Associations of Prematurity and Low Birth Weight With Blood Pressure and Kidney Function in Middle-aged Participants of the Brazilian Longitudinal Study of Adult Health – ELSA-Brasil

doi:10.21203/rs.3.rs-660337/v1

Background

Based on the Developmental Origins of Health and Disease, adverse intrauterine environment – reflected by low birth weight (LBW) and prematurity – may induce fetal programming that favors kidney dysfunction in adulthood. We examined the association of LBW and prematurity with blood pressure (BP) and kidney function markers in non-diabetic middle-aged adults without kidney disease from the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil).

Methods

A cross-sectional analysis of 768 subjects aged 35-54 years was conducted. Comparisons were performed according to birth weight: LBW (<2.5 kg) or normal birth weight (NBW) (2.5-4.0 kg). Associations of LBW and prematurity with BP levels and kidney function markers (glomerular filtration rate - eGFR, albumin-creatinine ratio - ACR and serum cystatin C) were tested by multiple linear regression using adjustments based on Directed Acyclic Graphs. Propensity score matching was applied to control imbalances.

Results

Mean age of participants was 45.5 ± 4.6 years and 56.8% were female; 64 (8.3%) participants reported LBW and 39 (5.0%) prematurity. The LBW group had higher systolic (p = 0.015) and diastolic BP (p = 0.014) and ACR values (p = 0.031) and lower eGFR (p = 0.015) than the NBW group, but no group difference for serum cystatin C was found. The preterm group had higher mean levels of systolic and diastolic BP, but no difference in kidney function markers was evident. In a regression model adjusted for sex, skin color and family history of hypertension, both systolic and diastolic BP levels were associated with LBW, but this association disappeared after adding prematurity, which remained associated with BP (p = 0.017). Having applied propensity score matching, LBW was associated with ACR values (p=0.003), but not with eGFR or BP levels.

Conclusion

The study findings of independent associations of prematurity with higher BP levels, and of LBW with markers of kidney function, in adulthood support that early life events predict risk for hypertension and kidney dysfunction in adulthood. The study design precluded the inferring of causality, and prospective studies are needed to further investigate the hypothesis raised.

Urology & Nephrology

low birth weight

prematurity

reduced kidney function

blood pressure

Based on the Developmental Origins of Health and Disease (DOHaD) theory, early life events can increase the risk of noncommunicable diseases in adulthood¹. Nutrition-related and other stressors during pregnancy may result in low birth weight (LBW), considered a proxy of an adverse intrauterine environment² and commonly the result of intrauterine growth restriction or prematurity³. Given the short- and long-term adverse outcomes in LBW neonates, this condition remains a major public health concern. The World Health Organization (WHO) estimates that LBW occurs in 15–20% of all births, with rates varying widely according to country income level⁴. Compelling evidence has indicated that LBW may predict cardiometabolic and renal disorders^5,6.

Perinatal distress has been associated with blood pressure level elevation in adulthood⁷. Underlying mechanisms for the association of early life events with blood pressure elevation have been proposed in animal and human models^8,9. Changes in RAS gene expression, activity of the angiotensin-converting enzyme and sympathetic nervous system, may contribute to development of hypertension in adult life^10–12. Sustained increased blood pressure levels with gradual glomerular damage may precipitate chronic renal failure.

Nephrogenesis begins at early stages of embryo life with an increase in glomeruli number in the last weeks of gestation¹³. Insults during intrauterine life (undernutrition, toxic exposures and/or placental abnormalities) ¹⁴ can negatively impact renal functional reserve. These adverse events can induce fetal programming with resultant reduction in nephron formation, hypertrophy of the remaining nephrons, leading to adaptive hyperfiltration and increased risk of kidney dysfunction later in life^15,16. An early sign of hypertension-dependent glomerular damage is urinary protein loss¹⁷.

Issues regarding whether LBW adults born at full-term or prematurely are prone to exhibit different long-term consequences, and whether these changes can be detected early in the natural history of hypertension and chronic kidney disease, remain understudied.

The Brazilian Longitudinal Study of Adult Health (ELSA-Brasil) is a large cohort that provides an opportunity to investigate the relationship of exposures with several outcomes in adulthood^18,19. In particular, this allows the testing of associations of early life events with blood pressure levels and renal function markers in adults without overt kidney diseases. We examined the association of LBW and prematurity with blood pressure levels and kidney function markers in middle-aged non-diabetic participants of ELSA-Brasil without kidney disease.

Study design and population

A cross-sectional analysis was carried out of the baseline cohort from the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil), a multicenter cohort study aimed at investigating biological, behavioral, environmental, occupational, psychological, and social factors related to incidence and progression of diabetes and cardiovascular disease¹⁹. Methodological details have been reported elsewhere^18,19. Briefly, from August 2008 to December 2010, ELSA-Brasil included employees aged 35–74 years working in universities and research institutions located in the Northeast, Southeast and South regions of Brazil. The current study involved a random sample of 998 non-diabetic individuals aged 35–54 years, drawn from 5061 participants at the São Paulo center of the ELSA-Brasil for whom information on biomarkers of inflammation and serum Cystatin C (sCys C) was available²⁰. The study was approved by the local Ethics Committee and informed consent was obtained from all participants.

Eligibility criteria

Of the initial 998 participants, 17 with newly diagnosed diabetes and 16 with low estimated glomerular filtration rate (eGFR < 60 mL/min/1.73m²) were excluded, as were 8 underweight individuals and 50 participants born with macrosomia. Considering thyroid and liver dysfunctions can affect plasma sCys C levels, participants with TSH < 0.1 or ≥ 10.0 µUI/mL (n = 18) and with ALT/AST levels three-fold the normal range (n = 2) were excluded. Participants with missing data regarding exposure (birth weight) or outcomes (sCys C, eGFR and ACR) were also excluded (n = 119), as shown in Fig. 1. A final total of 768 participants were thus included in the present study.

Clinical and laboratory data

Interview and anthropometric data were collected by trained personnel using standardized questionnaires²¹. Prematurity (yes or no) and birth weight were self-reported. Participants were asked to recall their weight at birth and the variable was classified into “< 2.5 kg”, “2.5-4.0 kg”, “> 4.0 kg” or “unknown”. All participants were asked to provide their specific birth weight and to recall their body weight at 20 years of age.

Sociodemographic and health factors of interest for this study were: age (years), sex (male or female), self-reported skin color (black, white, brown, yellow and indigenous), parental history of diabetes and hypertension (yes or no) and educational levels of the participant and their mother. For the purpose of the present study, skin colors were grouped into white and non-white categories.

Blood pressure was measured using an Omron HEM 705CPINT device (Omron Co, Kyoto, Japan) after a 5-minute rest in a sitting position. Three measurements were taken at 1-min intervals and mean values calculated. Body mass index (BMI) was calculated as weight in kilograms divided by height in meters squared. After overnight fasting, blood and urine samples were obtained and participants then underwent a 2-hour 75 g oral glucose tolerance test. Aliquots of biological samples were frozen at -80^oC for further analyses^22,23.

Fasting and 2-hour post-load plasma glucose were measured using the hexokinase method (ADVIA Chemistry; Siemens, Deerfield, Illinois, USA) and glycated hemoglobin by high-pressure liquid chromatography (HPLC) (Bio-Rad Laboratories, Hercules, California, USA), according to the National Glycohemoglobin Standardization Program (NGSP) certified method. Glomerular filtration rate was estimated using the equations proposed by the Chronic Kidney Disease Epidemiology Collaboration (eGFR CKD-EPI)²⁴. Albuminuria was determined in a 12-h overnight sample by nephelometry and was expressed as albumin-to-creatinine ratio (ACR). Serum cystatin C was measured using a human cystatin C ELISA kit (Elabscience Biotechnology, Houston, Texas, USA). Intra-assay and inter-assay coefficient of variability ranges were 5.05–5.38% and 3.29–6.48%, respectively.

Definitions

Prematurity was defined by an affirmative answer to the question: “Were you a premature baby, that is, were you born earlier than expected?”. Birth weight was classified into 3 categories: low birth weight (< 2.5 kg), normal birth weight (2.5–4.0 kg) and macrosomia (> 4.0 kg). Outcomes were blood pressure (BP) levels, eGFR, ACR and sCys C and were analyzed as continuous variables.

Hypertension was diagnosed when systolic or diastolic blood pressure levels were ≥ 140 or 90 mmHg, respectively, or when individual was in use of antihypertensive drugs. Kidney function was considered altered for eGFR < 60 mL/min/1.73m² or urinary albumin excretion > 1,000 mg/g creatinine, according to KDIGO 2012²⁵. Normal ranges of sCys C were 0.64–0.84 mg/L for men and 0.57–0.74 mg/L for women²⁶.

Diabetes diagnosis was established when fasting plasma glucose ≥ 126 mg/dL or 2-hour post 75-g glucose load > 200 mg/dL or glycated hemoglobin ≥ 6.5%. Other variables were categorized as following: prediabetes (yes or no) defined as fasting plasma glucose between 100–125 mg/dL or 2-hour post 75-g glucose load between 140–199 mg/dL or glycated hemoglobin 5.7–6.4%; nutritional status was stratified by BMI into underweight (< 18.5 kg/m²), normal weight (18.5–24.9 kg/m²), overweight (25–29.9 kg/m²) and obese (> 30 kg/m²). Insulin sensitivity was assessed using the Homeostasis Model Assessment of Insulin Resistance (HOMA-IR) and considered a continuous variable.

Statistical analysis

Continuous variables with normal distribution were expressed as mean ± standard deviation (SD) and compared using Student´s t-test. Non-normal distributed parametric variables were expressed as median and interquartile range and compared using the Wilcoxon rank test. Categorical variables were expressed as absolute and relative frequencies and compared using the chi-squared test.

Associations of LBW (exposure) with outcomes (blood pressure levels and kidney function parameters) were initially analyzed by simple linear regression. Direct Acyclic Graphs (DAG) were used to build theoretical models to analyze independent associations of exposure with outcomes in multiple linear regression analyses. The DAG is a causal diagram which allows the input of scientific evidence regarding the relationships among variables in graphics software to reach the ideal set of covariables (minimum sufficient adjustment) for the model to prevent bias and overadjustments^27,28. The figures were created using DAGitty software, version 3.0 (www.dagitty.net), included in the Supplementary material (Figure S1 – Panels A and B).

Based on DAGs, linear regression models for the association of LBW with blood pressure levels were adjusted for race/skin color, sex, parental history of hypertension, and prematurity. Linear regression models for the associations of LBW with kidney function parameters (eGFR, ACR and sCys C) were adjusted for skin color and prematurity.

Considering the contrasting sample sizes of the groups with normal and LBW, as well as possible selection bias due to the observational nature of the study, propensity score matching was employed to create more comparable groups^29,30. The nearest neighbor-matching algorithm, within a caliper of 0.1 SD of logit function of propensity score was used. Firstly, to apply the propensity score matching, a multiple logistic regression model was used, adjusted for DAG-based covariates (blood pressure was adjusted for skin color, sex, parental history of hypertension and prematurity; while kidney function markers were adjusted for skin color and prematurity), and the probability of each participant being LBW versus normal birth weight was estimated. Balance between the groups was assessed by comparing each covariate. When standardized mean difference lay in the − 0.1 to 0.1 range, groups were considered balanced. This matching was able to reduce all covariate imbalance in the sample. Using the matched sample, multiple linear regression analyses were then performed to test associations of LBW with blood pressure and kidney function markers (outcomes) adjusted for the same DAG-based covariates. Tests were performed using “MatchIt”, “rbounds”, “Matching”, “twang” and “survey” packages in the R statistical environment.

Additionally, sensitivity analyses were performed by selecting the participants with self-reported preterm birth (prematurity). Also, when blood pressure levels were outcomes, sensitivity analyses were carried out excluding participants who reported use of antihypertensive agents (Supplementary Table S1). Since similar results were obtained in both analyses, preterm and hypertensive participants were retained for subsequent analysis.

All analyses were performed using R Project for Statistical Computing (R version 3.5.2) and statistical significance was set at a p-value of 0.05.

In the sample of 768 participants, mean age was 45.5 ± 4.6 years, 56.8% were female, and 60% reported white skin color. A total of 64 (8.3%) participants reported being LBW and 39 (5.0%) born preterm. The LBW group comprised participants that were predominantly female (54.6%), white skinned (56.0%) and had mothers with low educational level (71.9%). These characteristics showed a similar pattern in the preterm subgroup (67.0% female and 61.0% white skin color).

Overall, cardiometabolic risk profile and kidney function of the total sample were within normal ranges, except for being generally overweight (mean 26.0 kg/m² ± 4.15) and having borderline fasting plasma glucose (102.0 mg/dL ± 7.5). Mean values of systolic (116.7 ± 14.7 mmHg) and diastolic (74.9 ± 10.5 mmHg) blood pressure, eGFR (89.6 ± 13.8 mL/min/1.73 m²), ACR (11.0 ± 39.0 mg/g creatinine) and sCys C (0.74 ± 0.61 mg/L) were within normal ranges.

Only 133 participants fulfilled the diagnostic criteria for hypertension. Among the hypertensive participants, 8.1 % and 14 % were receiving antihypertensive treatment in the normal and LBW groups, respectively. Hypertension rates differed between normal and LBW groups (16.2% versus 29.7%, p = 0.024).

Low birth weight participants were, on average, older than normal birth weight subjects (47.0 ± 5.5 years versus 45.3 ± 4.8 years, p = 0.027) and had higher prevalence of low educational level (6.3 versus 3.7 %, p = 0.025). Mean BMI values were lower at age 20 (21.2 ± 2.81 versus 20.7 ± 3.0 kg/m², p = 0.196) than at current age (26.2 ± 4.1 versus 26.0 ± 4.4 kg/m², p = 0.688) for both normal and LBW participants, respectively, with no difference between subgroups.

Participants with LBW had higher mean blood pressure and ACR, and lower eGFR, than individuals with normal birth weight, but there were no group differences for sCys C (Table 1).

The preterm subgroup also had significantly higher mean systolic and diastolic blood pressure levels, but no difference in kidney function markers was detected (Supplementary Table S2).

On multiple linear regression analysis, LBW was associated with blood pressure levels but this association did not persist after adjustment for prematurity, which remained associated with systolic and diastolic blood pressure (Table 2). Associations of LBW with eGFR and ACR in the fully adjusted models had borderline significance (p = 0.05) (Table 3). In a separate analysis of only preterm participants, prematurity was independently associated with both systolic and diastolic blood pressure (Supplementary Table S3).

Table 1

Main characteristics of ELSA-Brasil participants born with normal and low birth weight.
	Normal Birth Weight n = 704	Low Birth Weight n = 64	P-value
Age (years)	45.4 (4.8)	46.9 (5.5)	0.027
Body mass index at age 20 (kg/m²)	21.2 (2.8)	20.7 (3.0)	0.196
Body mass index (kg/m²)	26.2 (4.1)	26.0 (4.4)	0.688
Systolic blood pressure (mmHg)	116.3 (14.6)	121.0 (14.8)	0.015
Diastolic blood pressure (mmHg)	74.6 (10.5)	77.6 (10.8)	0.040
Hypertension n (%)	114 (16.2)	19 (29.7)	0.024
Antihypertensive treatment n (%)	57 (8.1)	9 (14)	0.162
LDL-cholesterol (mg/dL)	128.3 (32.6)	132.6 (32.1)	0.314
HDL-cholesterol (mg/dL)	55.2 (13.2)	58.2 (14.0)	0.114
Triglycerides (mg/dL)	127.7 (76.3)	124.1 (58.5)	0.646
Fasting plasma glucose (mg/dL)	101.9 (8.0)	102.2 (7.9)	0.792
HOMA-IR*	2.32 (1.65–3.38)	2.52 (1.56–3.65)	0.765
Creatinine (mg/dL)	0.92 (0.18)	0.94 (0.17)	0.254
eGFR (ml/min/1.73m²)	98.9 (16.9)	94.2 (13.9)	0.015
Albumin-creatinine ratio (mg/g)*	6.2 (4.9–7.7)	6.9 (5.2–8.9)	0.031
Cystatin C (mg/L)*	0.62 (0.37–0.91)	0.58 (0.34–0.81)	0.313
eGFR, estimated glomerular filtration rate; HOMA-IR, Homeostasis Model Assessment of Insulin Resistance

Data are expressed as mean (SD) or median (interquartile range). Student´s t test or *Wilcoxon´s test was used.

Table 2

Association of low birth weight with systolic and diastolic blood pressure.
	Β	95% CI	P-value
Systolic blood pressure
Model 1	4.34	0.85–7.83	0.015
Model 2	4.90	1.37–8.43	0.007
Model 3	2.54	− 1.52–6.61	0.220
Sex- male	10.78	8.77–12.78	< 0.001
Skin color – non-white	4.16	2.16–6.17	< 0.001
Parental history of hypertension	3.20	0.95–5.45	0.005
Prematurity	6.16	1.09–11.23	0.017
Diastolic blood pressure
Model 1	2.63	0.070–5.19	0.044
Model 2	2.93	0.34–5.52	0.026
Model 3	1.20	-1.78–4.18	0.430
Sex- male	6.62	5.15–8.09	< 0.001
Skin color – non-white	3.09	1.62–4.55	< 0.001
Parental history of hypertension	2.82	1.17–4.47	< 0.001
Prematurity	4.52	0.81–8.24	0.017
Model 1: adjusted for sex and skin color.

Model 2: adjusted for sex, skin color and parental history of hypertension.

Model 3: adjusted for sex, skin color, parental history of hypertension, and prematurity.

Table 3. Association of low birth weight with estimated glomerular filtration rate and

albumin-to-creatinine ratio.

	Β	95% CI	P-value
Estimated glomerular filtration rate
Model 1	-4.22	-6.47; - 0.001	0.049
Model 2	-4.17	-6.39 - 0.059	0.051
Albumin-to-creatinine ratio
Model 1	14.22	4.52 – 24.49	0.004
Model 2	11.08	-0.29 – 22.88	0.056

Model 1: adjusted for skin color.

Model 2: adjusted for skin color and prematurity.

Imbalance of variables

Initially, the sample had 64 participants with LBW. Propensity score matching was applied, yielding sub-samples with matched participants (normal and LBW) as follows: (a) 48 matched participants for systolic and 61 matched participants for diastolic blood pressure; (b) 44 matched participants for eGFR; and (c) 49 matched participants for ACR with the same proportion of normal and LBW participants in each sub-sample. The matching approach rendered all covariates appropriately balanced (standardized mean difference of between − 0.1 and 0.1) for further analyses. Imbalance for all variables was assessed before and after matching to compare improvement by matching (Supplementary Table S4).

Associations of LBW with blood pressure and kidney function markers after propensity score matching

The multiple linear regression model, adjusted for skin color and prematurity, showed that being born with low weight was directly associated with ACR values (ß 1.34; 95%CI 0.47 − 2.20; p = 0.003). Even when reaching adequate balance, LBW was not associated with eGFR or with systolic and diastolic blood pressure levels (Table 4).

Table 4

Estimates of associations of LBW with blood pressure and kidney function markers after propensity score matching in ELSA-Brasil participants.
	Propensity score matching
	Coefficient (ß)	95%CI	P-value
Albumin-to-creatinine ratio (mg/g)	1.34	0.47–2.20	0.003
eGFR (ml/min/1.73m²)	-0.62	-3.57–2.32	0.672
Systolic blood pressure (mmHg)	0.03	-4.70–4.77	0.989
Diastolic blood pressure (mmHg)	-1.97	-6.24–2.31	0.365
CI, confidence interval; eGFR, estimated glomerular filtration rate.

We hypothesized that being born full-term or preterm, with LBW, is associated with altered blood pressure levels and kidney function markers in adulthood, indicating an insult during intrauterine life. The findings showing both LBW and preterm participants had higher mean blood pressure levels, and that the LBW group also exhibited lower eGFR and higher ACR, than individuals with normal birth weight corroborated this hypothesis. Enhancing our analysis by propensity score matching and DAG-based adjustments on multiple linear regression boosted confidence in the associations found between early-life events and outcomes in adulthood. We suggest that a subset of individuals with LBW may be at increased risk of renal abnormalities even when routine parameters are within normal values.

Hypertension is a major cause of chronic kidney disease (CKD) and both are prevalent disorders globally^31,32. Additionally, these conditions increase the risk for cardiovascular events and deaths³³. Therefore, studies have sought to identify predictors for prevention of these diseases. There is evidence that the pathophysiological process starts in early life, congruent with the DOHaD theory^34,35. Our main results are in line with the DOHaD, which holds that insults in fetal life induce programming and that LBW is a surrogate of this condition. An interesting finding of the present study was that prematurity was associated with blood pressure levels, yet LBW was not. Previous studies have reported an association of prematurity with elevated blood pressure levels^36,37. Proposed mechanisms linking prematurity to higher blood pressure levels in adult life involve pre- and postnatal factors. Premature birth has been associated with increased vascular resistance^38,39, endothelial dysfunction⁴⁰, immature autonomic blood pressure regulation⁴¹ and high sympathetic nervous system activity¹². The extent of these abnormalities are dependent on the fetal adaptations and cardiovascular system programming in response to an adverse intrauterine environment during a critical period of development⁴². It is known that the full number of nephrons is achieved at between 32 and 36 weeks of gestation and that glomerular filtration starts during intrauterine life^13,43. Therefore, prematurity may cause morphological and functional renal changes that lead to hemodynamic disturbances and hypertension⁴⁴. Most preterm infants have accelerated postnatal growth during the first years of life⁴⁵, where this compensatory catch-up growth is commonly associated with rapid body weight gain and obesity in childhood⁴⁶. We speculate that the overweight participants in the present study have an increased risk of hypertension later in life.

Several nutritional, toxic or emotional determinants of LBW – regardless of gestational age at delivery – can impact adult kidney function^47–49, assessed by a number of parameters such as eGFR, serum creatinine, sCys C and albuminuria in clinical practice. Elevated ACR is a recognized biomarker of kidney dysfunction, even when eGFR is within normal ranges⁵⁰. In the present study, mean values of eGFR and ACR were significantly worse in the LBW group compared to the other groups.

Furthermore, having employed the propensity score matching, a strong association of LBW was found with albuminuria, but not with eGFR or sCys C. We speculate that ACR might be a useful marker for early detection of kidney dysfunction in adults born with LBW. The higher albuminuria seen in LBW individuals might have been due, in part, to fetal glomeruli morphological alterations and prenatal programming. This notion is supported by evidence demonstrating that LBW individuals have fewer nephrons⁵¹, lower glomerular volume at birth⁵², abnormal glomeruli structure with enlarged Bowman’s capsule and altered glomerular tufts^53,54, factors that, in the long-term, could result in increased glomerular permeability and albuminuria. The present sample of LBW individuals without overt nephropathy may have had glomerular hypertrophy of remaining nephrons and hyperfiltration. The current mean eGFR of this group was within the normal range, as was albuminuria, but remained significantly higher than the group with normal birth weight. Whether ACR, periodically measured, serves as a suitable marker of early kidney dysfunction in LBW individuals requires investigation by studies with the appropriate design. This is relevant considering the synergistic impact of the nephron mass on the development of hypertension favoring CKD in later life.

We elected to measure sCys C based on previous reports suggesting its greater accuracy than creatinine for detecting decreased renal function^55–57. Serum Cystatin C determination, combined with creatinine, can be used in GFR estimation (KDIGO 2012)²⁵. However, in the present sample with normal eGFR, sCys C failed to detect kidney dysfunction in LBW individuals.

This study has limitations in relation to recall bias, given that data about early life events were collected retrospectively. However, our sample was middle-aged and previous studies have shown that perinatal-related events can be accurately reported during adult life^58–60. We also used the exposure variable (LBW or prematurity) as a categorical variable, where this may have reduced the statistical power of the analysis. This variable was chosen so as to minimize information bias from participants unable to accurately remember their birth weight. The frequency of self-reported prematurity in our sample was comparable to the rate reported in the Brazilian population at large⁶¹. A strength of the present study was its methodological approach. DAG was employed to avoid overadjustments^27,28 when performing the regression analysis. However, although several covariates were incorporated into our theoretical model, including body weight at age 20, other exposures throughout the participants’ life course were unavailable. Size difference of the groups with normal birthweight and LBW was also a concern; therefore, propensity score matching was applied to reduce potential selection confounders from observational studies^29,30 and sufficiently balanced groups was achieved.

In conclusion, prematurity was found to be associated with higher blood pressure levels and LBW with albuminuria in adulthood. Considering the magnitude of the ELSA-Brasil and potentialities of its cohort^19,23, our findings are important to raise awareness of early life events and to be alert to a subset of heathy adults born with LBW at increased risk for hypertension and kidney dysfunction. Long birth cohort studies could help confirm the hypothesis raised in this study.

ACR – Albumin-creatinine ratio

ALT – Alanine aminotransferase

AST – Aspartate aminotransferase

BMI – Body mass index

BP – Blood pressure

CKD - Chronic kidney disease

CKD-EPI – Chronic kidney disease epidemiology collaboration

DAG – Direct acyclic graphs

DOHaD – Developmental origins of health and disease

eGFR – Estimated glomerular filtration rate

ELSA-Brasil – Brazilian Longitudinal Study of Adult Health

HOMA-IR – Homeostasis model assessment of insulin resistance

HPLC – High pressure liquid chromatography

KDIGO – Kidney disease: improving global outcomes

LBW – Low birth weight

NBW – Normal birth weight

NGSP – National glycohemoglobin standardization program

SD – Standard deviation

SCys C - Serum cystatin C

WHO – World Health Organization

ETHICS APPROVAL AND CONSENT TO PARTICIPATE

The study was approved by the National Commission on Ethics Research (CONEP) and by the local ethics committee, the Research Ethics Committee (CEP) under registration number 76 of the University Hospital of the University of São Paulo (HU-USP) renewed in October 7, 2007.

Informed consent was obtained from all participants in the written format during an interview with the assistance of trained personnel.

CONSENT FOR PUBLICATION

Informed consent was obtained from all participants for data publication.

AVAILABILITY OF DATA

The datasets used and analysed during the current study are available from the corresponding author on reasonable request.

COMPETING INTERESTS

Not applicable.

FUNDING

The current study was supported by grant from the São Paulo Research Foundation (Fundação de Amparo à Pesquisa do Estado de São Paulo – FAPESP – Protocol 2009/15041-9), also it was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brasil (CAPES) – (Finance Code 001). The baseline ELSA-Brasil study was supported by the Brazilian Ministry of Health (Science and Technology Department), the Brazilian Ministry of Science and Technology, and CNPq- National Research Council (# 01 06 0010.00 RS, 01 06 0212.00 BA, 01 06 0300.00 ES, 01 06 0278.00 MG, 01 06 0115.00 SP, 01 06 0071.00 RJ).

AUTHORS’ CONTRIBUTIONS

All authors have made substantial and significant contributions to this manuscript. Study design, analysis, interpretation and preparation of the manuscript: Branda, Julia; Almeida-Pititto, Bianca and Ferreira, Sandra. Acquisition of data and critical revision for the manuscript content: Lotufo, Paulo and Bensenor, Isabela.

ACKNOWLEDGMENT

The authors would like to acknowledge the participation of the 5061 individuals recruited for this study, without them this study and those based on the ELSA-Brasil cohort would not have been possible.

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No competing interests reported.

SUPPLEMENTARYMATERIAL.docx

Associations of Prematurity and Low Birth Weight With Blood Pressure and Kidney Function in Middle-aged Participants of the Brazilian Longitudinal Study of Adult Health – ELSA-Brasil

Status:

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Abstract

Figures

Introduction

Methods

Study design and population

Eligibility criteria

Clinical and laboratory data

Definitions

Statistical analysis

Results

Imbalance of variables

Associations of LBW with blood pressure and kidney function markers after propensity score matching

Discussion

Conclusion

Abbreviations

Declarations

References

Additional Declarations

Supplementary Files

Status:

Version 1