenged, there is strong evidence that developmental factors contribute to the later risk of metabolic disease--including insulin resistance, obesity, and heart disease--as well as have a broader impact on osteoporosis, depression and schizophrenia. We suggest that disease risk is greater when there is a mismatch between the early developmental environment (i.e., the phase of developmental plasticity) versus that experienced in mature life (i.e., adulthood), and that nutritional influences are particularly important. It is also critical to distinguish between those factors acting during the developmental phase that disrupt development from those influences that are less extreme and act through regulated processes of epigenetic change. A model of the relationship between the developmental and mature environment is proposed and suggests interventional strategies that will vary in different population settings.

Low birth weight and longitudinal trends of cardiovascular risk factor variables from childhood to adolescence: the bogalusa heart study

Background

Several studies have linked low birth weight to adverse levels of cardiovascular risk factors and related diseases. However, information is sparse at a community level in the U.S. general population regarding the effects of low birth weight on the longitudinal trends in cardiovascular risk factor variables measured concurrently from childhood to adolescence.

Methods

Longitudinal analysis was performed retrospectively on data collected from the Bogalusa Heart Study cohort (n = 1141; 57% white, 43% black) followed from childhood to adolescence by repeated surveys between 1973 and 1996. Subjects were categorized into low birth weight (below the race-specific 10^th percentile; n = 123) and control (between race-specific 50–75^th percentile; n = 296) groups.

Results

Low birth weight group vs control group had lower mean HDL cholesterol (p = 0.05) and higher LDL cholesterol (p = 0.05) during childhood (ages 4–11 years); higher glucose (p = 0.02) during adolescence. Yearly rates of change from childhood to adolescence in systolic blood pressure (p = 0.02), LDL cholesterol (p = 0.05), and glucose (p = 0.07) were faster, and body mass index (p = 0.03) slower among the low birth weight group. In a multivariate analysis, low birth weight was related independently and adversely to longitudinal trends in systolic blood pressure (p = 0.004), triglycerides (p = 0.03), and glucose (p = 0.07), regardless of race or gender. These adverse associations became amplified with age.

Conclusions

Low birth weight is characterized by adverse developmental trends in metabolic and hemodynamic variables during childhood and adolescence; and thus, it may be an early risk factor in this regard.

Naturally occurring intrauterine growth retardation and adult blood pressure in rats

In humans, infants who are born small have been reported to have higher blood pressure in adulthood than do larger infants. This suggests that factors in the intrauterine environment that affect fetal growth can program the individual for hypertension later in life. The present study determined whether there is a similar, naturally occurring relationship between birth weight and adult blood pressure in rats. Female Sprague-Dawley rats bred in our colony were fed a normal diet during pregnancy. On the day of delivery, any pups that weighed <90% of the mean pup weight for the litter were identified as runts. For each runt, a sex-matched littermate of normal weight was also identified and assigned to this study. These pairs were chronically instrumented at approximately 20 wk of age. Mean arterial pressure was significantly higher in runt male and female offspring compared with their normal birth weight littermates (males: 149 +/- 7, runts versus 129 +/- 4 mmHg, controls; females: 128 +/- 1, runts versus 119 +/- 2 mmHg, controls). Although the runts had smaller body weights at study than did their littermate controls, the kidney-to-body weight ratio and renal function normalized to kidney or body weight were not different. These studies indicate that adult blood pressure is related to birth weight in rats, as it is in humans. The relative hypertension in runt animals is not due to gross differences in renal function but may be related to more subtle renal structural and/or functional differences.

Separating within and between effects in family studies: an application to the study of blood pressure in children

In epidemiology the analyses of family or twin studies do not always fully exploit the data, as information on differences between siblings is often used while between-families effect are not considered. We show how cross-sectional time-series linear regression analysis can be easily implemented to estimate within- and between-families effects simultaneously and how these effects can then be compared using the Hausman test. We illustrate this approach with data from the Uppsala family study on blood pressure in children with age ranging from 5.5 to 12.3 years for the younger and from 7.5 to 13.8 years for the older siblings. Comparing the effect of differences in birth weight on blood pressure within-family (in full siblings) and between-families (in unrelated children) allows us to study the contributions of fixed and pregnancy-specific maternal effects on birth weight and consequently on blood pressure. Our data showed a 0.88 mmHg decrease (95 per cent confidence interval: -1.7 to -0.03 mmHg) in systolic blood pressure for one standard deviation increase in birth weight between siblings within a family and 0.88 mmHg (95 per cent confidence interval: -1.6 to -0.2 mmHg) decrease in systolic blood pressure for one standard deviation increase in birth weight between unrelated children. These estimates were controlled for sex, age, pubertal stage, body size and pulse rate of the children at examination and for maternal body size and systolic blood pressure. The within- and between-families effects were not significantly different, p = 0.19, suggesting that fixed and pregnancy-specific factors have similar effects on childhood systolic blood pressure.

Living with the past: evolution, development, and patterns of disease

Epidemiological observations have led to the hypothesis that the risk of developing some chronic noncommunicable diseases in adulthood is influenced not only by genetic and adult life-style factors but also by environmental factors acting in early life. Research in evolutionary biology, developmental biology, and animal and human physiology provides support for this idea and suggests that environmental processes influencing the propensity to disease in adulthood operate during the periconceptual, fetal, and infant phases of life. This "developmental origins of health and disease" concept may have important biological, medical, and socioeconomic implications.

Developmental origins of disease paradigm: a mechanistic and evolutionary perspective

Fetal growth is determined by the interaction between the environment and the fetal genome. The fetal environment, in turn, is determined by the maternal environment and by maternal and placental physiology. There is evidence that the interaction between the fetal environment and genome can determine the risk of postnatal disease, as well as the individual's capacity to cope with the postnatal environment. Furthermore, the role of various forms of maternal constraint of fetal growth in determining the persistence of these responses is reviewed. A limited number of biologic processes can contribute to the mechanistic basis of these phenomena. In addition to immediate homeostatic responses, the developing organism may make predictive adaptive responses of no immediate advantage but with long-term consequences. An evolutionary perspective is provided, as well as a review of possible biologic processes. The "developmental origins of disease" paradigm is a reflection of the persistence of such mechanisms in humans who now live in very different environments from those within which they evolved. The developmental origins paradigm and its underlying mechanistic and evolutionary basis have major implications for addressing the increasing burden of metabolic and cardiovascular disease.

Low birth weight is associated with higher adult total cholesterol concentration in men: findings from an occupational cohort of 25,843 employees

BACKGROUND

The majority of studies investigating the association between birth weight and adult total cholesterol (TC) concentration have been small and underpowered: not surprisingly, the findings have been inconsistent. We aimed to determine whether birth weight predicted adult TC in a large sample population.

METHODS AND RESULTS

Between 1994 and 1996, 132,000 British Telecom employees undertook voluntary occupational health screening. Birth weight and lifestyle factors were self-reported; TC concentration and body size were measured by occupational health nurses. Complete measurements were available for 18,286 men and 7557 women (age range, 17 to 64 years). We found that sex and birth weight significantly interacted to predict adult TC (birth weight/sex interaction term, P=0.002). In men, lower birth weight was associated with higher adult TC levels (a -0.07 reduction in TC for each 1-kg increase in birth weight; 95% CI, -0.09 to -0.04 mmol/L; P<0.001), whereas no association was observed in women. Adjustment for potential confounding factors, including current body size and menopausal status, did not alter the findings. Analysis by SD score showed that in men, a 1-SD decrease in body mass index lowered TC concentration approximately 5-fold more than a 1-SD increase in birth weight.

CONCLUSIONS

This is the largest study to investigate the association between birth weight and TC and suggests that the association may be dependent on sex. The absence of an association in women was not explained by menopausal status. The influence of fetal environment on adult TC is small compared with the influence of adult adiposity.

Trends in blood pressure over 10 years in adolescents: analyses of cross sectional surveys in the Northern Ireland Young Hearts project

OBJECTIVE

To examine secular trends in blood pressure over a 10 year period between two representative cohorts of adolescents from Northern Ireland.

DESIGN

Repeat cross sectional study.

SETTING

Randomly selected post-primary schools from Northern Ireland.

PARTICIPANTS

1015 adolescents studied between 1989 and 1990, and 2017 adolescents studied between 1999 and 2001. Participants were aged 12 or 15 years.

MAIN OUTCOME MEASURES

Systolic and diastolic blood pressure measured by one observer in each study.

RESULTS

The four groups for sex and age showed decreases in both systolic blood pressure (mean decrease 7.7 mm Hg to 10.0 mm Hg) and diastolic blood pressure (8.8 mm Hg to 11.0 mm Hg). These decreases were not accounted for by adjustment for potential confounders including age, height, body mass index, smoking, physical activity, aerobic fitness, and stratification of school by education board area and type. The findings were not altered by additional adjustment for social class, pubertal status, birth weight, and infant feeding. No evidence was found of systematic variation between observers.

CONCLUSIONS

Substantial decreases in systolic and diastolic blood pressure over the past decade in adolescents from Northern Ireland are likely to have important benefits to public health and may help offset the increasing risk of cardiovascular disease due to increases in obesity.

Differential association of birth weight with cardiovascular risk variables in African-Americans and Whites: the Bogalusa heart study

PURPOSE

To study the relationship between low birth weight and the subsequent development of cardiovascular risk factors and to compare this relationship between African-Americans and whites at 7 to 21 years of age.

METHODS

The relationship of birth weight with cardiovascular risk factors, namely, systolic and diastolic blood pressure (BP), BMI, HDL, LDL, triglycerides, and HOMA insulin resistance (HOMA-IR) was examined retrospectively using information on 1155 participants (730 whites and 425 African-Americans) from two cohorts of the Bogalusa Heart Study.

RESULTS

Participants with lower birth weight had higher systolic BP, HOMA-IR, triglycerides, and LDL. The association of birth weight with LDL, triglycerides, and HOMA-IR was stronger in African-Americans, while the association with systolic BP was stronger in whites. Subjects with birth weight <2500 g were at increased risk of having values of HOMA-IR and LDL in the upper quartile of the observed range compared with those with birth weight >2500 g.

CONCLUSIONS

These results support a relationship between low birth weight and the later development of important cardiovascular risk factors in young African-Americans and white individuals. This relationship tends to be stronger in African-Americans than in whites, except for systolic blood pressure.

Birth weight is inversely associated with coronary heart disease in post-menopausal women: findings from the British women's heart and health study

OBJECTIVES

(1) To assess the association between birth weight and coronary heart disease (CHD) risk in a cohort of post-menopausal women, (2) to determine the combined effects of birth weight and adult body mass index on CHD, (3) to assess the role of insulin resistance as a mediating factor in the associations.

DESIGN

Cross sectional survey.

SETTING

23 British towns.

PARTICIPANTS

1394 women aged 60-79 years.

MAIN OUTCOME MEASURES

coronary heart disease (n = 199 cases).

RESULTS

Birth weight was inversely associated with CHD: age and survivor status of participant's mother adjusted odds ratio (95% confidence intervals) per 1 standard deviation (0.80 kg) increase in birth weight was 0.84 (0.72 to 0.97). This association strengthened to 0.80 (0.68 to 0.93) with further adjustment for adult body mass index, but there was no evidence of an interaction between birth weight and adult body mass index (p = 0.61). The association was not confounded by childhood or adulthood socioeconomic position or by adult smoking status of the participant. Adjustment for components of the insulin resistance syndrome attenuated the association to 0.87 (0.72 to 1.03).

CONCLUSIONS

Intrauterine exposures that affect fetal growth also affect future adult CHD risk. The inverse association between birth weight and CHD may in part be mediated via insulin resistance.

The developmental origins of the metabolic syndrome

Both epidemiological and clinical evidence suggest relationships between the antenatal environment and the risk of developing insulin resistance and associated cardiovascular disease (part of the metabolic syndrome) in middle age. However, interpretation of these findings has been controversial. Recent experimental observations provide considerable evidence for a causal model linking adaptive responses to early environmental cues and the later risk of disease. Evolutionary and life history theory provide possible explanations of why these phenomena have persisted and how they might cause disease. In this article, we review the clinical and experimental perspectives on the "developmental origins of disease" model in the context of these new concepts.

Peri-implantation undernutrition programs blunted angiotensin II evoked baroreflex responses in young adult sheep

An adverse environment around conception and implantation influences later fetal growth and development to term in humans and sheep. Indeed, preimplantation undernutrition of rats elevated the systolic blood pressure of the resultant adult offspring. In this study, adult cardiovascular function is examined in a slower growing, non-litter-bearing species after peri-implantation undernutrition. Eight ewes were fed to 50% equivalent food intake of 12 control ewes from 1 to 30 days (term approximately 147 days) only. Following consumption of an adequate diet to term, natural lambing, and then weaning, resting cardiovascular status and baroreflex function were examined in the resultant young adult offspring. Birth weight and postnatal growth to 1 year of age were unaffected by early undernutrition; however, nutrient-restricted sheep had increased pulse pressure, a reduced rate pressure product, and a leftward shift in their baroreflex function curve. Baroreflex sensitivity during angiotensin II infusion was also blunted in early nutrient-restricted sheep but the tachycardia following a reduction in central blood pressure appeared potentiated, relative to controls. The data suggest that peri-implantation undernutrition may program long-term cardiovascular dysfunction that ultimately increases the risk of hypertension later in life. An increase in regional angiotensin II activity during this critical early phase of development is a likely candidate mechanism for the effects observed. The data have broad implications for the health outcome of those offspring from mothers who were poorly nourished during early, often unknown pregnancy and for embryos artificially manipulated because of infertility treatment.

A life course approach to diet, nutrition and the prevention of chronic diseases

OBJECTIVE

To briefly review the current understanding of the aetiology and prevention of chronic diseases using a life course approach, demonstrating the life-long influences on the development of disease.

DESIGN

A computer search of the relevant literature was done using Medline-'life cycle' and 'nutrition' and reviewing the articles for relevance in addressing the above objective. Articles from references dated before 1990 were followed up separately. A subsequent search using Clio updated the search and extended it by using 'life cycle', 'nutrition' and 'noncommunicable disease' (NCD), and 'life course'. Several published and unpublished WHO reports were key in developing the background and arguments.

SETTING

International and national public health and nutrition policy development in light of the global epidemic in chronic diseases, and the continuing nutrition, demographic and epidemiological transitions happening in an increasingly globalized world. RESULTS OF REVIEW: There is a global epidemic of increasing obesity, diabetes and other chronic NCDs, especially in developing and transitional economies, and in the less affluent within these, and in the developed countries. At the same time, there has been an increase in communities and households that have coincident under- and over-nutrition.

CONCLUSIONS

The epidemic will continue to increase and is due to a lifetime of exposures and influences. Genetic predisposition plays an unspecified role, and with programming during fetal life for adult disease contributing to an unknown degree. A global rise in obesity levels is contributing to a particular epidemic of type 2 diabetes as well as other NCDs. Prevention will be the most cost-effective and feasible approach for many countries and should involve three mutually reinforcing strategies throughout life, starting in the antenatal period.

Inverse Association Between Birth Weight and C-Reactive Protein Concentrations in the MIDSPAN Family Study

Objective— Inflammation markers and low birth weight each predict elevated risk of cardiovascular events and type 2 diabetes. However, potential associations between the low-grade inflammatory response as represented by C-reactive protein (CRP) concentrations and low birth weight have been sparsely examined.

Methods and results— In the MIDSPAN Family Study, 1663 individuals had birth weight data and CRP concentrations measured as adults (age 30 to 59). The relationship between these parameters was examined after adjusting for factors known to influence CRP concentrations inclusive of age, body mass index, smoking, socio-economic deprivation, and hormone use in women. After adjusting for potential confounders, there was a negative association between birth weight and CRP, whereby a 1-kg increase in birth weight is associated with a 10.7% decrease in CRP (95% CI: 3.0% to 17.8% decrease). There was no strong evidence that the effects differed in men and women ( P =0.32).

Conclusion— Low birth weight contributes to elevated CRP concentration in adult life. Future studies are required to determine to what extent this association reflects catch-up centile crossing, in utero programming, or genetic factors.

Programming of adult cardiovascular function after early maternal undernutrition in sheep

The prenatal nutritional environment influences the subsequent risk of hypertension in adulthood. Animal studies have used, generally, the rat as a model species to illustrate the association between maternal nutrient intake and blood pressure in the resulting adult offspring. No study to date has shown programming of adult cardiovascular function in the sheep through maternal dietary intervention. We therefore fed pregnant sheep to either 100% recommended intake from day 0 of gestation to term [ approximately 147 days gestational age (dGA); controls n = 8] or to 50% recommended intake from day 0 to 95 dGA and thereafter to 100% intake (NR; n = 9). Sheep lambed naturally, offspring were weaned at 16 wk, and the male offspring were reared on pasture until 3 yr of age. At this time, cardiovascular catheters were inserted under halothane anesthesia and sheep were allowed 2-4 days recovery. Basal cardiovascular status and pressor responses to infusion of norepinephrine, angiotensin II, and captopril were then assessed alongside basal plasma concentrations of glucose, cortisol, and leptin. NR sheep were of similar birth weight to controls but at 3 yr of age had higher blood pressure before, but not after, feeding. Peripheral sensitivity to vasoconstrictor infusion was similar between dietary groups, although a reflex bradycardia was not apparent in NR sheep during norepinephrine infusion. Circulating leptin correlated well with fat mass and increased more after vasoconstrictor infusion in NR sheep. In conclusion, early NR has been shown to program aspects of cardiovascular control and adipocyte function in adult sheep.

Prenatal programming of angiotensin II type 2 receptor expression in the rat

Exposure to undernutrition during fetal life has been proposed as an underlying cause of adult hypertension. Epidemiological studies demonstrating relationships between low birth weight and later CVD are supported by animal experiments indicating that manipulations of the maternal diet in pregnancy exert programming effects upon blood pressure control. Pregnant female Wistar rats were fed a control diet (n 13) or a low-protein diet (n 12) throughout pregnancy. At delivery all animals were fed the same standard laboratory chow diet. Analysis of nephron number in kidneys obtained from 4-week-old offspring showed that this was significantly (P<0.05) reduced in animals exposed to maternal protein restriction. At this age rats exposed to low-protein diets in utero had systolic blood pressures that were significantly greater than those of control animals (+23 mmHg, P<0.05). Administration of ascending doses of angiotensin II (1-40 ng/kg body weight intravenously) to 10-week-old anaesthetised female rats showed that the pressor response to the peptide was greater and more prolonged in animals exposed to low-protein diets in utero. Renal expression of mRNA for the angiotensin II type 1A receptor was similar in the two groups of rats, but low-protein-exposed animals had significantly lower renal expression of the type 2 receptor (P=0.023). These results suggest that maternal nutritional status programmes expression of the renal angiotensin II type 2 receptor. This may play a key role in the impairment of renal development and the elevation of blood pressure noted in rats exposed to intra-uterine protein restriction.

Birth weight and cardiovascular risk factors in a cohort followed until 80 years of age: the study of men born in 1913

OBJECTIVES

To analyse whether there is a relation-ship between birth weight and cardiovascular risk factors given the influence of potential modifying factors from birth time, former generations and adult life.

DESIGN

Population-based cohort followed until 80 years of age.

SETTING

Sweden.

SUBJECTS

A total of 478 singleton men born in 1913 and participating in a population study in Gothenburg, Sweden, from age 50.

MAIN OUTCOME MEASURES

Systolic blood pressure (SBP), antihypertensive treatment, incident diabetes mellitus, and serum total cholesterol, serum triglycerides and waist circumference as both continuous variables and in the highest quintiles of their distributions.

RESULTS

After adjustment for the influence of birth time variables, hereditary factors and anthropometric and socio-economic adult life variables, SBP decreased by 3.7 mmHg per 1000 g increase of birth weight, the prevalence of antihypertensive treatment decreased by 32%, diabetes decreased by 53%, serum total cholesterol decreased by 0.20 mmol L(-1) and being in the top quintile of serum cholesterol decreased by 23%. The population risk percentage due to a birth weight < or =3000 g was for all three outcomes 3.8% and for antihypertensive treatment, diabetes and cholesterol 0.2, 18 and 2.5%, respectively.

CONCLUSIONS

Low birth weight thus seems to affect the development of increasing SBP, antihypertensive treatment, diabetes and high cholesterol even when potential effect modifiers from birth time, former generations and adult life were taken into account. In the general population, the risk percentage due to a birth weight < or =3000 g was largest for diabetes.

Indicators of Fetal Growth Do Not Independently Predict Blood Pressure in 8-Year-Old Australians

Inverse associations between size at birth and blood pressure (BP) in later life are commonly statistically significant only after adjustment for current size, consistent with change in size as the determinant. Few studies have been prospective or have included a range of potential confounders. Using regression models, including maternal and demographic variables, we examined associations between size at birth and BP in Australian children followed from week 16 of gestation to the age of 8 years. BP measurements were available from 1417 children born after 37 weeks gestation without congenital abnormalities. In models adjusted only for sex, the birthweight (BW), birth length, ponderal index, head circumference, chest circumference, abdominal girth, mid-arm circumference, triceps skinfold, placental weight, or BW/placental weight ratio did not significantly predict SBP in 8-year-olds. With adjustment for current size, associations were inverse but not statistically significant (regression coefficients: BW, −1.11; 95% confidence limits [CL], −2.22, 0.01; birth length, −0.25; 95% CL, −0.52, 0.24) and remained nonsignificant after adjustment for confounders. Current weight, height, or body mass index significantly predicted SBP and DBP ( P <0.001) with differences of 8/4 mm Hg between upper and lower quartiles; effects were similar in infants with lower and higher BW. These findings are consistent with postnatal change in size as the major determinant of BP in 8-year-olds and are important in the context of the worldwide “epidemic” of obesity in childhood as a likely precursor of increasing rates of hypertension in adults.

Effect of Birth Weight on Blood Pressure and Body Size in Early Adolescence

The fetal programming theory that birth weight contributes to blood pressure or body size in later life is examined in this study. A prospective longitudinal study was conducted on subjects who were examined as newborns and prospectively interviewed and re-examined at 11 to 14 years old. Low birth weight (<2500 g) was present in 36% of the sample. The adolescent examination included measurements of blood pressure (BP), both auscultation and oscillometric methods; anthropometrics (height, weight, and body mass index [BMI]); health status; and health behaviors. Data were analyzed on 250 subjects. Correlation coefficients of birth weight with all BP measures were nonsignificant, except for the last auscultated diastolic BP ( r =0.19, P <0.01), which had a positive relationship. The simple correlation coefficients of birth weight with adolescent body size were significant and positive for weight and BMI. After multiple linear regression analyses with adjustments for age, Tanner stage, and gestational age, there was no significant effect of birth weight on adolescent weight or BMI. No significant correlations were detected for ponderal index at birth with adolescent measures. This study, which includes a substantial portion of low-birth-weight cases (36%), indicates that birth weight does not correlate negatively with later BP. These results do not support the low-birth-weight theory and indicate that childhood factors that are more proximal have a greater effect on adolescent BP than intrauterine factors.

Birth weight and lipids in a national birth cohort study

OBJECTIVE

To investigate the association between birth weight and lipid levels in a 53-year-old birth cohort from England, Scotland, and Wales.

METHODS AND RESULTS

Lipid levels were obtained from nonfasting blood samples, collected at the most recent follow-up of the MRC National Survey of Health and Development, for 2559 men and women. Regression models indicated that in men, a 1-kg increase in birth weight was associated with a 0.13-mmol/L decrease (95% CI: -0.23, -0.01) in total cholesterol at age 53 years (P=0.03), compared with a 0.02-mmol/L (95% CI: -0.11, 0.15) increase in women and a 0.06-mmol/L (95% CI: -0.15, 0.02) decrease in men and women combined. Adjustment for current height and body mass index (BMI) in men reduced the size of the relationship, with height being responsible for the reduction. Adult height and height at 2 and 4 years were significantly associated with total cholesterol in men and in men and women combined. The negative association between total cholesterol and birth weight was strongest among men with high BMI at age 53 years (P=0.03 for test for interaction between birth weight and BMI). There was no significant association between birth weight and LDL or HDL cholesterol in men or women before adjustment, but there was a positive association with HDL in women. When both sexes were analyzed together, an association was seen after adjustment for current body size. No confounding of these findings with social class was observed in this study.

CONCLUSIONS

Our results suggest that the small effect of birth weight on lipid levels at age 53 years has a limited public health impact. The findings suggest that childhood height growth may be more important than prenatal growth.

Modeling postnatal exposures and their interactions with birth size

The fetal origins of adult disease hypothesis postulates that the inverse association between birth weight and later adverse outcome reflects fetal programming that increases the risk of later disease. However, low birth weight is associated with catch-up after birth, and weight gain is itself a risk factor for later disease. It is difficult to disentangle the effects on outcome of the size and growth components of weight change through time. This paper presents the life course plot, a device to display both size and growth effects simultaneously. It is based on the multiple-regression analysis of the outcome on the various weights, expressed as z-scores, and the plot displays the coefficients plotted against the corresponding ages of measurement. Examples from Brazil (Pelotas) and the Phillippines (Cebu) relate blood pressure in adolescence to weight through childhood. They show small inverse weight effects in infancy, but early weight is less important than weight and weight gain during adolescence. In addition, birth length in the Cebu study affects the strength of the relationship between weight and blood pressure in adolescence. This suggests a fetal programming effect, with children who were relatively long at birth having a more sensitive relationship between blood pressure and weight at age 15. Whether this is a good or a bad thing is not immediately clear.

Stroke

Stroke is a major public-health burden worldwide. Prevention programmes are essential to reduce the incidence of stroke and to prevent the all but inevitable stroke epidemic, which will hit less developed countries particularly hard as their populations age and adopt lifestyles of the more developed countries. Efficient, effective, and rapid diagnosis of stroke and transient ischaemic attack is crucial. The diagnosis of the exact type and cause of stroke, which requires brain imaging as well as traditional clinical skills, is also important when it will influence management. The treatment of acute stroke, the prevention and management of the many complications of stroke, and the prevention of recurrent stroke and other serious vascular events are all improving rapidly. However, stroke management will only be most effective when delivered in the context of an organised, expert, educated, and enthusiastic stroke service that can react quickly to the needs of patients at all stages from onset to recovery.

Birthweight, childhood social class, and change in adult blood pressure in the 1946 British birth cohort

BACKGROUND

The negative effect of birthweight on systolic blood pressure has been suggested to be initiated in utero and amplified with age. We aimed to investigate this hypothesis.

METHODS

A sample of 3634 people from a birth cohort study of men and women born in Britain in 1946 were included in analyses. Cohort members have been contacted regularly since birth, and systolic and diastolic blood pressures were measured at ages 36, 43, and 53 years. Multilevel models, with blood pressure as a repeated outcome, were used to test the amplification hypothesis and to compare results for birthweight with those for childhood social class.

FINDINGS

Considering both men and women together, a consistent negative association between birthweight and systolic blood pressure was noted from age 36 to 53 years, but no evidence was recorded of substantial amplification with age. A 1 kg higher birthweight was associated with a slower mean increase in systolic blood pressure by -0.4 mm Hg (95% CI -1.3 to 0.4; p=0.3) per 10-year increase in age. Birthweight was not associated with diastolic blood pressure at any age. People from a manual social class in childhood had higher systolic and diastolic blood pressure than did those from a non-manual class. The effect on systolic blood pressure rose with age, by 1.0 mm Hg (95% CI 0.1 to 2.0; p=0.03) per 10 years, but was largely accounted for by current body-mass index, which was an increasingly strong determinant of blood pressure.

INTERPRETATION

These findings suggest that weight control throughout life is key to prevention of raised blood pressure during middle age. Understanding the link between the early childhood socioeconomic environment and adult obesity could make this strategy more effective.

Relationship between birthweight and blood lipid concentrations in later life: evidence from the existing literature

BACKGROUND

It has been suggested that there is a link between fetal growth and chronic diseases later in life. Several studies have shown a negative association between birthweight and cardiovascular diseases, as well as cardiovascular disease risk factors, such as blood pressure and type 2 diabetes. Far fewer studies have focused on the association between size at birth and blood lipid concentrations. We have conducted a qualitative assessment of the direction and consistency of the relationship between size at birth and blood lipid concentrations to see whether the suggested relationship between intrauterine growth and cardiovascular diseases is mediated by lipid metabolism.

METHODS

A literature search covering the period January 1966 to January 2003 was performed using Medline, Embase, and Web of Science. All papers written in English and reporting the relationship between size at birth and lipid levels in humans were assessed. Bibliographies were searched for further publications.

RESULTS

From an initial screen of 1198 references, 39 papers were included involving 28 578 individuals. There was no consistent relationship between size at birth and blood lipid levels; the one exception being triglyceride concentration, which showed statistically significant negative or U-shaped, but not positive, relationships with birthweight.

CONCLUSION

This review does not strongly support a link between birthweight and blood lipid levels in later life. However, the research in this area is limited and in order to make any definitive conclusions, longitudinal studies with sufficient power, data, and prospective follow-up are needed.

Twinning

Twinning has fascinated human beings over the centuries. New technologies and large study groups have led to improved documentation of frequency and complications in twin pregnancies and long-term outcomes. Artificial reproductive technologies have led to a pronounced rise in numbers of dizygotic and monozygotic twins. Although spontaneous dizygotic twinning is clearly associated with increased concentration of follicle-stimulating hormone and ovulation of more than one egg, causes of monozygotic twinning remain illusive. Twin studies are used increasingly to study complex traits and disorders: however, caution is suggested, since twins might not be representative of a typical singleton pregnancy. Monozygotic twinning seems to represent an anomaly in itself, with an increased number of spontaneous abortions and structural congenital anomalies. Both monozygotic and dizygotic twins have growth rates that slow at 30 weeks in utero and might be programmed both developmentally and biochemically earlier in pregnancy to have different responses at birth and after birth compared with singletons.

Low birth weight is associated with increased sympathetic activity: dependence on genetic factors

BACKGROUND

Low birth weight may be associated with high blood pressure in later life through genetic factors, an association that may be explained by alterations in sympathetic and parasympathetic activity. We examined the association of birth weight with cardiac pre-ejection period and respiratory sinus arrhythmia (indicators of cardiac sympathetic and parasympathetic activity, respectively) and with blood pressure in 53 dizygotic and 61 monozygotic adolescent twin pairs.

METHODS AND RESULTS

Birth weight of the twins was obtained from the mothers. Pre-ejection period and respiratory sinus arrhythmia were measured with electrocardiography and impedance cardiography at rest, during a reaction time task, and during a mental arithmetic task. In the overall sample, lower birth weight was significantly associated with shorter pre-ejection period at rest, during the reaction time task, and during the mental arithmetic task (P=0.0001, P<0.0001, and P=0.0001, respectively) and with larger pre-ejection period reactivity to the stress tasks (P=0.02 and P=0.06, respectively). In within-pair analyses, differences in birth weight were associated with differences in pre-ejection period at rest and during both stress tasks in dizygotic twin pairs (P=0.01, P=0.06, and P=0.2, respectively) but not in monozygotic twin pairs (P=0.9, P=1.0, and P=0.5, respectively). Shorter pre-ejection period explained approximately 63% to 84% of the birth weight and blood pressure relation.

CONCLUSIONS

Low birth weight is associated with increased sympathetic activity, and this explains a large part of the association between birth weight and blood pressure. In addition, our findings suggest that the association between birth weight and sympathetic activity depends on genetic factors.

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

OBJECTIVE

To examine the relationship between birth weight and blood total cholesterol (TC) and to compare its strength with that of the relationship between current body mass index and TC.

METHODS

1). Cross-sectional study of adolescents, with retrospective ascertainment of birth weight from birth records or parental recall; 2). systematic review of studies examining the relations between birth weight and cholesterol at all ages.

PARTICIPANTS

1). 1532 individuals (92% white, 55% male) in 10 British towns; 2). 28 studies with 32 observations showing the change in TC per 1 kg increase in birth weight-6 in infancy, 14 in adolescents, 12 in adults.

RESULTS

In the cross-sectional study, there was a weak inverse relation between birth weight and TC level (-.061 mmol/L fall in TC per kg increase in birth weight, 95% confidence interval -.131 to.008 mmol/L per kg) which was little affected by adjustment for current body size. The difference in TC corresponding to an interquartile range increase in birth weight (-.03 mmol/L) was approximately a quarter of that for an equivalent increase in body mass index (.11 mmol/L). In the systematic review, an inverse association between birth weight and TC of a similar size to that in the cross-sectional study was observed (-.048 mmol/L per kg, 95% confidence interval -.078 to -.018 mmol/L per kg) similar in strength at all ages.

CONCLUSION

The relation of fetal nutrition to TC appears to be weak and is probably of limited public health importance when compared with the effects of childhood obesity.

Contribution of contemporaneous risk factors to social inequality in coronary heart disease and all causes mortality

BACKGROUND

The relationship between low social status and premature mortality is well established, although the explanation for this link is unclear. This study explores the contribution to the social inequalities in coronary heart disease (CHD) and death of smoking status, cotinine, alcohol status, type A personality score, leisure activity, diabetes, systolic and diastolic blood pressure, body mass index, total and HDL cholesterol, triglycerides, fibrinogen, and vitamin C consumption.

METHODS

A random sample of 11,629 Scottish men and women, ages 40-59 years, was recruited in 1984-1987 and followed up for an average of 7.7 years for death and major coronary events. Social status was measured by housing tenure--renters being more socially deprived. Hazard ratios were computed from Cox models.

RESULTS

Adjusted for age, renters have 1.48 times the risk of CHD compared to owner-occupants (95% CI: 1.21, 1.80) in men and 2.64 (1.89, 3.68) in women, and for all-cause mortality 1.55 (1.26, 1.90) and 2.12 (1.58, 2.84). The 14 risk factors explained 73% (men) and 77% (women) of the social differences in CHD. Equivalent figures for deaths were 51 and 64%.

CONCLUSIONS

Fourteen contemporaneous risk factors, smoking being the most important, explain most of the social differential in CHD and death.

The thrifty phenotype hypothesis: thrifty offspring or thrifty mother?

Medical research is increasingly focusing on the contribution of nutritional programming to disease in later life. Programming is a process whereby a stimulus during a critical window of time permanently affects subsequent structure, function or developmental schedule of the organism. The thrifty phenotype hypothesis is widely used to interpret such studies, with early growth restriction seen as adaptation to environmental deprivation. However, such permanent adjustment is less beneficial than maintaining flexibility so as to recover from early growth deficits if the environment improves. Thus, the existing thrifty phenotype hypothesis fails to explain why plasticity is lost so early in development in species with extended growth. One explanation is that the developing organism simply cannot maintain phenotypic plasticity throughout the period of organ growth. This article adds a life history perspective, arguing that programming of the offspring may in some species benefit maternal fitness more than it does that of individual offspring. Closing the critical window early in development allows the preservation of maternal strategy in offspring phenotype, which in humans benefits the mother by constraining offspring demand after weaning. The offspring gains by being buffered against environmental fluctuations during the most sensitive period of development, allowing coherent adaptation of organ growth to the state of the environment. The critical window is predicted to close when offspring physiology becomes independent of maternal physiology, the timing of which depends on offspring trait. Because placental nutrition and lactation buffer against short-term environmental fluctuations, maternal strategy is predicted to derive from long-term experience, encapsulated in maternal size and nutritional status. Such an approach implies that public health programmes for improving birth weight may be more effective if they target maternal development rather than nutrition during pregnancy. Equally, aggressive nutritional management of infants born small or pre-term may induce the very environmental fluctuations that are naturally softened by maternal nutrition.

Life course influences on insulin resistance: findings from the British Women's Heart and Health Study

OBJECTIVE

To assess the independent associations of a broad range of early life risk factors and adult obesity with adult insulin resistance.

RESEARCH DESIGN AND METHODS

This was a cross-sectional study of 1,394 women, aged 60-79 years, from 23 British towns.

RESULTS

There was a strong (independent of confounding factors, other early life factors, and adult waist-to-hip ratio) inverse association between birth weight and insulin resistance in women in the highest third of BMI (>28.77 kg/m2): -0.12 (95% CI -0.19 to -0.04) log homeostasis model assessment (HOMA) score per 1 SD birth weight, but no association between birth weight and insulin resistance in women in the two lowest thirds of BMI (P for interaction = 0.04). Offspring birth weight, own leg length, and childhood manual social class did not interact with adult obesity and were all independently inversely associated with insulin resistance: -0.05 (-0.09 to -0.01) log HOMA score per 1 SD offspring birth weight, -0.09 (-0.12 to -0.06) log HOMA score per 1 SD leg length, and a -0.07 (-0.14 to 0.00) difference in log HOMA score between manual and nonmanual childhood social class. Childhood manual social class and shorter leg length were both independently associated with adverse lipid profiles. BMI and waist-to-hip ratio were independently positively associated with insulin resistance and with all other components of the insulin resistance syndrome.

CONCLUSIONS

Insulin resistance is an important risk factor for type 2 diabetes and coronary heart disease. Our results suggest that genetic factors, intrauterine environment, early childhood, and adult environmental factors are all relevant in determining adult insulin resistance.