Adult blood pressure and climate conditions in infancy: a test of the hypothesis that dehydration in infancy is associated with higher adult blood pressure

Short-term acute constipation and not short-term acute diarrhea altered cardiovascular variables in male Wistar rats

Gastrointestinal dysmotility is a substantial public health challenge globally. Based on previous findings in developed countries, it has been observed that there is an association between diarrhea, constipation, and some cardiovascular variables. This study investigated the effects of experimentally-induced short-term acute constipation and short-term acute diarrhea on certain cardiovascular variables in rats. Thirty (30) male Wistar rats (150 -180 g) were divided into three groups; Control, Diarrhoea, and Constipation. The experiment was carried out in 2 phases, the period after induction and the recovery period, and 5 animals per group were used for each phase. The control group received an equivalent amount of distilled water while Diarrhoea and the Constipation group were induced by oral administration of 2ml Castor oil and administration of Loperamide (3mg/kg, b.d, orally x 3 days), respectively. Cardiovascular variables were assessed using the Edan Scientific® Electrocardiography and  Heart Rate Variability machine. Recovery was allowed for 4 days after the onset of the procedure and cardiovascular parameters were reassessed. Post-induction Systolic Blood Pressure (SBP), Diastolic Blood Pressure (DBP), Mean Arterial Pressure (MAP) and Heart Rate (HR) significantly increased in constipated rats (153.2 ± 2.9 mmHg; 109.0 ± 3.7 mmHg;     123.7 ± 3.2 mmHg; 123.4±5.6 bpm) when compared with the control values (95.5±4.8 mmHg; 61.2 ± 3.5 mmHg; 72.6 ± 3.6 mmHg; 72.3 ± 5.2 bpm), respectively. The recovery SBP, DBP, MAP, and Heart Rate in the constipated group remained significantly higher compared to the control. Diarrhea had no significant effect on the parameters determined in both post-induction and recovery phases. The electrical activities did not change in both experimental groups compared to the control. This study revealed increased SBP, DBP, MAP, and HR in short-term acute constipated rats but not so with short-term acute experimental diarrhea.

Childhood socio-economic conditions and risk of cardiovascular disease: results from a pooled sample of 14 011 adults from India

Background

South Asians are at an increased risk of premature cardiovascular disease, but the reasons for this are unclear. Poor socio-economic conditions in childhood are associated with an increased risk of cardiovascular disease in many high-income countries and may be particularly relevant to South Asia, where socio-economic deprivation is more prevalent and severe. However, evidence from South Asia is limited.

Methods

We pooled data from two large population-based studies in India to provide a geographically representative and adequately powered sample of Indian adults. We used multilevel linear regression models to assess associations between standard of living index (SLI) in childhood (measured by recalled household assets at age 10–12 years) and major cardiovascular risk factors including adiposity, blood pressure, and fasting blood lipids, glucose and insulin.

Results

Data on 14 011 adults (median age 39 years, 56% men) were analysed. SLI in childhood was inversely associated with systolic and diastolic blood pressure, independent of socio-economic conditions in adulthood, with beta coefficients (95% CIs) of −0.70 mmHg (−1.17 to −0.23) and −0.56 mmHg (−0.91 to −0.22), respectively, per SD increase in SLI in childhood. There was no strong evidence for an association between SLI in childhood and other risk factors of cardiovascular disease.

Conclusions

Poor socio-economic conditions in childhood may contribute to the increased risk of premature cardiovascular disease among South Asians by raising their blood pressure. Elucidating the mechanisms and improving socio-economic conditions for children in South Asia could provide major reductions in the burden of cardiovascular disease.

Quasi-experimental study designs series-paper 6: risk of bias assessment

OBJECTIVES

Rigorous and transparent bias assessment is a core component of high-quality systematic reviews. We assess modifications to existing risk of bias approaches to incorporate rigorous quasi-experimental approaches with selection on unobservables. These are nonrandomized studies using design-based approaches to control for unobservable sources of confounding such as difference studies, instrumental variables, interrupted time series, natural experiments, and regression-discontinuity designs.

STUDY DESIGN AND SETTING

We review existing risk of bias tools. Drawing on these tools, we present domains of bias and suggest directions for evaluation questions.

RESULTS

The review suggests that existing risk of bias tools provide, to different degrees, incomplete transparent criteria to assess the validity of these designs. The paper then presents an approach to evaluating the internal validity of quasi-experiments with selection on unobservables.

CONCLUSION

We conclude that tools for nonrandomized studies of interventions need to be further developed to incorporate evaluation questions for quasi-experiments with selection on unobservables.

Approaches for drawing causal inferences from epidemiological birth cohorts: a review

Large-scale population-based birth cohorts, which recruit women during pregnancy or at birth and follow up their offspring through infancy and into childhood and adolescence, provide the opportunity to monitor and model early life exposures in relation to developmental characteristics and later life outcomes. However, due to confounding and other limitations, identification of causal risk factors has proved challenging and published findings are often not reproducible. A suite of methods has been developed in recent years to minimise problems afflicting observational epidemiology, to strengthen causal inference and to provide greater insights into modifiable intra-uterine and early life risk factors. The aim of this review is to describe these causal inference methods and to suggest how they may be applied in the context of birth cohorts and extended along with the development of birth cohort consortia and expansion of "omic" technologies.

The time of our lives: recognizing the contributions of Mannheim, Neugarten, and Riley to the study of aging

Time is central to the study of aging, but multiple dimensions of time, especially its subjective sense, merit more systematic attention in gerontology. This essay honors the intellectual legacy of Karl Mannheim, Bernice Neugarten, Matilda Riley, and others for drawing attention to the social dimensions of time relevant for the scientific study of aging. I summarize major contributions of these social scientists for the study of aging and note points of overlap and distinction. Although their writings have led gerontologists to think more systematically about life course timing and trajectories, there is relatively little empirical research on temporal perceptions in such trajectories and the interplay of objective and subjective elements of time.

Associations between household and neighbourhood socioeconomic status and systolic blood pressure among urban South African adolescents

Factors resulting in high risk for cardiovascular disease have been well studied in high income countries, but have been less well researched in low/middle income countries. This is despite robust theoretical evidence of environmental transitions in such countries which could result in biological adaptations that lead to increased hypertension and cardiovascular disease risk. Data from the South African Birth to Twenty cohort, Bone Health sub-sample (n = 358, 47% female), were used to model associations between household socioeconomic status (SES) in infancy, household/neighbourhood SES at age 16 years, and systolic blood pressure (multivariate linear regression) and risk for systolic pre-hypertension (binary logistic regression). Bivariate analyses revealed household/neighbourhood SES measures that were significantly associated with increased systolic blood pressure. These significant associations included improved household sanitation in infancy/16 years, caregiver owning the house in infancy and being in a higher tertile (higher SES) of indices measuring school problems/environment or neighbourhood services/problems/crime at 16 years of age. Multivariate analyses adjusted for sex, maternal age, birth weight, parity, smoking, term birth, height/body mass index at 16 years. In adjusted analyses, only one SES variable remained significant for females: those in the middle tertile of the crime prevention index had higher systolic blood pressure (β = 3.52, SE = 1.61) compared with the highest tertile (i.e. those with the highest crime prevention). In adjusted analyses, no SES variables were significantly associated with the systolic blood pressure of boys, or with the risk of systolic pre-hypertension in either sex. The lack of association between SES and systolic blood pressure/systolic pre-hypertension at age 16 years is consistent with other studies showing an equalization of adolescent health inequalities. Further testing of the association between SES and systolic blood pressure would be recommended in adulthood to see whether the lack of association persists.

Season of birth and exceptional longevity: comparative study of american centenarians, their siblings, and spouses

This study explores the effects of month of birth (a proxy for early-life environmental influences) on the chances of survival to age 100. Months of birth for 1,574 validated centenarians born in the United States in 1880-1895 were compared to the same information obtained for centenarians' 10,885 shorter-lived siblings and 1,083 spouses. Comparison was conducted using a within-family analysis by the method of conditional logistic regression, which allows researchers to control for unobserved shared childhood or adulthood environment and common genetic background. It was found that months of birth have significant long-lasting effect on survival to age 100: siblings born in September-November have higher odds to become centenarians compared to siblings born in March. A similar month-of-birth pattern was found for centenarian spouses. These results support the idea of early-life programming of human aging and longevity.

A new approach to age-period-cohort analysis using partial least squares regression: the trend in blood pressure in the Glasgow Alumni cohort

Due to a problem of identification, how to estimate the distinct effects of age, time period and cohort has been a controversial issue in the analysis of trends in health outcomes in epidemiology. In this study, we propose a novel approach, partial least squares (PLS) analysis, to separate the effects of age, period, and cohort. Our example for illustration is taken from the Glasgow Alumni cohort. A total of 15,322 students (11,755 men and 3,567 women) received medical screening at the Glasgow University between 1948 and 1968. The aim is to investigate the secular trends in blood pressure over 1925 and 1950 while taking into account the year of examination and age at examination. We excluded students born before 1925 or aged over 25 years at examination and those with missing values in confounders from the analyses, resulting in 12,546 and 12,516 students for analysis of systolic and diastolic blood pressure, respectively. PLS analysis shows that both systolic and diastolic blood pressure increased with students' age, and students born later had on average lower blood pressure (SBP: -0.17 mmHg/per year [95% confidence intervals: -0.19 to -0.15] for men and -0.25 [-0.28 to -0.22] for women; DBP: -0.14 [-0.15 to -0.13] for men; -0.09 [-0.11 to -0.07] for women). PLS also shows a decreasing trend in blood pressure over the examination period. As identification is not a problem for PLS, it provides a flexible modelling strategy for age-period-cohort analysis. More emphasis is then required to clarify the substantive and conceptual issues surrounding the definitions and interpretations of age, period and cohort effects.

Effect of seasonal programming on fetal development and longevity: links with environmental temperature

This study examined the effect of birth season on fetal development and longevity using two independent databases of all Greek citizens that were born (total: 516,874) or died (total: 554,101) between 1999 and 2003. We found significantly increased birth weight, gestational age, and longevity in individuals born during the autumn and winter seasons of the year. These individuals also demonstrated statistically significantly lower prevalence rates for fetal growth restriction and premature birth. Furthermore, we found that increased temperature at birth was associated with adverse effects on fetal development and longevity. In conclusion, our results show strong effects of season of birth on fetal development and longevity mediated, at least in part, by environmental temperature at time of birth.

Lactase persistence-related genetic variant: population substructure and health outcomes

Lactase persistence is an autosomal-dominant trait that is common in European-derived populations. A basic tendency for lactase persistence to increase from the southeast to the northwest across European populations has been noted, but such trends within countries have not been extensively studied. We genotyped the C/T(-13910) variant (rs4988235) that constitutes the putatively causal allele for lactase persistence (T allele representing persistence) in a general population sample of 3344 women aged 60-79 years from 23 towns across Britain. We found an overall frequency of 0.253 for the C (lactase non-persistence) allele, but with considerable gradients of decreasing frequency from the south to the north and from the east to the west of Britain for this allele. Daily sunlight was positively related to C (non-persistence) allele prevalence. However, sunlight exposure and latitude are strongly correlated, and it was not possible to identify which is the primary factor statistically underlying the distribution of lactase persistence. The C/T(-13910) variant (rs4988235) was not related to drinking milk or bone health (although drinking milk itself was protective of bone health), and was essentially unrelated to a wide range of other lifestyle, health and demographic characteristics. One exception was general health being rated as being poor or fair, for which there was an odds ratio of 1.38 (1.04, 1.84) for women homozygous for the C allele; on adjustment for latitude and longitude of place of birth, this attenuated to 1.19 (0.87, 1.64). The lactase persistence variant could contribute to the examination of data for the existence of, and then statistical control for, population substructure in genetic association studies.

Frequency of diarrhoea as a predictor of elevated blood pressure in children

BACKGROUND

Diarrhoeal illness is a major public health problem for children worldwide, particularly among developing countries, and is a proxy condition for severe dehydration. It has been hypothesized that severe dehydration in the first 6 months of life could be associated with increased blood pressure later in life. This study aimed to explore whether frequency of diarrhoea is associated with elevated blood pressure in children in a setting with a high incidence of diarrhoeal disease.

METHODS

The present study is a cross-sectional study of blood pressure among children from a longitudinal child diarrhoeal disease cohort in Lima, Peru. From 2001 to 2006, daily diarrhoeal surveillance was made. Children were revisited in 2006 and blood pressure was measured. Diarrhoeal exposures were evaluated in terms of total number of diarrhoea days, number of episodes of diarrhoea, persistent diarrhoeal episodes and by the quartiles of daily incidence and episode incidence of diarrhoea.

RESULTS

The overall incidence of diarrhoeal episodes at age under 1 year was 4.35 (95% confidence interval: 3.79-4.98) and under 5 years was 2.80 (95% confidence interval: 2.69-2.92). No association was observed between the total number of diarrhoeal days, diarrhoeal episodes or diarrhoeal incidence rates with childhood blood pressure. There was weak evidence that hospital admission due to severe dehydration in the first year of life showed a gradient towards an increase in both, systolic and diastolic blood pressure.

CONCLUSION

In the first study to date to examine the association in a setting with a high incidence of diarrhoeal disease, diarrhoeal frequency did not show an association with increased blood pressure. Our observations of elevated levels of blood pressure among those admitted into hospitals in the first year of life are in line with the original hypothesis of dehydration in early infancy and high blood pressure. However, the effect of episodes of severe dehydration on later blood pressure remains uncertain.

Challenges and novel approaches in the epidemiological study of early life influences on later disease

The influence of factors acting during early life on health outcomes of offspring is of considerable research and public health interest. There are, however, methodological challenges in establishing robust causal links, since exposures often act many decades before outcomes of interest, and may also be strongly related to other factors, generating considerable degrees of potential confounding. With respect to pre-natal factors, the degree of confounding can sometimes be estimated by comparing the association between exposures experienced by the mother during pregnancy and outcomes among the offspring with the association of the same exposures experienced by the father during the pregnancy period and offspring outcomes. If the effects are due to an intra-uterine exposure, then maternal exposure during pregnancy should have a clearly greater influence than paternal exposure. If confounding by socio-economic, behavioural or genetic factors generates the association then maternal and paternal pregnancy exposures will be related in the same way with the outcome. For early life exposures it is also possible to compare outcomes in siblings who are concordant or discordant for the exposure, which will reduce the influence of family-level confounding factors. A different approach is that of Mendelian randomization, which utilises genetic variants of known effect that can proxy for modifiable exposures and are also not in general related to potential confounding factors, or influenced by disease. In other settings the use of non-genetic instrumental variables is possible. A series of examples of the application of these approaches are presented and their potentials and limitations discussed. Other epidemiological strategies are briefly reviewed. It is concluded that the naïve acceptance of findings utilising conventional epidemiological methods in this setting is misplaced.

Cash component of conditional cash transfer program is associated with higher body mass index and blood pressure in adults

The cash component of Oportunidades, a large conditional cash transfer (CCT) program in Mexico, has previously been shown to be associated with better outcomes for child growth and development. The objective of this analysis was to determine whether the cash transfers were also associated with positive outcomes for adult health. Oportunidades was originally randomized across 506 rural (<2500 inhabitants) communities assigned to immediate incorporation into the program in 1997 or incorporation 18 mo later. Adults (n = 1649 early, n = 2039 late intervention) aged 18-65 y were then assessed in 2003. All of the households included in the analysis reported here complied with Oportunidades's requirements for the entire period, but some received higher cumulative cash transfers because they were living in communities randomized to begin receiving transfers earlier and/or they accumulated cash at a faster rate because they had more school-aged children at baseline. Our primary findings were that a doubling of cumulative cash transfers to the household was associated with higher BMI (beta = +0.83, 95% CI 0.46, 1.20; P < 0.0001), higher diastolic blood pressure (beta = +1.19, 95% CI 0.09, 2.29; P = 0.03), and higher prevalence of overweight [odds ratio (OR) = 1.41, 95% CI 1.18, 1.67; P < 0.0001), grade I obesity (OR = 1.41, 95% CI 1.14, 1.75; P = 0.002), and grade II obesity (OR = 1.57, 95% CI 1.05, 2.36; P = 0.03), while controlling for a wide range of covariates, including household composition at baseline. Oportunidades has been portrayed as a model for CCT programs worldwide, but the results reported here support the notion that the cash component of Oportunidades may be negatively associated with some adult health outcomes.

Early life diarrhoea and later blood pressure in a developing country: the 1982 Pelotas (Brazil) birth cohort study

BACKGROUND

It has recently been hypothesised that acute dehydration in early childhood may "programme" increased blood pressure via salt retention. We examined whether there was an association between episodes of diarrhoea (a proxy for acute dehydration) and later measured blood pressure.

METHODS

In the 1982 Pelotas birth cohort study (Brazil), parents/carers reported hospital admissions for diarrhoea in the first 12 and 20 months of study members' lives. Blood pressure was subsequently measured directly in adolescence (aged 15, 18, 19 years) and early adulthood (aged 23 years).

RESULTS

We found no evidence of an association between diarrhoea in the first 12 months of life and blood pressure measured at any point in adolescence or early adulthood. These findings were unchanged after adjustment for a range of covariates. Equally null results were apparent when diarrhoea admissions in the first 20 months of life, access to home sanitation and use of piped water were the exposures of interest.

CONCLUSIONS

Early life proxies for dehydration and diarrhoea were unrelated to later blood pressure in this examination, the most comprehensive to date, of the potential association.

Diarrhoea in childhood and cause-specific mortality in older age: analyses of 5642 deaths in 33,261 individuals from the Hertfordshire studies

The objective of these analyses were to examine if episodes of diarrhoea in childhood are related to adult coronary heart disease (CHD) mortality. Data were pooled from two prospective UK cohort studies (participants born 1923--1939). Reported diarrhoea in infancy (3.1%) and between 1 and 5 years (1.1%) was rare. No relationship between diarrhoea in infancy and CHD mortality or mortality from all-causes and cardiovascular disease was observed. Although diarrhoea between 1 and 5 years was also not related to CHD risk, slightly lower rates of total and cardiovascular disease mortality were apparent in this group relative to the diarrhoea-free. In the largest study to date to examine the relation, there was no evidence that diarrhoea in early life had an influence on later CHD mortality.

Examining life-course influences on chronic disease: the Ribeirão Preto and São Luís birth cohort studies (Brazil)

More than any other low- and middle-income country, Brazil has the longest research tradition of establishing, maintaining and exploiting birth cohort studies. This research pedigree is highlighted in the present issue of the Brazilian Journal of Medical and Biological Research, which contains a series of twelve papers from the Ribeirão Preto and São Luis birth cohort studies from the Southeast and Northeast of Brazil, respectively. The topics covered in this raft of reports vary and include predictors of perinatal health and maternal risk factors, early life determinants of cardiovascular risk factors in childhood and adolescence, use of health services, and a description of dietary characteristics of young adults, amongst other topics. There is also a guide to the background, objectives, sampling and protocols employed across these studies, which, together with similar pieces published in past issues of the Brazilian Journal, serve as a very useful starting point, particularly for potential collaborators. In the fervent hope that further follow-up of these cohorts will take place--we provide our own justification for cohort maintenance and extension in this issue--future data collection could include: genetic material, atherosclerosis, ascertained, for instance, by intima-media thickness, and IQ testing in children--scores from which are emerging as potentially important predictors of adult health outcomes up to six decades later.

Childhood and adulthood socioeconomic position across 20 causes of death: a prospective cohort study of 800,000 Norwegian men and women

OBJECTIVE

To assess the impact of childhood and adulthood socioeconomic position (SEP) across 20 causes of death in a large population-wide sample of Norwegian men and women.

METHODS

Census data on parental occupational class from 1960 and data from the tax register on household income in 1990 were linked to the death register for 1990-2001, and 20 causes of death were studied. Relative indices of inequalities were computed. Norwegians in the age group 0-20 years in 1960 and still alive in 1990 were followed for deaths in 1990 to 2001. This follow up involved 795,324 individuals (78%) and 20,887 deaths.

MAIN RESULTS

In men most support for an effect of childhood socioeconomic position was found for stomach cancer, lung cancer, coronary heart disease, "other violent death", and all causes of death. In women similar effects were found for lung cancer, cervical cancer, coronary heart disease, chronic obstructive pulmonary disease, and all causes of death.

CONCLUSIONS

The effect of childhood socioeconomic position relative to adulthood varies by cause of death. Although there are some exceptions, the patterns in men and women are generally similar.

Measuring dietary sodium intake in infancy: a review of available methods

It has been hypothesised that infancy may be a particularly sensitive period with respect to the effect of dietary sodium (salt) intake on later blood pressure. If this is the case, interventions to reduce dietary sodium intake in infancy could have major public health impact by reducing cardiovascular disease in the future. However, research in this area is hampered by difficulties of how to measure dietary sodium intake in infancy. Here we review the literature with an aim to describe different methods that have been used for research purposes, how these have been used and their relative strengths and limitations. We identified five studies that were relevant to our aim. In epidemiological and intervention studies sodium intake in infancy has been assessed via parents using diet diaries, which appear to be feasible and acceptable to parents. In these studies, sodium concentration in breast milk is assumed not to vary from one woman to the next, which may not be correct but has been poorly studied. The gold standard method - 24 h urinary excretion of sodium - was used in only one study and there is debate about the most appropriate way to collect urine for research purposes in infants. None of the studies directly compared different methods for determining infant dietary sodium intake. We conclude that research is required to determine the best methods of estimating dietary sodium intake in infants in different research contexts.

Association of diarrhoea in childhood with blood pressure and coronary heart disease in older age: analyses of two UK cohort studies

BACKGROUND

There is a suggestion that acute dehydration in childhood may lead to elevated blood pressure. We examined if episodes of diarrhoea in childhood, a recognized proxy for acute dehydration, were related to measured blood pressure and coronary heart disease in older adults.

METHODS

Data were pooled from two prospective UK cohort studies (participants born 1920-39) in which episodes of diarrhoea were ascertained from health visitor records from birth until 5 years of age. Blood pressure and coronary heart disease were assessed during medical examination in men and women over 64 years of age. In total, 5203 men and women had data on diarrhoea in early life, adult blood pressure and a range of covariates; 4181 of these also had data on coronary heart disease status.

RESULTS

The prevalence of diarrhoea in infancy (3.3%) and between 1 and 5 years (1.1%) was low. There was no relation of diarrhoea from either period (age- and sex-adjusted results for diarrhoea in infancy presented here) with measured blood pressure [coefficient for systolic; 95% CI (confidence interval): 0.44; -2.88-3.76] or coronary heart disease (Odds ratio, OR; 95% CI: 0.91; 0.54-1.54) in adulthood. There was a similar lack of association when hypertension was the outcome of interest. These observations were unchanged after adjustment for a range of covariates.

CONCLUSIONS

In the largest study to date to examine the relation, there was no evidence that diarrhoea in early life had an influence on measured blood pressure, hypertension or coronary heart disease in older adults.

Enhanced nephrogenesis in offspring of water-restricted rat dams

OBJECTIVE

Maternal water restriction (WR) may induce offspring plasma hypertonicity and enhanced vasopressin secretory responses. We determined effects of pregnancy WR on offspring body composition, renal morphology, and blood pressure.

STUDY DESIGN

Pregnant Sprague Dawley rats (n = 21) were randomized to WR, pair-fed (PF), and control from embryo day (e) 10 to e21. Offspring body and organ weights and glomerular number and size were measured at birth and at 21 days of age. At 6 and 9 weeks, offspring blood pressure was determined.

RESULTS

At 21 days of age, WR offspring glomerular number was increased (17%; P < .05), whereas PF glomerular number was lower (4%), compared with controls. Systolic blood pressures were elevated in both WR and PF at both 6 and 9 weeks.

CONCLUSIONS

Pregnancy WR stimulates offspring nephrogenesis, suggesting an adaptive response to future dehydration. Programmed hypertension in WR and PF groups likely occurs via different mechanisms.