Atopy, home environment and the risk of childhood-onset type 1 diabetes: a population-based case-control study.
BACKGROUND
The marked increases in the incidence of type 1 diabetes in recent decades strongly suggest the role of environmental influences. These environmental influences remain largely unknown.


OBJECTIVE
To investigate atopy and home environment (such as children living at home, sharing a bedroom and house moves) as potential risk factors for type 1 diabetes.


METHODS
In Northern Ireland, 175 children with type 1 diabetes and 4859 control children completed a questionnaire on atopy experience, family composition and home environment. Control children from two age groups (6-8 yr old and 13-14 yr old) were identified from randomly selected primary and secondary schools across Northern Ireland. Cases were identified from a population-based type 1 diabetes register.


RESULTS
There was little evidence of a difference in the proportion of participants with a history of atopy in the cases compared with controls. There was a significant reduction in the risk of diabetes in children who lived with more siblings {odds ratio (OR) = 0.58 [95% confidence interval (95% CI) 0.39-0.85] in children who lived with three or more siblings compared with one or none} and in children who moved house more often [OR = 0.59 (95% CI 0.40-0.88) in children who moved house twice or more compared with never].


CONCLUSIONS
The reduced risk of type 1 diabetes in children living with siblings, sharing a bedroom and moving house more often could reflect the protection afforded by exposure to infections in early life and consequently may provide support for the hygiene hypothesis.
Cardwell
Chris R
CR
Department of Epidemiology and Public Health, School of Medicine and Dentistry, The Queen's University of Belfast, Belfast, UK. c.cardwell@qub.ac.uk
Carson
Dennis J
DJ
Yarnell
John
J
Shields
Mike D
MD
Patterson
Chris C
CC
D001249:Asthma / Q000150:complications / Q000453:epidemiology; D016022:Case-Control Studies; D002648:Child; D003876:Dermatitis, Atopic / Q000150:complications / Q000453:epidemiology*; D003922:Diabetes Mellitus, Type 1 / Q000453:epidemiology*; D004777:Environment; D005190:Family; D006798:Housing; D006801:Humans; D006920:Hygiene; D006969:Hypersensitivity, Immediate / Q000453:epidemiology*; D015994:Incidence; D009660:Northern Ireland / Q000453:epidemiology; D012042:Registries; D012307:Risk Factors; D035781:Siblings; D012959:Socioeconomic Factors; D011795:Surveys and Questionnaires