Objectives: To examine how life course factors may be associated with risk of paediatric T1DM onset.
Methods: Case recruitment of the type 1 diabetes cases commenced in 2008 and finished in 2011 (response rate 77% (333/434)). Hospital control (day surgery attendees with minor conditions) participation rates were also high - full questionnaire data and venous blood samples available on 87% (573/661) of eligible children). Community control recruitment was also conducted 2008-2011.
Results: Adjusting for age and sex, T1DM cases compared to hospital controls were more likely to be Caucasian (AOR) 2.28 (1.42, 3.65); have fairer skin, p< 0.001; and blue/grey eye colour, p< 0.001. Similar phenotype patterns were observed between T1DM cases to community controls. With regard to parent reported life course sun exposure, patterns were less evident but there was some indication, adjusting for age, sex, skin type and ethnicity, that higher sun exposure during winter holidays was associated with decreased T1DM risk compared to hospital controls particularly in early adolescence (p trend per category increase (< 1hr, 1-2hr, 2-3hr, more than 3 hours)=0.84 (0-2 years), 0.06 (3-5 years), 0.12 (6-9 years) and 0.03 (11-15 years)). Our preliminary analysis of archived neonatal blood spots (n=184), indicates ambient UVR levels in the 6 months before birth accounts for 23% of the variation of 25OHD levels in the dried blood spots. Analysis of a second biomarker, sun-induced eye corneal change, is ongoing but our preliminary analysis indicates an increase in biomarker level with age and history of past sun exposure. During 2012, viral and cytokine profiles and candidate gene variants will be assessed.
Conclusion: T1DM cases have a different skin phenotype than healthy controls at presentation. Further work will assess how this reflects sun exposure, sun sensitivity and vitamin D levels at birth and at the time of first T1DM presentation.