title: A case-crossover study of infectious diseases and new diagnosis of type 1 diabetes.
abstract: BACKGROUND
  Infectious diseases have been associated with increased risk of type 1 diabetes (T1D). The objective of this case-crossover was to quantify the role of infectious diseases as triggers for T1D, 1 and 2 yr preceding disease diagnosis.
  
  
  METHODS
  All children aged 2-18 yr diagnosed with T1D between 2004 and 2009 among a two million member Israeli healthcare organization were identified (n = 368). For each patient, visits to physicians with symptomatic infectious diseases during 1 and 2 yr before T1D diagnosis were collected and compared. A similar analysis was conducted in a population of non-diabetic members matched on exact date of birth, sex and socioeconomic status (n = 307).
  
  
  RESULTS
  The rate of systemic viral infections was significantly higher in the year before T1D onset, as compared to the prior year [27 vs. 7%, respectively, odds ratio (OR) = 4.7, 95% confidence intervals (CI): 2.9-8.2]. This difference was most significant among patients diagnosed with T1D at the age of 2 to 6 (5 vs. 46%, respectively, OR = 27.0, 95% CI: 4.5-1105.4). Among non-T1D patients of the same age group, no difference was found in the proportion of patients with viral diseases 1 and 2 yr prior to T1D diagnosis (44 vs. 49%, respectively, OR = 0.8, 95% CI: 0.4-1.6). This unique association was limited only to viral diseases and to patients diagnosed with T1D at young age.
  
  
  CONCLUSIONS
  Our results indicate that T1D occurring in toddlers is characterized with a relatively low incidence of viral disease 2 yr prior to diagnosis and a much higher incidence in the subsequent year.
authors: Medical Division, Maccabi Healthcare Services, Tel Aviv, 68125, Israel.
authors: Aushrat
authors: A
authors: Shoshan
authors: Tal
authors: T
authors: Sella
authors: Tamar
authors: T
authors: Shohat
authors: Iris
authors: I
authors: Goren
authors: Varda
authors: V
authors: Shalev
authors: Gabriel
authors: G
authors: Chodick
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D003141:Communicable Diseases / Q000150:complications*; D018592:Cross-Over Studies; D003922:Diabetes Mellitus, Type 1 / Q000453:epidemiology / Q000209:etiology*; D005260:Female; D006801:Humans; D015994:Incidence; D007557:Israel / Q000453:epidemiology; D008297:Male; D014777:Virus Diseases / Q000150:complications