Risk of diabetes mellitus associated with use of oral glucocorticoids in patients with polymyalgia rheumatica and giant cell arteritis

Background: Oral glucocorticoid (GC) use can induce diabetes mellitus (DM). Patients with polymyalgia rheumatica (PMR) and giant cell arteritis (GCA) are both treated with GCs and can develop DM. However, it is not known whether the DM risk differs with prescribing choices such as GC dose or duration. Objectives: (1) To quantify DM risk associated with dose and duration of oral GC in PMR/GCA patients within the first two years of diagnosis, using Clinical Practice Research Datalink (CPRD). (2) To explore prescribing patterns of oral GCs for PMR/GCA patients in primary care. (3) To compare CPRD-derived prescription data with extracted data from primary care prescription data. Methods: (1) The impact of GC dose and duration on DM risk was explored using the extended time-varying Cox model. The additional risk associated with the timing of GC exposure was determined using the rolling cumulative dose and weighted cumulative exposure models. The risk was compared between patients on high GC dose versus low GC dose. (2) The total monthly oral GC dose was calculated and compared with clinical guidelines. (3) The CPRD-derived prescription data and my extracted data were compared. Results: (1) When compared patients on high dose versus low dose regimens, DM risk was increased by 1.4-2.5-fold within the most recent ten months for PMR patients; and 1.6-2.8-fold within the most recent five months for patients with GCA (with or without PMR). (2) PMR prescribing was broadly in line with guidelines, but starting doses prescribed for GCA in primary care were lower than guidelines. (3) Data from the CPRD-derived prescriptions were similar to my extracted data. Conclusion: Higher GC dose was associated with an elevated risk of new DM in PMR/GCA patients within the initial two years of diagnosis. Treatment strategies to reduce cumulative GC dose should be investigated.