Registers of the Swedish total population and their use in medical research

The primary aim of the Swedish national population registration system is to obtain data that (1) reflect the composition, relationship and identities of the Swedish population and (2) can be used as the basis for correct decisions and measures by government and other regulatory authorities. For this purpose, Sweden has established two population registers: (1) The Population Register, maintained by the Swedish National Tax Agency ("Folkbokforingsregistret"); and (2) The Total Population Register (TPR) maintained by the government agency Statistics Sweden ("Registret over totalbefolkningen"). The registers contain data on life events including birth, death, name change, marital status, family relationships and migration within Sweden as well as to and from other countries. Updates are transmitted daily from the Tax Agency to the TPR. In this paper we describe the two population registers and analyse their strengths and weaknesses. Virtually 100 % of births and deaths, 95 % of immigrations and 91 % of emigrations are reported to the Population Registers within 30 days and with a higher proportion over time. The over-coverage of the TPR, which is primarily due to underreported emigration data, has been estimated at up to 0.5 % of the Swedish population. Through the personal identity number, assigned to all residents staying at least 1 year in Sweden, data from the TPR can be used for medical research purposes, including family design studies since each individual can be linked to his or her parents, siblings and offspring. The TPR also allows for identification of general population controls, participants in cohort studies, as well as calculation of follow-up time.NonePublishe

Perinatal Risk Factors for Diabetes in Later Life

OBJECTIVE—Low birth weight is consistently associated with an increased risk of type 2 diabetes in adulthood, but the individual contributions from poor fetal growth and preterm birth are not known. We therefore investigated the significance of these two factors separately

Risk of Hypertension Among Young Adults Who Were Born Preterm: A Swedish National Study of 636,000 Births

Previous studies have reported an association between preterm birth and elevated blood pressure in adolescence and young adulthood. These studies were based on single-day blood pressure measurements and had limited ability to estimate risk of hypertension measured over a longer period and across the full range of gestational ages. The authors conducted a national cohort study of all infants born in Sweden from 1973 through 1979 (n = 636,552), including 28,220 born preterm (<37 weeks), followed to ages 25.5–37.0 years to determine whether individuals born preterm were more likely to be prescribed antihypertensive medications in 2005–2009 than those born full term. Antihypertensive medication data were obtained from all outpatient and inpatient pharmacies throughout Sweden. Young adults who were born preterm had an increased relative rate of antihypertensive medication prescription that increased monotonically by earlier gestational age and that was independent of fetal growth. The adjusted odds ratio for ≥1 antihypertensive medications/year ranged from 1.25 (95% confidence interval: 1.12, 1.39) for those born near term (35–36 weeks) to 2.51 (95% confidence interval: 1.11, 5.68) for those born extremely preterm (23–27 weeks) relative to those born full term. These findings suggest that preterm birth is strongly associated with hypertension in young adulthood, including an increased risk among those born near term

EPICE cohort: Two year neurodevelopmental outcomes after very preterm birth.

Objective: to determine whether the variation in neurodevelopmental disability rates between populations persists after adjustment for demographic, maternal and infant characteristics for an international very preterm birth (VPT) cohort using a standardised approach to neurodevelopmental assessment at two years of age. Design: Prospective standardised cohort study. Setting: 15 regions in 10 European countries. Patients: VPT births: 22+0-31+6 weeks of gestation. Data collection: standardised data collection tools relating to pregnancy, birth and neonatal care and developmental outcomes at 2 years corrected age using a validated parent completed questionnaire. Main outcome measures: Crude and standardised prevalence ratios calculated to compare rates of moderate to severe neurodevelopmental impairment between regions grouped by country using fixed effects models. Results: Parent reported rates of moderate or severe neurodevelopmental impairment for the cohort were: 17.3% (ranging 10.2% to 26.1% between regions grouped by country) with crude standardised prevalence ratios ranging from 0.60 to 1.53. Adjustment for population, maternal and infant factors resulted in a small reduction in the overall variation (ranging from 0.65 to 1.30). Conclusion: There is wide variation in the rates of moderate to severe neurodevelopmental impairment for VPT cohorts across Europe, much of which persists following adjustment for known population, maternal and infant factors. Further work is needed to investigate whether other factors including quality of care and evidence based practice have an effect on neurodevelopmental outcomes for these chil

EPICE cohort: two-year neurodevelopmental outcomes after very preterm birth

Objective: To determine whether the variation in neurodevelopmental disability rates between populations persists after adjustment for demographic, maternal and infant characteristics for an international very preterm (VPT) birth cohort using a standardised approach to neurodevelopmental assessment at 2 years of age. Design: Prospective standardised cohort study. Setting: 15 regions in 10 European countries. Patients: VPT births: 22+0-31+6 weeks of gestation. Data collection: Standardised data collection tools relating to pregnancy, birth and neonatal care and developmental outcomes at 2 years corrected age using a validated parent completed questionnaire. Main outcome measures: Crude and standardised prevalence ratios calculated to compare rates of moderate to severe neurodevelopmental impairment between regions grouped by country using fixed effects models. Results: Parent reported rates of moderate or severe neurodevelopmental impairment for the cohort were: 17.3% (ranging 10.2%-26.1% between regions grouped by country) with crude standardised prevalence ratios ranging from 0.60 to 1.53. Adjustment for population, maternal and infant factors resulted in a small reduction in the overall variation (ranging from 0.65 to 1.30). Conclusion: There is wide variation in the rates of moderate to severe neurodevelopmental impairment for VPT cohorts across Europe, much of which persists following adjustment for known population, maternal and infant factors. Further work is needed to investigate whether other factors including quality of care and evidence-based practice have an effect on neurodevelopmental outcomes for these children

Preterm arteries in childhood : Dimensions, intima-media thickness, and elasticity of the aorta, coronaries, and carotids in 6-y-old children born extremely preterm

Background:Preterm birth increases risk for adult cardiovascular disease. We hypothesized that arteries in 6-y-old children born preterm are narrower, with thicker intima-media and stiffer than in peers born at term.Methods:Children born extremely preterm (EXP, n = 176, birthweights: 348-1,161 g) and at term (CTRL, n = 174, birthweights: 2,430-4,315 g) were included. Using ultrasonography, we determined diameters of the coronaries (CA), common carotid arteries (CCA) and aorta, the carotid intima media thickness (cIMT), and the stiffness index of the CCA and aorta.Results:Arteries were 5-10% narrower in EXP than in CTRL (P < 0.005) but after adjustment for body surface area, diameter differences diminished or disappeared. EXP-children born small for gestational age exhibited similar arterial dimensions as those born appropriate for date. The cIMT was 0.38 (SD = 0.04) mm and did not differ between groups. Carotid but not aortic stiffness was lower in EXP than in CTRL.Conclusion:In 6-y-old children born extremely preterm, conduit arteries are of similar or smaller size than in controls born at term, and they have no signs of accelerated intima media thickening or arterial stiffening. While these findings are reassuring for these children and their families, the causal pathways from preterm birth to adult cardiovascular disease remain unknown

Supplementary Material for: Patent Ductus Arteriosus Treatment in Very Preterm Infants: A European Population-Based Cohort Study (EPICE) on Variation and Outcomes

<p><b><i>Background:</i></b> Spontaneous closure of patent ductus arteriosus (PDA) occurs frequently in very preterm infants and despite the lack of evidence for treatment benefits, treatment for PDA is common in neonatal medicine. <b><i>Objectives:</i></b> The aim of this work was to study regional variations in PDA treatment in very preterm infants (≤31 weeks of gestation), its relation to differences in perinatal characteristics, and associations with bronchopulmonary dysplasia (BPD) and survival without major neonatal morbidity. <b><i>Methods:</i></b> This was a population-based cohort study in 19 regions in 11 European countries conducted during 2011 and 2012. A total of 6,896 infants with data on PDA treatment were included. The differences in infant characteristics were studied across regions using a propensity score derived from perinatal risk factors for PDA treatment. The primary outcomes were a composite of BPD or death before 36 weeks postmenstrual age, or survival without major neonatal morbidity. <b><i>Results:</i></b> The proportion of PDA treatment varied from 10 to 39% between regions (<i>p</i> < 0.001), and this difference could not be explained by differences in perinatal characteristics. The regions were categorized according to a low (<15%, <i>n</i> = 6), medium (15-25%, <i>n</i> = 9), or high (>25%, <i>n</i> = 4) proportion of PDA treatment. Infants treated for PDA, compared to those not treated, were at higher risk of BPD or death in all regions, with an overall propensity score adjusted risk ratio of 1.33 (95% confidence interval 1.18-1.51). Survival without major neonatal morbidity was not related to PDA treatment. <b><i>Conclusions:</i></b> PDA treatment varies largely across Europe without associated variations in perinatal characteristics or neonatal outcomes. This finding calls for more uniform guidance for PDA diagnosis and treatment in very preterm infants.</p