title: Seasonal variation in month of diagnosis in children with type 1 diabetes registered in 23 European centers during 1989-2008: little short-term influence of sunshine hours or average temperature.
abstract: BACKGROUND
  The month of diagnosis in childhood type 1 diabetes shows seasonal variation.
  
  
  OBJECTIVE
  We describe the pattern and investigate if year-to-year irregularities are associated with meteorological factors using data from 50 000 children diagnosed under the age of 15 yr in 23 population-based European registries during 1989-2008.
  
  
  METHODS
  Tests for seasonal variation in monthly counts aggregated over the 20 yr period were performed. Time series regression was used to investigate if sunshine hour and average temperature data were predictive of the 240 monthly diagnosis counts after taking account of seasonality and long term trends.
  
  
  RESULTS
  Significant sinusoidal pattern was evident in all but two small centers with peaks in November to February and relative amplitudes ranging from ± 11 to ± 38% (median ± 17%). However, most centers showed significant departures from a sinusoidal pattern. Pooling results over centers, there was significant seasonal variation in each age-group at diagnosis, with least seasonal variation in those under 5 yr. Boys showed greater seasonal variation than girls, particularly those aged 10-14 yr. There were no differences in seasonal pattern between four 5-yr sub-periods. Departures from the sinusoidal trend in monthly diagnoses in the period were significantly associated with deviations from the norm in average temperature (0.8% reduction in diagnoses per 1 °C excess) but not with sunshine hours.
  
  
  CONCLUSIONS
  Seasonality was consistently apparent throughout the period in all age-groups and both sexes, but girls and the under 5 s showed less marked variation. Neither sunshine hour nor average temperature data contributed in any substantial way to explaining departures from the sinusoidal pattern.
authors.affiliation: Centre of Excellence for Public Health Northern Ireland, Queen's University Belfast, Belfast, UK.
authors.forename: C C
authors.initials: CC
authors.lastname: Patterson
authors.affiliation: Department of Paediatrics, Pécs University, Pecs, Hungary.
authors.forename: E
authors.initials: E
authors.lastname: Gyürüs
authors.affiliation: Institute for Biometrics and Epidemiology, German Diabetes Center, Leibniz Institute for Diabetes Research at Heinrich Heine University, Düsseldorf, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Rosenbauer
authors.affiliation: Department of Pediatrics, 2nd Faculty of Medicine, Charles University in Prague and University Hospital Motol, Prague, Czech Republic.
authors.forename: O
authors.initials: O
authors.lastname: Cinek
authors.affiliation: Pediatric Endocrinology & Diabetes, University Children's Hospital, Tübingen, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Neu
authors.affiliation: Department of Pediatric and Adolescent Medicine, Medical University of Vienna, Vienna, Austria.
authors.forename: E
authors.initials: E
authors.lastname: Schober
authors.affiliation: Leeds Institute of Genetics, Health and Therapeutics, University of Leeds, Leeds, UK.
authors.forename: R C
authors.initials: RC
authors.lastname: Parslow
authors.affiliation: Department of Pediatrics, Ullevål University Hospital, Oslo, Norway.
authors.forename: G
authors.initials: G
authors.lastname: Joner
authors.affiliation: Department of Paediatrics, Herlev University Hospital, Copenhagen, Denmark.
authors.forename: J
authors.initials: J
authors.lastname: Svensson
authors.affiliation: Public Health Agency, Department of Health, Government of Catalonia, Barcelona, Spain.
authors.forename: C
authors.initials: C
authors.lastname: Castell
authors.affiliation: School of Clinical Sciences, University of Bristol, Bristol, UK.
authors.forename: P J
authors.initials: PJ
authors.lastname: Bingley
authors.affiliation: Department of Endocrinology and Diabetology, University Children's Hospital, Zurich, Switzerland.
authors.forename: E
authors.initials: E
authors.lastname: Schoenle
authors.affiliation: Department of Pediatrics, Endocrinology and Diabetes, Medical University of Silesia, Katowice, Poland.
authors.forename: P
authors.initials: P
authors.lastname: Jarosz-Chobot
authors.affiliation: Institute of Endocrinology, Lithuanian University of Health Science, Kaunas, Lithuania.
authors.forename: B
authors.initials: B
authors.lastname: Urbonaité
authors.affiliation: Department for Epidemiology and Health Care Research, Technical University of Dresden, Dresden, Germany.
authors.forename: U
authors.initials: U
authors.lastname: Rothe
authors.affiliation: Department of Pediatrics, University Children's Hospital, Ljubljana, Slovenia.
authors.forename: C
authors.initials: C
authors.lastname: Kržišnik
authors.affiliation: Nutrition and Metabolic Diseases Clinic, N Paulescu Institute of Diabetes and Metabolic Diseases, Bucharest, Romania.
authors.forename: C
authors.initials: C
authors.lastname: Ionescu-Tirgoviste
authors.affiliation: Diabetes Research Center, Brussels Free University, Vrije Universiteit Brussel, Brussels, Belgium.
authors.forename: I
authors.initials: I
authors.lastname: Weets
authors.affiliation: Department of Endocrinology and Genetics, University Children's Hospital, Skopje, Macedonia.
authors.forename: M
authors.initials: M
authors.lastname: Kocova
authors.affiliation: Department of Paediatrics, University Hospital Sestre Milosrdnice, Zagreb, Croatia.
authors.forename: G
authors.initials: G
authors.lastname: Stipancic
authors.affiliation: Department of Endocrinology and Diabetes, University Children's Hospital, Podgorica, Montenegro.
authors.forename: M
authors.initials: M
authors.lastname: Samardzic
authors.affiliation: Department of Paediatric Diabetes and Endocrinology, Centre Hospitalier de Luxembourg, Luxembourg.
authors.forename: C E
authors.initials: CE
authors.lastname: de Beaufort
authors.affiliation: Odense Patient data Exploratory Network, University of Southern Denmark, Odense, Denmark.
authors.forename: A
authors.initials: A
authors.lastname: Green
authors.affiliation: Department of Paediatrics, Pécs University, Pecs, Hungary.
authors.forename: G
authors.initials: G
authors.lastname: Soltész
authors.affiliation: Department of Clinical Science, University of Umeå, Umeå, Sweden.
authors.forename: G G
authors.initials: GG
authors.lastname: Dahlquist
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D003922:Diabetes Mellitus, Type 1 / Q000175:diagnosis*; D005060:Europe; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D017440:Photoperiod; D012042:Registries; D012621:Seasons; D013696:Temperature
keywords: epidemiology; seasonality; sunshine; temperature; temporal change; type 1 diabetes mellitus