Aims/Introduction The bone mineral density in patients with type 1 diabetes mellitus is reduced due to impaired insulin secretion. However, it is unclear whether the rate of bone mineral density reduction is affected by the type 1 diabetes mellitus subtype. This study aimed to clarify the difference in bone mineral density across type 1 diabetes mellitus subtypes: slowly progressive (SP), acute-onset (AO), and fulminant (F). Methods This was a retrospective, single-center, cross-sectional study conducted on 98 adult type 1 diabetes mellitus patients. The main outcome included the bone mineral density Z-score (BMD-Z) measured at the lumbar spine and femoral neck. Results The lumbar spine BMD-Z was lower in the acute-onset than in the slowly progressive subtype (P = 0.03). No differences were observed when compared with the fulminant subtype. The femoral neck BMD-Z tended to be higher in the slowly progressive than in the acute-onset and fulminant subtypes. Multiple regression analyses showed that the lumbar spine BMD-Z was associated with subtypes (AO vs SP) (P = 0.01), but not subtypes (F vs SP), adjusted for sex, duration, retinopathy, and C-peptide immunoreactivity (CPR). When the patients were divided into disease duration tertiles, in the first and second tertiles, the CPR levels were lower in the acute-onset or fulminant than in the slowly progressive subtype. In contrast, the lumbar spine and femoral neck BMD-Z differed between the acute-onset and slowly progressive only in the second tertiles (both P
