Does lower birth order amplify the association between high socioeconomic status and central adiposity in young adult Filipino males?

The differences of lipid profiles between only children and children with siblings: A national survey in China

With the increasing number of the one-child family, it is important to investigate whether the only-child status is associated with dyslipidemia. Among a national sample of 65,347 Chinese children aged 6–17 years, 16,100 lipid profiles were available. Children’s height, weight, total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C) were measured. In comparison to children with siblings, only children (OC) were more likely to be boys and live in urban areas. OC had less physical activity, less fried food intake, but more meat and dairy intakes. OC had significantly higher levels of TC (3.97 ± 0.78 vs. 3.89 ± 0.77) and LDL-C (2.12 ± 0.65 vs. 2.06 ± 0.64) in the overall group, and also in the subgroups of rural boys and girls. The prevalence of hyper-TC (5.48% vs. 4.43%) and hyper-LDL-C (3.97% vs. 2.96%) were significantly higher in OC than their counterparts. Furthermore, we found higher odds of hyper-LDL-C [1.43 (1.12, 1.83)] in OC after adjustments. In the subgroup analysis, only-child status was associated with increased risk of hyper-TC [1.86 (1.06, 3.26)] and hyper-LDL-C [2.65 (1.14, 6.16)] among rural boys, and hyper-LDL-C among rural girls [2.20 (1.14, 4.22)]. In conclusion, higher levels of TC and LDL-C were found in OC especially for rural children. Being an only-child was associated with increased risk of hyper-LDL-C.

A large-scale population study of early life factors influencing left-handedness

Hand preference is a conspicuous variation in human behaviour, with a worldwide proportion of around 90% of people preferring to use the right hand for many tasks, and 10% the left hand. We used the large cohort of the UK biobank (~500,000 participants) to study possible relations between early life factors and adult hand preference. The probability of being left-handed was affected by the year and location of birth, likely due to cultural effects. In addition, hand preference was affected by birthweight, being part of a multiple birth, season of birth, breastfeeding, and sex, with each effect remaining significant after accounting for all others. Analysis of genome-wide genotype data showed that left-handedness was very weakly heritable, but shared no genetic basis with birthweight. Although on average left-handers and right-handers differed for a number of early life factors, all together these factors had only a minimal predictive value for individual hand preference.

Lifetime socioeconomic status and early life microbial environments predict adult blood telomere length in the Philippines

OBJECTIVES

Psychosocial stress is postulated to hasten senescence in part by accelerating the shortening of telomere length (TL). One pathway through which this may happen is via increasing inflammation and innate immune system activation-a pathway which recent studies suggest acts more strongly for those who grew up in low microbial environments. Thus, we hypothesized that: (1) Psychosocial stress will be inversely associated with TL, (2) early life microbial environments will predict TL, and (3) microbial environments will moderate the association between psychosocial stress and TL.

METHODS

We utilized data from the Cebu Longitudinal Health and Nutrition Survey based in the Philippines (N = 1410). We determined early life microbial environments by season of birth and exposure to animal feces. Psychosocial stress measures included perceived stress in adulthood, lifetime socioeconomic status (SES), and parental instability in childhood. TL was measured in blood from young adults by qPCR.

RESULTS

Contrary to predictions, we found that higher SES was associated with shorter TL and no association of TL with the other stress variables. Individuals born in the higher microbial exposure season had shorter TL, but early life microbial environments did not moderate the association between psychosocial stress and TL.

CONCLUSIONS

The unexpected inverse association between SES and TL suggests that higher SES, while indexing lower psychosocial stress, may impact TL more strongly through nonstress factors in the Philippines, such as unhealthy behavior. The inverse association between microbial environments and TL is consistent with other evidence connecting early life infections to decreased life expectancies.

The effects of pre-pregnancy BMI and maternal factors on the timing of adiposity rebound in offspring

OBJECTIVE

To assess the effect of pre-pregnancy body mass index (BMI), gestational weight gain (GWG), and other maternal factors on the timing of adiposity rebound (AR).

METHODS

In this study, 594 mothers (mothers who do not have diabetes and not underweight) from the longitudinal Growth and Obesity Chilean Cohort Study self-reported their weights at the beginning and end of their pregnancies, and their heights were measured. Pre-pregnancy BMI was categorized as normal weight, overweight, or obesity, and GWG was assessed according to Institute of Medicine guidelines. For children, weight and height measurements from 0 to 3 years were retrieved from records, and they were measured from age 4 to 7 years. BMI curves from 0 to 7 years were used to estimate the age at AR, which was categorized as early (<5 years), intermediate (5-7 years), or late (>7 years). The associations between pre-pregnancy BMI and GWG and early AR were tested using logistic regression models.

RESULTS

In total, 33% of the mothers had excess pre-pregnancy weight, 31.2% exceeded Institute of Medicine recommendations, and 45% of children had early AR. The pre-pregnancy BMI and parity were associated with earlier AR (OR = 1.07, 95% CI = 1.02-1.11; OR = 0.86; 95% CI = 0.74-0.99, respectively), but GWG was unrelated.

CONCLUSIONS

These results suggest that preventive strategies for promoting normal pre-pregnancy BMI, especially in women's first pregnancies, could delay the timing of AR, with protective metabolic effects on offspring.

Obesity Among Young Adults in Developing Countries: A Systematic Overview

This article discusses the overweight/obesity situation among young adults in developing countries. For this target population, obesity prevalence ranges from 2.3 to 12 %, and overweight is 28.8 %, mostly affecting females. Weight is now increasing during this life stage of transition at a higher rate, 1 kg/year, than in developed countries. Maternal factors and early childhood socioeconomic status are associated with BMI in young adults along with changing environmental and behavioural factors in some low and middle income countries, brought about by demographic and socioeconomic transitions. Young adults with 'normal weight' obesity need identification using other convenient low cost measures (skin folds or waist circumference) along with BMI. Obesity prevention or management interventions were not identified, but clearly needed to help stem the obesity pandemic. Young people generally give little priority to their future health, so such interventions need to be conducted at some optimal age, be innovative, country specific and culturally acceptable.

Association between Maternal Smoking during Pregnancy and Low Birthweight: Effects by Maternal Age

Background

Maternal smoking during pregnancy has been consistently related to low birthweight. However, older mothers, who are already at risk of giving birth to low birthweight infants, might be even more susceptible to the effects of maternal smoking. Therefore, this study aimed to examine the modified association between maternal smoking and low birthweight by maternal age.

Methods

Data were obtained from a questionnaire survey of all mothers of children born between 2004 and 2010 in Okinawa, Japan who underwent medical check-ups at age 3 months. Variables assessed were maternal smoking during pregnancy, maternal age, gestational age, parity, birth year, and complications during pregnancy. Stratified analyses were performed using a logistic regression model.

Results

In total, 92641 participants provided complete information on all variables. Over the 7 years studied, the proportion of mothers smoking during pregnancy decreased from 10.6% to 5.0%, while the prevalence of low birthweight did not change remarkably (around 10%). Maternal smoking was significantly associated with low birthweight in all age groups. The strength of the association increased with maternal age, both in crude and adjusted models.

Conclusions

Consistent with previous studies conducted in Western countries, this study demonstrates that maternal age has a modifying effect on the association between maternal smoking and birthweight. This finding suggests that specific education and health care programs for older smoking mothers are important to improve their foetal growth.

The influence of birth order and number of siblings on adolescent body composition: evidence from a Brazilian birth cohort study

The aim of this study was to estimate the association between birth order and number of siblings with body composition in adolescents. Data are from a birth cohort study conducted in Pelotas, Brazil. At the age of 18 years, 4563 adolescents were located, of whom 4106 were interviewed (follow-up rate 81·3 %). Of these, 3974 had complete data and were thus included in our analysis. The variables used in the analysis were measured during the perinatal period, or at 11, 15 and/or 18 years of age. Body composition at 18 years was collected by air displacement plethysmography (BOD POD^®). Crude and adjusted analyses of the association between birth order and number of siblings with body composition were performed using linear regression. All analyses were stratified by the adolescent sex. The means of BMI, fat mass index and fat-free mass index among adolescents were 23·4 (sd 4·5) kg/m², 6·1 (sd 3·9) kg/m² and 17·3 (sd 2·5) kg/m², respectively. In adjusted models, the total siblings remained inversely associated with fat mass index (β = − 0·37 z-scores, 95 % CI − 0·52, − 0·23) and BMI in boys (β = − 0·39 z-scores, 95 % CI − 0·55, − 0·22). Fat-free mass index was related to the total siblings in girls (β = 0·06 z-scores, 95 % CI − 0·04, 0·17). This research has found that number of total siblings, and not birth order, is related to the fat mass index, fat-free mass index and BMI in adolescents. It suggests the need for early prevention of obesity or fat mass accumulation in only children.

The association of birth order with later body mass index and blood pressure: a comparison between prospective cohort studies from the United Kingdom and Brazil

Background:

Previous studies have found greater adiposity and cardiovascular risk in first born children. The causality of this association is not clear. Examining the association in diverse populations may lead to improved insight.

Methods:

We examine the association between birth order and body mass index (BMI), systolic and diastolic blood pressure (SBP/DBP) in the 2004 Pelotas cohort from southern Brazil and the Avon Longitudinal Study of Parents and Children (ALSPAC) from Bristol, south-west England, restricting analysis to families with two children in order to remove confounding by family size.

Results:

No consistent differences in BMI, SBP or DBP were observed comparing first and second born children. Within the Pelotas 2004 cohort, first born females were thinner, with lower SBP and DBP; for example, mean difference in SBP comparing first with second born was −0.979 (95% confidence interval −2.901 to 0.943). In ALSPAC, first born females had higher BMI, SBP and DBP. In both cohorts, associations tended to be in the opposite direction in males, although no statistical evidence for gender interactions was found.

Conclusions:

The findings do not support an association between birth order and BMI or blood pressure. Differences to previous studies may be explained by differences in populations and/or confounding by family size in previous studies.

Birth order progressively affects childhood height

BACKGROUND

There is evidence suggesting that first-born children and adults are anthropometrically different to later-borns. Thus, we aimed to assess whether birth order was associated with changes in growth and metabolism in childhood.

METHODS

We studied 312 healthy prepubertal children: 157 first-borns and 155 later-borns. Children were aged 3-10 years, born 37-41 weeks gestation, and of birth weight appropriate-for-gestational-age. Clinical assessments included measurement of children's height, weight, fasting lipid and hormonal profiles and DEXA-derived body composition.

RESULTS

First-borns were taller than later-borns (P < 0·0001), even when adjusted for parents' heights (0·31 vs 0·03 SDS; P = 0·001). There was an incremental height decrease with increasing birth order, so that first-borns were taller than second-borns (P < 0·001), who were in turn taller than third-borns (P = 0·007). Further, among sibling pairs both height SDS (P = 0·009) and adjusted height SDS (P < 0·0001) were lower in second- vs first-born children. Consistent with differences in stature, first- (P = 0·043) and second-borns (P = 0·003) had higher IGF-I concentrations than third-borns. Both first- (P < 0·001) and second-borns (P = 0·004) also had reduced abdominal adiposity (lower android fat to gynoid fat ratio) when compared with third-borns. Other parameters of adiposity and blood lipids were unaffected by birth order.

CONCLUSIONS

First-borns were taller than later-born children, with an incremental height reduction from first to third birth order. These differences were present after correction for genetic height, and associated to some extent with alterations in plasma IGF-I. Our findings strengthen the evidence that birth order is associated with phenotypic changes in childhood.

Association of birth order with cardiovascular disease risk factors in young adulthood: a study of one million Swedish men

Background

Birth order has been suggested to be linked to several cardiovascular disease (CVD) risk factors, but the evidence is still inconsistent. We aim to determine the associations of birth order with body mass index (BMI), muscle strength and blood pressure. Further we will analyse whether these relationships are affected by family characteristics.

Methods

BMI, elbow flexion, hand grip and knee extension strength and systolic and diastolic blood pressure were measured at conscription examination in 1 065 710 Swedish young men born between 1951 and 1975. The data were analysed using linear multivariate and fixed effects regression models; the latter compare siblings and account for genetic and social factors shared by brothers.

Results

Fixed effect regression analysis showed that birth order was inversely associated with BMI: second and third born had 0.8% and 1.1% (p<0.001) lower BMI than first-born, respectively. The association pattern differed among muscle strengths. After adjustment for BMI, first-born presented lower elbow flexion and hand grip strength than second-born (−5.9 N and −3.8 N, respectively, p<0.001). Knee extension strength was inversely related to birth order though not always significantly. The association between birth order and blood pressure was not significant.

Conclusions

Birth order is negatively associated with BMI and knee extension strength, positively with elbow flexion and hand grip strength, and is not associated with blood pressure among young men. Although the effects are small, the link between birth order and some CVD risk factors is already detectable in young adulthood.

First-born children have reduced insulin sensitivity and higher daytime blood pressure compared to later-born children

BACKGROUND

Evidence suggests that first-born children and adults are phenotypically different to later-born children. Therefore, we aimed to assess whether birth order would be associated with changes in metabolism in childhood.

METHODS

We studied 85 healthy prepubertal children aged 4 to 11 years, born 38 to 40 weeks' gestation, and birth weight appropriate for gestational age: 32 first-born and 53 later-born children. Clinical assessments included measurement of children's height, weight, fasting lipid and hormonal profiles, and dual-energy x-ray absorptiometry-derived body composition. Children also underwent 24-hour ambulatory blood pressure monitoring, and frequently sampled intravenous glucose tests with Bergman's minimal model.

RESULTS

First-born children were approximately 3 cm taller (height SD scores 0.88 vs 0.39; P = .009) and were slimmer (body mass index SD scores -0.05 vs 0.39; P = .048) than later-born children. Consistent with their taller stature, first-born children also had a 27% increase in IGF-I concentrations (227 vs 173 ng/mL; P = .002). Insulin sensitivity was reduced by 21% among first-borns compared to later-borns (8.4 vs 10.6 × 10(-4)/min/[mU/L]; P = .019). Further, 24-hour ambulatory blood pressure monitoring showed that first-borns had higher daytime systolic (+5 mm Hg; P = .032) and diastolic (+4 mm Hg; P = .029) blood pressure. Blood lipids were unaffected by birth order.

CONCLUSIONS

Although first-borns were taller and slimmer, these children had reduced insulin sensitivity and increased daytime blood pressure compared to later-borns. Thus, first-borns may be at a greater risk of metabolic and cardiovascular diseases in adult life. This finding may have important public health implications, in light of a worldwide trend toward smaller families.

Being an only or last-born child increases later risk of obesity

BACKGROUND

Studies have suggested that number of siblings and birth order is associated with obesity. However, studies combining these exposures are needed. This study aimed at investigating obesity in children and young adults in regard to different combinations of family size and birth order.

METHODS

Two cohorts selected from the general population were investigated: The Copenhagen School Health Records Register (CSHRR) and a Draft Board (DB) sample with measured heights and weights in childhood (age 13 years) and young adulthood (age 19 years), respectively. Information on birth order, number of siblings, and relevant covariates were available on 29 327 children, as well as on 323 obese young men and 575 randomly selected controls of young men representing approximately 58 000. The relation between number of siblings and birth order, respectively, and having a Body Mass Index (BMI) z-score above or equal to the 95(th) percentile in childhood or having a BMI of at least 31.00 kg/m(2) in young adulthood was analysed using logistic regression analyses adjusted for relevant confounders.

RESULTS

Only children had significantly higher odds of obesity both in childhood and in young adulthood compared with children with siblings, odds ratio (OR) =1.44 (95% Confidence Interval (CI): 1.26-1.66) and OR=1.76 (95% CI: 1.18-2.61), respectively. No association between first-born status and obesity was found. The OR of last-born children being obese was also significantly increased in childhood, e.g. OR=1.93 (95% CI: 1.09-3.43) of obesity if last-born in a family of four children. This was not found in young adulthood. Additionally, higher spacing to previous sibling (average 1872 vs. 1303 days; p=0.026 in four children families) was observed in obese last-born compared to non-obese last-born children.

CONCLUSION

Being an only or last-born child is associated with obesity. These associations may provide leads to targeted prevention of obesity in children.

Associations of birth order with early growth and adolescent height, body composition, and blood pressure: prospective birth cohort from Brazil

Birth weight has been inversely associated with later blood pressure. Firstborns tend to have lower birth weight than their later-born peers, but the long-term consequences remain unclear. The study objective was to investigate differences between firstborn and later-born individuals in early growth patterns, body composition, and blood pressure in Brazilian adolescents. The authors studied 453 adolescents aged 13.3 years from the prospective 1993 Pelotas Birth Cohort. Anthropometry, blood pressure, physical activity by accelerometry, and body composition by deuterium were measured. Firstborns (n = 143) had significantly lower birth weight than later borns (n = 310). At 4 years, firstborns had significantly greater weight and height, indicating a substantial overshoot in catch-up growth. In adolescence, firstborns had significantly greater height and blood pressure and a lower activity level. The difference in systolic blood pressure could be attributed to variability in early growth and that in diastolic blood pressure to reduced physical activity. The magnitude of increased blood pressure is clinically significant; hence, birth order is an important developmental predictor of cardiovascular risk in this population. Firstborns may be more sensitive to environmental factors that promote catch-up growth, and this information could potentially be used in nutritional management to prevent catch-up “overshoot.”