A maternal history of diabetes (MHx) has been reported to be more common in type 2 diabetes (T2DM) and associated with an earlier age of onset. In this study, we investigated how a paternal history of diabetes (PHx) might affect the age of onset and phenotype of diabetes. The records of 11,469 T2DM patients with self reported family history of diabetes prospectively entered in our computer database were analysed according to age of diabetes onset (Table 1). Positive parental history declines with age in all groups. Overall, 26.1% had a positive MHx, 17.2% had a positive PHx and 5.6% had both MHx and PHx. The predominance of MHx over PHx is much less for YT2DM (age of onset 15-29 years), evidenced by the MHx/PHx ratio falling from 2.03 in the oldest to 1.15 in the youngest onset group. To minimize inclusion of parental diabetes which developed after onset of diabetes in the proband, we also analysed the 57% of patients who were first seen within the age band of their diabetes diagnosis. This showed the same MHx vs PHx trend observed for the total cohort. In a subset of 187 YT2DM with clinical data for analysis, the presence or absence of PHx did not affect BMI, BP, Lipid profile, IHD, HbA1c, eGFR, ACR or retinopathy status after a median diabetes duration of 15.0(IQR: 6.9 – 24.7)years.

Our study confirms the greater overall maternal inheritance of T2DM, but this is less striking and not statistically significant in those with YT2DM. Therefore the relative contribution of paternal factors to YT2DM may be under-estimated if age of diabetes onset is not taken into consideration. Our observations suggest paternal factors contribute almost equally with maternal factors in the onset of YT2DM but do not appear to affect the risk factors or development of diabetes complications.