Age of diagnosis does not alter the presentation or progression of robustly defined adult-onset type 1 diabetes

  

Aims

To determine whether presentation, progression and genetic susceptibility of robustly defined adult-onset type 1 diabetes (T1D) are altered by diagnosis age.

Methods 

We compared the relationship between diagnosis age and presentation, C-peptide loss (annual change in Urine C-peptide Creatinine Ratio (UCPCR)) and genetic susceptibility (T1D genetic risk Score (T1DGRS)) in adults with confirmed T1D in the prospective StartRight study, 1,798 adults with new-onset diabetes. T1D was defined in two ways: ≥2 positive islet-autoantibodies (of GADA, IA-2A, ZNT8A) irrespective of clinical diagnosis(n=385), or 1 positive islet-autoantibody and a clinical diagnosis of T1D(n=180). 

Results 

In continuous analysis age of diagnosis was not associated with C-peptide loss for either definition of T1D [p>0.1], with mean(95% CI) annual C-peptide loss in those diagnosed before and after age 35 (median age of T1D defined by ≥2 positive autoantibodies): 39(31-46)% vs 44(38-50)% with ≥2 positive islet-autoantibodies and 43(33-51)% vs 39(31-46)% with clinician diagnosis confirmed by 1 positive islet-autoantibody [p>0.1]. Baseline C-peptide and T1DGRS were unaffected by age of diagnosis or T1D definition [p>0.1]. In T1D defined by ≥2 autoantibodies, presentation severity was similar in those diagnosed before and after age 35: unintentional weight loss 80(95% CI 74-85)% vs 82(76-87)%, ketoacidosis 23(17-29)% vs 19(14-25)% and presentation glucose 21(19-22) mmol/l vs 21(20-22) mmol/l [all p≥0.1]. Despite similar presentation, older adults were less likely to be diagnosed with T1D, insulin treated, or admitted to hospital.  

Conclusions 

When adult-onset T1D is robustly defined the presentation characteristics, progression, and T1D genetic susceptibility are not altered by age of diagnosis.