Objectives The aim of this retrospective cohort study was to quantify the risk of incident type II DM in patients with RA treated with oral GCs, and its relationship with dose.
Methods Adult patients with RA were identified from a large UK primary care research database, the Clinical Practice Research Database (CPRD) using a validated algorithm during the study period 01/92-12/09. Patients with prevalent DM at the time of their first code for RA were excluded. GC exposure from first code for RA was considered using several models including a time-varying binary indicator of ever or current use, current daily dose, average daily dose and cumulative dose. Incident DM was defined as a READ code for type II DM, at least two oral anti-diabetic prescriptions or abnormal blood results (blood sugar, HbA1C or glucose tolerance test). Gender, age, BMI, smoking status, family history of DM, hypertension, prior cumulative dose of oral GC, current DMARDs and ever NSAID use were potential confounders. Multiple imputations were used to impute missing data for BMI and smoking status. Incidence rates for type II DM were calculated for different patterns of GC exposure. Crude and adjusted Hazard Ratios (HR) were estimated using Cox regression.
Results 23,736 adult RA patients were included. 70% were female with a median age of 59 years (IQR 49-71). Median time at risk per patient was 5.39 years (Range: 0.003-18.0). 2,462 patients were diagnosed with type II DM during follow-up: incidence 14.0 events/1000 person years (pyrs) in unexposed patients and 21.9 events/1000pyrs in time following GC exposure. The crude HR was 1.53 (95%CI 1.41-1.66) in ever GC users compared with non-use. After adjusting for all covariates, the HR reduced to 1.38 (95%CI 1.27-1.51). This equates to one additional case of DM per year for every 185 patients currently receiving GCs. Each 5mg increase of current oral GC was associated with a 14% increased risk of DM (HR:1.14; 95%CI 1.11-1.17). Patients currently taking between 10-30mg/day had an adjusted HR of 1.95 (95%CI 1.62-2.34) compared to non-use, equating to one additional case of DM for every 67 patients treated. A 5mg increase in average daily dose was associated with a 32% increased risk (HR 1.32; 95%CI 1.26-1.39), suggesting prolonged exposure increased risk.
Conclusions Oral GC therapy is a significant and clinically important risk factor for incident Type II DM in patients with RA. Screening for DM might be warranted in patients taking oral GC therapy.
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Disclosure of Interest None Declared
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