Familial Factors, Low Birth Weight, and Development of ESRD: A Nationwide Registry Study.

BACKGROUND: Previous studies have demonstrated that low birth weight (LBW) is associated with higher risk for end-stage renal disease (ESRD). However, both LBW and ESRD cluster in families. The present study investigates whether familial factors explain the association between LBW and ESRD. STUDY DESIGN: Retrospective registry-based cohort study. SETTING & PARTICIPANTS: Since 1967, the Medical Birth Registry of Norway has recorded medical data for all births in the country. Sibling data are available through the Norwegian Population Registry. Since 1980, all patients with ESRD in Norway have been registered in the Norwegian Renal Registry. Individuals registered in the Medical Birth Registry with at least 1 registered sibling were included. PREDICTOR: LBW in the participant and/or LBW in at least 1 sibling. OUTCOME: ESRD. RESULTS: Of 1,852,080 included individuals, 527 developed ESRD. Compared with individuals without LBW and with no siblings with LBW, individuals without LBW but with a sibling with LBW had an HR for ESRD of 1.20 (95% CI, 0.91-1.59), individuals with LBW but no siblings with LBW had an HR of 1.59 (95% CI, 1.18-2.14), and individuals with LBW and a sibling with LBW had an HR of 1.78 (95% CI, 1.26-2.53). Similar results were observed for individuals who were small for gestational age (SGA). Separate analyses for the association of age 18 to 42 years and noncongenital ESRD showed stronger associations for SGA than for LBW, and the associations were not statistically significant for age 18 to 42 years for LBW. LIMITATIONS: Follow-up only until 42 years of age. CONCLUSIONS: LBW and SGA are associated with higher risk for ESRD during the first 40 years of life, and the associations were not explained by familial factors. Our results support the hypothesis that impaired intrauterine nephron development may be a causal risk factor for progressive kidney disease.

Low Birth Weight and Risk of Progression to End Stage Renal Disease in IgA Nephropathy--A Retrospective Registry-Based Cohort Study.

BACKGROUND: Low Birth Weight (LBW) is a surrogate for fetal undernutrition and is associated with impaired nephron development in utero. In this study, we investigate whether having been born LBW and/or small for gestational age (SGA) predict progression to ESRD in IgA nephropathy (IgAN) patients. STUDY DESIGN: Retrospective registry-based cohort study. SETTINGS & PARTICIPANTS: The Medical Birth Registry has recorded all births since 1967 and the Norwegian Renal Registry has recorded all patients with ESRD since 1980. Based on data from the Norwegian Kidney Biopsy Registry we included all patients diagnosed with IgAN in Norway from 1988-2013. These registries were linked and we analysed risk of progression to ESRD associated with LBW (defined as birth weight less than the 10th percentile) and/or SGA (defined as birth weight less than the 10th percentile for gestational week) by Cox regression statistics. RESULTS: We included 471 patients, of whom 74 developed ESRD. As compared to patients without LBW, patients with LBW had a hazard ratio (HR) of 2.0 (95% confidence interval 1.1-3.7) for the total cohort, 2.2 (1.1-4.4) for males and 1.3 (0.30-5.8) for females. Corresponding HRs for SGA were 2.2 (1.1-4.2), 2.7 (1.4-5.5) and 0.8 (0.10-5.9). Further analyses showed that as compared to patients with neither LBW nor SGA, patients with either SGA or LBW did not have significantly increased risks (HRs of 1.3-1.4) but patients who were both LBW and SGA had an increased risk (HR 3.2 (1.5-6.8). LIMITATION: Mean duration of follow-up only 10 years and maximum age only 46 years. CONCLUSION: Among IgAN patients, LBW and/or SGA was associated with increased risk for progression to ESRD, the association was stronger in males.