Use of hierarchical models to analyze European trends in congenital anomaly prevalence.
BACKGROUND
Surveillance of congenital anomalies is important to identify potential teratogens. Despite known associations between different anomalies, current surveillance methods examine trends within each subgroup separately. We aimed to evaluate whether hierarchical statistical methods that combine information from several subgroups simultaneously would enhance current surveillance methods using data collected by EUROCAT, a European network of population-based congenital anomaly registries.


METHODS
Ten-year trends (2003 to 2012) in 18 EUROCAT registries over 11 countries were analyzed for the following groups of anomalies: neural tube defects, congenital heart defects, digestive system, and chromosomal anomalies. Hierarchical Poisson regression models that combined related subgroups together according to EUROCAT's hierarchy of subgroup coding were applied. Results from hierarchical models were compared with those from Poisson models that consider each congenital anomaly separately.


RESULTS
Hierarchical models gave similar results as those obtained when considering each anomaly subgroup in a separate analysis. Hierarchical models that included only around three subgroups showed poor convergence and were generally found to be over-parameterized. Larger sets of anomaly subgroups were found to be too heterogeneous to group together in this way.


CONCLUSIONS
There were no substantial differences between independent analyses of each subgroup and hierarchical models when using the EUROCAT anomaly subgroups. Considering each anomaly separately, therefore, remains an appropriate method for the detection of potential changes in prevalence by surveillance systems. Hierarchical models do, however, remain an interesting alternative method of analysis when considering the risks of specific exposures in relation to the prevalence of congenital anomalies, which could be investigated in other studies. Birth Defects Research (Part A) 106:480-10, 2016. © 2016 Wiley Periodicals, Inc.
Wolfson Institute of Preventive Medicine, Queen Mary University of London, United Kingdom.
Alana
A
Cavadino
Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, United Kingdom.|Farr Institute of Health Informatics Research, University College London, United Kingdom.|Catholic University of Murcia (UCAM), Spain.
David
D
Prieto-Merino
Service de Genetique Medicale Maternite, CHUV, Lausanne, Switzerland.
Marie-Claude
MC
Addor
Public Health Division of Gipuzkoa, Instituto BIO-Donostia Basque Government CIBER Epidemiología y Salud Pública - CIBERESP, San Sebatian, Spain.
Larraitz
L
Arriola
CNR Institute of Clinical Physiology and Tuscany Registry of Congenital Defects, "Gabriele Monasterio" Foundation, Pisa, Italy.
Fabrizio
F
Bianchi
Department of Health Sciences, University of Leicester, Leicester, United Kingdom.
Elizabeth
E
Draper
Paediatric Department, Hospital Lillebaelt-Kolding, Denmark.
Ester
E
Garne
Institute of Nursing and Health Research, Ulster University, Newtownabbey, United Kingdom.
Ruth
R
Greenlees
Medical University of Graz, Austria.
Martin
M
Haeusler
Obstetrical, Perinatal and Pediatric Epidemiology Research Team, Center for Biostatistics and Epidemiology, INSERM U1153, Maternité de Port-Royal, Paris, France.
Babak
B
Khoshnood
National Perinatal Epidemiology Unit, Nuffield Department of Population Health, University of Oxford, United Kingdom.
Jenny
J
Kurinczuk
Health Service Executive, Dublin, Ireland.
Bob
B
McDonnell
Provincial Institute for Hygiene, Antwerp, Belgium.
Vera
V
Nelen
Department of Public Health, Health Service Executive - South, Ireland.
Mary
M
O'Mahony
Medical Genetics Unit of CHU Sud Réunion, Ile de la Reunion, France.
Hanitra
H
Randrianaivo
Institute of Health & Society, Newcastle University, Newcastle, United Kingdom.
Judith
J
Rankin
Malformation Monitoring Centre Saxony-Anhalt, Medical Faculty Otto-von-Guericke University, Magdeburg, Germany.
Anke
A
Rissmann
Public Health Wales, Swansea, United Kingdom.
David
D
Tucker
Center for Human Genetics, Institut de Recherche Scientifique en Pathologie et en Génétique, Charleroi, Belgium.
Christine
C
Verellen-Dumoulin
University of Groningen, University Medical Center Groningen, Department of Genetics, Groningen, Netherlands.
Hermien
H
de Walle
University Hospitals Southampton, Faculty of Medicine and Wessex Clinical Genetics Service, Princess Anne Hospital, Southampton, United Kingdom.
Diana
D
Wellesley
Wolfson Institute of Preventive Medicine, Queen Mary University of London, United Kingdom.
Joan K
JK
Morris
D000013:Congenital Abnormalities / Q000453:epidemiology*; D005060:Europe / Q000453:epidemiology; D005260:Female; D006801:Humans; D008297:Male; D008954:Models, Biological; D015995:Prevalence; D012042:Registries
congenital anomalies; hierarchical models; prevalence; trends