Age-dependent decline of β-cell function in type 1 diabetes after diagnosis: a multi-centre longitudinal study

C-peptide secretion is currently the only available clinical biomarker to measure residual β-cell function in type 1 diabetes. However, the natural history of C-peptide decline after diagnosis can vary considerably dependent upon several variables. We investigated the shape of C-peptide decline over time from type 1 diabetes onset in relation to age at diagnosis, haemoglobin A1c (HbA1c) levels and insulin dose.

We analysed data from 3929 type 1 diabetes patients recruited from seven European centres representing all age groups at disease onset (childhood, adolescence and adulthood). The influence of the age at onset on β-cell function was investigated in a longitudinal analysis at diagnosis and up to 5-years follow-up.

Fasting C-peptide (FCP) data at diagnosis were available in 3668 patients stratified according to age at diagnosis in four groups (<5 years, n = 344; >5 years < 10 years, n = 668; >10 years < 18 years, n = 991; >18 years, n = 1655). FCP levels were positively correlated with age (p < 0.001); the subsequent decline in FCP over time was log-linear with a greater decline rate in younger age groups (p < 0.0001).

This study reveals a positive correlation between age at diagnosis of type 1 diabetes and FCP with a more rapid decline of β-cell function in the very young patients. These data can inform the design of clinical trials using C-peptide values as an end-point for the effect of a given treatment.