Fetal and infant growth patterns and kidney function at school age

Association of linear growth velocities between 0 and 6 years with kidney function and size at 10 years: A birth cohort study in Ethiopia

BACKGROUND

Risk of noncommunicable diseases accrues from fetal life, with early childhood growth having an important role in adult disease risk. There is a need to understand how early-life growth relates to kidney function and size.

OBJECTIVES

This study aimed to assess the association of linear growth velocities among children between 0 and 6 y with kidney function and size among children aged 10 y.

METHODS

The Ethiopian Anthropometric and Body Composition birth cohort recruited infants born at term to mothers living in Jimma with a birth weight of ≥1500 g and without congenital malformations. Participants were followed up with 13 measurements between birth and 6 y of age. The latest follow-up was at ages 7-12 y with measurement of serum cystatin C as a marker of kidney function and ultrasound assessment of kidney dimensions. Kidney volume was computed using an ellipsoid formula. Linear-spline multilevel modeling was used to compute linear growth velocities between 0 and 6 y. Multiple linear regression modeling was used to examine the associations of linear growth velocities in selected age periods with cystatin C and kidney size.

RESULTS

Data were captured from 355 children, at a mean age of 10 (range 7-12) y. The linear growth velocity was high between 0 and 3 mo and then decreased with age. There was no evidence of an association of growth velocity ≤24 mo with cystatin C at 10 y. Between 24 and 48 and 48 and 76 mo, serum cystatin C was higher by 2.3% [95% confidence interval (CI): 0.6, 4.2] and 2.1% (95% CI: 0.3, 4.0) for 1 SD higher linear growth velocity, respectively. We found a positive association between linear growth velocities at all intervals between 0 and 6 y and kidney volume.

CONCLUSIONS

Greater linear growth between 0 and 6 y of development was positively associated with kidney size, and greater growth velocity after 2 y was associated with higher serum cystatin C concentrations.

Ethnic differences in kidney function in childhood: the Born in Bradford Cohort Renal Study

Background: Endstage kidney failure rates are higher in South Asians than in White Europeans. Low birth weight is associated with adult chronic kidney disease and is more common in South Asians. Foetal kidney size was smaller in South Asians in the Born in Bradford (BiB) birth cohort. As part of BiB follow up, we aimed to investigate if there were ethnic differences in kidney function and blood pressure in early childhood and whether this was different by foetal kidney size. Methods: Serum creatinine, cystatin C, urea, and urinary albumin to creatinine ratio (ACR), protein to creatinine ratio (PCR) and retinol binding protein (RBP) were analysed in blood and urine samples from those who participated in the BiB follow-up at 7-11 years. Ethnicity was categorised by parental self-report as White European and South Asian. Estimated glomerular filtration rate (eGFR) was calculated using Schwartz, and cystatin C Zappitelli and Filler equations. Linear regression was used to examine the association between ethnicity and eGFR, PCR and blood pressure. Results: 1591 children provided blood (n=1403) or urine (n=625) samples. Mean eGFR was 92 ml/min/1.73m 2 (standard deviation (SD) 9) using Schwartz (n=1156) and 94 (SD 11) using Zappitelli (n=1257). CKD prevalence was rare (1 with eGFR <60 ml/min/1.73m 2, 14 (2.4%) had raised ACR (>2.5 mg/mmol in boys/3.5 mg/mmol in girls). Diastolic blood pressure was higher in South Asian children (difference 2.04 mmHg, 95% CI 0.99 to 3.10) but was not significant in adjusted analysis. There was no evidence of association in adjusted models between ethnicity and any eGFR or urinary measure at this age. Conclusions: There was no evidence of significant ethnic differences in kidney function at pre-pubertal age despite differences in kidney volume at birth. Longitudinal follow-up is required to track ethnic patterns in kidney function and blood pressure as children develop through puberty.

Role of foetal kidney size on kidney function in childhood: the born in bradford cohort renal study

BACKGROUND

Foetal and early childhood development contributes to the risk of adult non-communicable diseases such as hypertension and cardiovascular disease. We aimed to investigate whether kidney size at birth is associated with markers of kidney function at 7-11 years.

METHODS

Foetal kidney dimensions were measured using ultrasound scans at 34 weeks gestation and used to derive kidney volume (cm3) in 1802 participants in the Born in Bradford (BiB) birth cohort. Blood and urine samples were taken from those who participated in the BiB follow-up at 7-11 years (n = 630) and analysed for serum creatinine, cystatin C, urea, and urinary albumin to creatinine ratio (ACR), protein to creatinine ratio (PCR) and retinol binding protein (RBP). Estimated glomerular filtration rate (eGFR) was calculated using Schwartz creatinine only and combined with cystatin C, and cystatin C only Zappitelli and Filler equations. Linear regression was used to examine the association between foetal kidney volume and eGFR, ACR, PCR and blood pressure, unadjusted and adjusted for confounders.

RESULTS

Kidney volume was positively associated in adjusted models with eGFR calculated using Schwartz combined (0.64 ml/min diff per unit increase in volume, 95% CI 0.25 to 1.02), Zappitelli (0.79, 95% CI 0.38 to 1.20) and Filler (2.84, 95% CI 1.40 to 4.28). There was an association with the presence of albuminuria but not with its level, or with other urinary markers or with blood pressure.

CONCLUSION

Foetal kidney volume was associated with small increases in eGFR in mid-childhood. Longitudinal follow-up to investigate the relationship between kidney volume and markers of kidney function as children go through puberty is required.

Effect of Protein Intake Early in Life on Kidney Volume and Blood Pressure at 11 Years of Age

High protein intake has been associated with kidney hypertrophy, which is usually reversible; however, when it occurs early in life, it could lead to cell programming with a long-lasting effect. This study aimed to assess whether higher protein ingestion early in life has a persistent effect on kidney volume at 11 years of age, as well as its influence on blood pressure. This is a secondary analysis of a randomized control trial that compared the growth of infants fed with a higher-protein formula versus those fed with a lower-protein formula, with a control group of breastfed infants. Renal ultrasound and anthropometric measurements were assessed at 6 months and 11 years of age. At 11 years, urinary protein, albumin and creatinine, and blood pressure were measured in 232 children. Feeding with a higher-protein formula was associated with a larger kidney volume (β = 8.71, 95%CI 0.09-17.33, p = 0.048) and higher systolic blood pressure (β = 3.43, 95%CI 0.78-6.08, p = 0.011) at 11 years of age. Microalbuminuria was detected in 7% of the patients, with no differences among groups (p = 0.56). The effect of increased protein ingestion early in life may condition kidney volume and blood pressure in later childhood.

Preterm Birth, Kidney Function and Cardiovascular Disease in Children and Adolescents

Over recent decades, there has been a global increase in preterm birth rate, which constitutes about 11% of total births worldwide. The present review aims to summarize the current knowledge on the long-term consequences of prematurity on renal and cardiovascular development and function. Recent literature supports that prematurity, intrauterine growth restriction or low birth weight (LBW) may have an adverse impact on the development of multiple organ systems, predisposing to chronic diseases in childhood and adulthood, such as arterial hypertension and chronic kidney disease. According to human autopsy and epidemiological studies, children born preterm have a lower nephron number, decreased kidney size and, in some cases, affected renal function. The origin of hypertension in children and adults born preterm seems to be multifactorial as a result of alterations in renal, cardiac and vascular development and function. The majority of the studies report increased systolic and diastolic blood pressure (BP) in individuals born preterm compared to full term. The early prevention and detection of chronic non-communicable diseases, which start from childhood and track until adulthood in children with a history of prematurity or LBW, are important.

Mismatch between poor fetal growth and rapid postnatal weight gain in the first 2 years of life is associated with higher blood pressure and insulin resistance without increased adiposity in childhood: the GUSTO cohort study

BACKGROUND

Using longitudinal ultrasounds as an improved fetal growth marker, we aimed to investigate if fetal growth deceleration followed by rapid postnatal weight gain is associated with childhood cardiometabolic risk biomarkers in a contemporary well-nourished population.

METHODS

We defined fetal growth deceleration (FGD) as ultrasound-measured 2nd-3rd-trimester abdominal circumference decrease by ≥0.67 standard deviation score (SDS) and rapid postnatal weight gain (RPWG) as 0-2-year-old weight increase by ≥0.67 SDS. In the GUSTO mother-offspring cohort, we grouped 797 children into four groups of FGD-only (14.2%), RPWG-only (23.3%), both (mismatch, 10.7%) or neither (reference, 51.8%). Adjusting for confounders and comparing with the reference group, we tested associations of these growth groups with childhood cardiometabolic biomarkers: magnetic resonance imaging (MRI)-measured abdominal fat (n = 262), liver fat (n = 216), intramyocellular lipids (n = 227), quantitative magnetic resonance-measured overall body fat % (BF%) (n = 310), homeostasis model assessment of insulin resistance (HOMA-IR) (n = 323), arterial wall thickness (n = 422) and stiffness (n = 443), and blood pressure trajectories (ages 3-6 years).

RESULTS

Mean±SD birthweights were: FGD-only (3.11 ± 0.38 kg), RPWG-only (3.03 ± 0.37 kg), mismatch (2.87 ± 0.31 kg), reference (3.30 ± 0.36 kg). FGD-only children had elevated blood pressure trajectories without correspondingly increased BF%. RPWG-only children had altered body fat partitioning, higher BF% [BF = 4.26%, 95% confidence interval (CI) (2.34, 6.19)], HOMA-IR 0.28 units (0.11, 0.45)] and elevated blood pressure trajectories. Mismatch children did not have increased adiposity, but had elevated ectopic fat, elevated HOMA-IR [0.29 units (0.04,0.55)] and the highest blood pressure trajectories. Associations remained even after excluding small-for-gestational-age infants from analyses.

CONCLUSIONS

Fetal growth deceleration coupled with rapid postnatal weight gain was associated with elevated childhood cardiometabolic risk biomarkers without correspondingly increased BF%.

Clinical consequences of developmental programming of low nephron number

Nephron number in humans varies up to 13-fold, likely reflecting the impact of multiple factors on kidney development, including inherited body size and ethnicity, as well as maternal health and nutrition, fetal exposure to gestational diabetes or preeclampsia and other environmental factors, which may potentially be modifiable. Such conditions predispose to low or high offspring birth weight, growth restriction or preterm birth, which have all been associated with increased risks of higher blood pressures and/or kidney dysfunction in later life. Low birth weight, preterm birth, and intrauterine growth restriction are associated with reduced nephron numbers. Humans with hypertension and chronic kidney disease tend to have fewer nephrons than their counterparts with normal blood pressures or kidney function. A developmentally programmed reduction in nephron number therefore enhances an individual's susceptibility to hypertension and kidney disease in later life. A low nephron number at birth may not lead to kidney dysfunction alone except when severe, but in the face of superimposed acute or chronic kidney injury, a kidney endowed with fewer nephrons may be less able to adapt, and overt kidney disease may develop. Given that millions of babies are born either too small, too big or too soon each year, the population impact of altered renal programming is likely to be significant. Many gestational exposures are modifiable, therefore urgent attention is required to implement public health measures to optimize maternal, fetal, and child health, to prevent or mitigate the consequences of developmental programming, to improve the health future generations.

Features of and preventive measures against hypertension in the young

The Japanese hypertension guidelines report that essential hypertension is detected in 1–3% of upper elementary and high school students during blood pressure (BP) screenings. Hypertension in these age groups is an emerging public health concern mainly attributed to the rising rate of pediatric obesity. Considering the existence of BP tracking phenomenon, early preventive education and instruction are necessary, especially for male students with moderately elevated BP showing a tendency toward obesity, despite the low prevalence of hypertension in high school students. Students with a positive family history of hypertension and those born with low birth weight need the same measures. Lifestyle habits, such as increased alcohol intake, dramatically change once students begin university; thus, early education and instruction regarding the factors influencing BP are necessary. In particular, for male students with higher BP during high school, caution regarding increased body weight is required irrespective of their level of obesity. Young adults aged <40 years should be educated about the association between body weight and hypertension. Particular caution surrounding lifestyle habits, including drinking and smoking, is warranted in male hypertensive subjects because hypertension at a young age is strongly associated with obesity. BP monitoring and the management of obesity should be considered efficient approaches to the detection and treatment of hypertension. For the lifetime prevention of hypertension, it is essential to be aware of one’s health status and learn about healthy lifestyles beginning in childhood. BP measurement may be an appropriate means to achieve this goal.

Effect of early postnatal nutrition on chronic kidney disease and arterial hypertension in adulthood: a narrative review

Intrauterine growth restriction (IUGR) has been identified as a risk factor for adult chronic kidney disease (CKD), including hypertension (HTN). Accelerated postnatal catch-up growth superimposed to IUGR has been shown to further increase the risk of CKD and HTN. Although the impact of excessive postnatal growth without previous IUGR is less clear, excessive postnatal overfeeding in experimental animals shows a strong impact on the risk of CKD and HTN in adulthood. On the other hand, food restriction in the postnatal period seems to have a protective effect on CKD programming. All these effects are mediated at least partially by the activation of the renin-angiotensin system, leptin and neuropeptide Y (NPY) signaling and profibrotic pathways. Early nutrition, especially in the postnatal period has a significant impact on the risk of CKD and HTN at adulthood and should receive specific attention in the prevention of CKD and HTN.

Temporal trends in renal function and birthweight in Japanese adolescent males (1998-2015)

Background

Low birthweight (LBW) is a worldwide public health problem, demonstrating an increasing incidence in developed countries, including Japan. LBW is also a risk factor for later development of chronic kidney disease (CKD). To date, studies have not evaluated the population impacts of increasing LBW rates on renal function.

Methods

Estimated glomerular filtration rate (eGFR) was evaluated in 3737 Japanese adolescent males (15–16 years old) using annual cross-sectional data over an 18-year period (1998–2015).

Results

Between the initial (1998–2003) and final (2010–15) periods of the study, the mean birthweight decreased from 3213.4 ± 383.8 to 3116.2 ± 382.3 g and the LBW rate increased from 2.5 to 5.5% (both P ≤ 0.01). Additionally, the mean eGFR decreased from 105.1 ± 15.9 to 97.4 ± 13.8 mL/min/1.73 m² and the prevalence of mildly reduced renal function (eGFR ≤ 60– <90 mL/min/1.73 m²) increased from 16.4 to 30.0% (both P ≤ 0.01), most evident in the LBW group (from 10.3 to 41.7%, P ≤0.01). The prevalence of proteinuria also increased significantly. Mildly reduced renal function was significantly associated with LBW [odds ratio (LBW 3000–3999 g) 1.51; 95% confidence interval 1.00–2.55; P = 0.047].

Conclusions

In this population of Japanese adolescents, the frequency of mildly reduced renal function increased as the LBW frequency increased. Our findings may have implications for the broader Japanese population as well as for other populations in which the prevalence of LBW is increasing.

Reference ranges and impact of selected confounders on classic serum and urinary renal markers in neonatal period

PURPOSE

Renal injury in term and pre-term neonates may be an antecedent to chronic kidney disease in the child's further life. The aim of the paper was to compile a reference range for selected serum and urinary renal markers in the neonatal period for full-term (FT) and pre-term (PT) newborns.

MATERIAL AND METHODS

The prospective study included 23 FT infants (birth weight - BW≥2500g and gestational age - GA≥37Hbd) and 32 PT children (BW<2500g and GA<37Hbd) in good general condition, without acute kidney injury (AKI) or sepsis. Between the 4th and 28th DOL, urinary concentrations of the studied renal markers (uCr, uNa, uOsm) were determined on a daily basis, while serum creatinine (SCr) was assessed minimum every 48-72h.

RESULTS

The mean GA and BW of the FT and PT infants were respectively as follows: 38.5±1.7Hbd; 3433±495.2g and 32.7±2.6Hbd; 1836.7±419.8g. For serum glomerular (SCr, eGFR) and tubular markers (FENa, RFI), the median values with normal ranges were compiled. For urinary renal markers (uCr, uNa, uOsm) and those values standardized for kg of body weight, percentile tables for 4-28DOL were elaborated.

CONCLUSIONS

The study has resulted in determining the normal ranges of serum glomerular and tubular renal markers, as well as percentile tables of selected urinary renal parameters during the neonatal period. The percentile tables may prove to be helpful for further standardization of other urinary parameters per urinary creatinine in neonatal population.

Effect of birth weight on adulthood renal function: A bias-adjusted meta-analytic approach

While the association between low birth weight (LBW; <2500 g) and development of adult chronic renal disease (CKD) is inconsistently reported, less information is available regarding association of high birth weight (HBW; ≥4000 g) with CKD. We undertook a systematic review and meta-analysis on studies published before 30 September 2015 and report associations between birth weight and renal function. Blood (glomerular filtration rate (GFR)) and urine (microalbuminuria/albumin excreation rate (AER)/urinary albumin creatinine ratio (ACR)) parameters were used to define CKD. Three different effect size estimates were used (odds ratio, regression coefficient and mean difference). The odds of developing CKD in the life course among those born LBW was 1.77 (95% CI: 1.42, 2.20) times and 1.68 (1.27, 2.33) times, assessed by blood and urine parameters respectively. Higher risk was also observed among Asian and Australian populations (blood: OR 2.68; urine: OR 2.28), individuals aged ≤30 years (blood: OR 2.30; urine: OR 1.26), and ≥50 years (blood: OR 3.66; urine: OR 3.10), people with diabetes (blood: OR 2.51), and aborigines (urine: OR 2.32). There was no significant association between HBW and CKD. For every 1 kg increase in BW, the estimated GFR increased by 2.09 mL/min per 1.73 m(2) (1.33-2.85), and it was negatively associated with LogACR (ß -0.07, 95% CI: -0.14, 0.00). LBW inborn had lower mean GFR -4.62 (-7.10, -2.14) compared with normal BW. Findings of this study suggest that LBW increased the risk of developing CKD, and HBW did not show any significant impact.

Fetal first trimester growth is not associated with kidney outcomes in childhood

BACKGROUND

Impaired fetal growth is associated with increased risks of kidney diseases in later life. Because human development rates are highest during the first trimester, this trimester may be a particularly critical period for kidney outcomes. We have therefore examined the association of fetal first trimester growth with kidney outcomes in childhood.

METHODS

This study was embedded in a prospective population-based cohort study among 1176 pregnant women and their children. We used fetal first trimester crown-length as the growth measure among mothers with a regular menstrual cycle and a known first day of the last menstrual period. At the childhood age of 6 (median 5.7-6.8) years, we measured combined kidney volume, microalbuminuria and estimated glomerular filtration rate (eGFR) based on serum creatinine and cystatin C concentrations.

RESULTS

No consistent associations of fetal first trimester crown-rump length with childhood combined kidney volume, eGFR and microalbuminuria were observed. Compared to children with a fetal first trimester crown-rump length in the highest quintile, those in the lowest quintile had a larger childhood combined kidney volume (difference 5.32 cm³, 95 % confidence interval 1.06 to 9.57), but no differences in kidney function.

CONCLUSION

Our results do not support the hypothesis that fetal first trimester growth restriction affects kidney size and function in childhood. Further studies are needed to focus on critical periods in early life for kidney function and disease in later life.

Influence of common genetic variants on childhood kidney outcomes

BACKGROUND

Kidney measures in early life are associated with kidney disease in later life. We hypothesized that these associations are partly explained by common genetic variants that lead to both smaller kidneys with lower kidney function in early childhood and kidney disease in adulthood.

METHODS

We examined in a population-based prospective cohort study among 4,119 children the associations of a weighted genetic risk score combining 20 previously identified common genetic variants related to adult eGFRcreat with kidney outcomes in children aged 6.0 years (95% range 5.7-7.8). Childhood kidney outcomes included combined kidney volume, glomerular filtration rate (eGFR) based on creatinine levels, and microalbuminuria based on albumin and creatinine urine levels.

RESULTS

We observed that the genetic risk score based on variants related to impaired kidney function in adults was associated with a smaller combined kidney volume (P value 3.0 × 10(-3)) and with a lower eGFR (P value 4.0 × 10(-4)) in children. The genetic risk score was not associated with microalbuminuria.

CONCLUSION

Common genetic variants related to impaired kidney function in adults already lead to subclinical changes in childhood kidney outcomes. The well-known associations of kidney measures in early life with kidney disease in later life may at least be partly explained by common genetic variants.

Signs and symptoms of developmental abnormalities of the genitourinary tract

OBJECTIVE

The abnormalities of the genitourinary tract development are the leading cause of chronic kidney disease (CKD) in children. The diagnosis of this disease in Brazil is late and incomplete, which results in increased morbidity and mortality in this age group. Early diagnosis of this condition is the prerogative of generalist pediatricians, and the aim of this study was to review the clinical signs and symptoms associated with developmental abnormalities of the genitourinary tract.

DATA SOURCES

Based on the description of a symbolic clinical case, the authors conducted a non-systematic review of medical literature.

DATA SYNTHESIS

The results suggest that the following data should be used as a warning for early diagnosis of affected children: (a) combined urinary tract abnormalities (chromosomal abnormalities; sequence of malformations [VACTERLand Prune-Belly]; and musculoskeletal, digestive tract, heart, and nervous system malformations); (b) previous history (congenital anomalies of the kidney and urinary tract [CAKUT] in the family, low birth weight, and oligoamnios); (c) clinical signs (polyuria/nocturia, urinary tract infection, systemic arterial hypertension, failure to thrive, weak urinary stream, difficulty to start urination, distended bladder, non-monosymptomatic enuresis, urinary/urge incontinence, and bowel and bladder dysfunction); and (d) pre- and postnatal ultrasonographic alterations (increased anteroposterior diameter of the renal pelvis, mainly in the third trimester of pregnancy; single kidney; hydronephrosis associated with other abnormalities; and hydronephrosis with parenchymal involvement in the post-neonatal assessment).

CONCLUSION

The suggestions shown here can help the pediatrician to establish clinical hypotheses for the early diagnosis of developmental abnormalities of the genitourinary tract without resorting to expensive and invasive procedures.

Infant Breastfeeding and Kidney Function in School-Aged Children

BACKGROUND

Early life factors may influence kidney growth and function throughout the life course. We examined the associations of breastfeeding duration and exclusivity and age at introduction of solid foods with kidney outcomes at school age.

STUDY DESIGN

Prospective cohort study from fetal life onward.

SETTING & PARTICIPANTS

5,043 children in the Netherlands.

PREDICTORS

Infant feeding was assessed prospectively using questionnaires.

OUTCOMES & MEASUREMENTS

In children at a median age of 6.0 years, we measured kidney volume with ultrasound, estimated glomerular filtration rate (eGFR) from serum creatinine level, and microalbuminuria from urinary albumin and creatinine levels.

RESULTS

92% of all children were ever breastfed, of whom 27% were breastfed for more than 6 months and 21% were breastfed exclusively for at least 4 months. Compared with ever-breastfed children, never-breastfed children had smaller combined kidney volumes (-2.69 [95% CI, -4.83 to -0.56] cm(3)) and lower eGFRs (-2.42 [95% CI, -4.56 to -0.28] mL/min/1.73 m(2)) at school age. Among breastfed children, shorter duration of breastfeeding was associated with smaller combined kidney volume and lower microalbuminuria risk (P<0.05). Compared to exclusive breastfeeding for 4 months, nonexclusive breastfeeding in the first 4 months was associated with smaller combined kidney volume and lower eGFR (both P<0.05). Associations with eGFR were explained largely by kidney volume. Age at introduction of solid foods was not associated with any kidney outcome.

LIMITATIONS

Observational study, so causality cannot be established. Follow-up measurements were available for 76% of children.

CONCLUSIONS

These results suggest that breastfeeding is associated with subclinical changes in kidney outcomes in childhood. Further studies are needed to explore whether early life nutrition also affects the risk of kidney disease in adulthood.

Birth weight, malnutrition and kidney-associated outcomes--a global concern

An adverse intrauterine environment is associated with an increased risk of elevated blood pressure and kidney disease in later life. Many studies have focused on low birth weight, prematurity and growth restriction as surrogate markers of an adverse intrauterine environment; however, high birth weight, exposure to maternal diabetes and rapid growth during early childhood are also emerging as developmental risk factors for chronic diseases. Altered programming of nephron number is an important link between exposure to developmental stressors and subsequent risk of hypertension and kidney disease. Maternal, fetal, and childhood nutrition are crucial contributors to these programming effects. Resource-poor countries experience the sequential burdens of fetal and childhood undernutrition and subsequent overnutrition, which synergistically act to augment the effects of developmental programming; this observation might explain in part the disproportionate burden of chronic disease in these regions. Numerous nutritional interventions have been effective in reducing the short-term risk of low birth weight and prematurity. Understanding the potential long-term benefits of such interventions is crucial to inform policy decisions to interrupt the developmental programming cycle and stem the growing epidemics of hypertension and kidney disease worldwide.

Protein intake in infancy and kidney size and function at the age of 6 years: The Generation R Study

BACKGROUND

High protein intake has been linked to kidney growth and function. Whether protein intake is related to kidney outcomes in healthy children is unclear.

METHODS

We examined the associations between protein intake in infancy and kidney outcomes at age 6 years in 2968 children participating in a population-based cohort study. Protein intake at 1 year was assessed using a food-frequency questionnaire and was adjusted for energy intake. At age 6 years we measured the kidney volume and urinary albumin/creatinine ratio (ACR) of all participating children, and we estimated glomerular filtration rate (eGFR) using serum creatinine and cystatin C levels.

RESULTS

In models adjusted for age, sex, body surface area, and sociodemographic factors, a higher protein intake was associated with a lower ACR and a higher eGFR but was not consistently associated with kidney volume. However, after further adjustment for additional dietary and lifestyle factors, such as sodium intake, diet quality, and television watching, higher protein intake was no longer associated with kidney function. No differences in associations were observed between animal and vegetable protein intake.

CONCLUSIONS

Our findings show that protein intake in early childhood is not independently associated with kidney size or function at the age of 6 years. Further study is needed on other early life predictors of kidney size and function in later life.

The Generation R Study: Biobank update 2015

The Generation R Study is a population-based prospective cohort study from fetal life until adulthood. The study is designed to identify early environmental and genetic causes and causal pathways leading to normal and abnormal growth, development and health from fetal life, childhood and young adulthood. In total, 9,778 mothers were enrolled in the study. Data collection in children and their parents include questionnaires, interviews, detailed physical and ultrasound examinations, behavioural observations, Magnetic Resonance Imaging and biological samples. Efforts have been conducted for collecting biological samples including blood, hair, faeces, nasal swabs, saliva and urine samples and generating genomics data on DNA, RNA and microbiome. In this paper, we give an update of the collection, processing and storage of these biological samples and available measures. Together with detailed phenotype measurements, these biological samples provide a unique resource for epidemiological studies focused on environmental exposures, genetic and genomic determinants and their interactions in relation to growth, health and development from fetal life onwards.