The use of metformin, insulin, sulphonylureas, and thiazolidinediones and the risk of fracture: Systematic review and meta-analysis of observational studies.

Certain glucose-lowering medications have been implicated in the risk of fracture. While there is convincing evidence from randomized controlled trials (RCTs) that thiazolidinedione use is associated with a higher risk of fracture, the effects of metformin, insulin, and sulphonylureas on the risk of fracture remain equivocal because these medications are not generally investigated in RCTs. A meta-analysis of observational studies to provide further insights into the association between the use of metformin, insulin, sulphonylureas, or thiazolidinediones and the risk of fracture was performed. PubMed and Web of Science databases were searched to identify relevant observational studies. A random effects model was used to estimate the summary relative risks (RRs) with 95% confidence intervals (CIs). The use of insulin (RR 1.49, 95% CI 1.29, 1.73; n = 23 studies), sulphonylureas (RR 1.30, 95% CI 1.18, 1.43; n = 10), and thiazolidinediones (RR 1.24, 95% CI 1.13, 1.35; n = 14) was associated with an increased risk of fracture, whereas the use of metformin was associated with a reduced risk of fracture (RR 0.86, 95% CI 0.75, 0.99; n = 12). Regarding types of thiazolidinediones, both pioglitazone (RR 1.38, 95% CI 1.23, 1.54; n = 5) and rosiglitazone (RR 1.34, 95% CI 1.14, 1.58; n = 5) were positively associated with the risk of fracture. In summary, there is compelling evidence to discourage the use of thiazolidinediones in individuals with an increased risk of fracture, whereas metformin appears to have a good safety profile for the risk of fracture. The reduced risk of fracture with metformin could possibly be due to the reduced overall risk of fracture among metformin users, as this medication is typically prescribed in the early stages of type 2 diabetes mellitus. The use of insulin or sulphonylureas may increase fracture risk; this risk is most likely attributed to an increased risk of hypoglycaemia-induced falls. Further confirmation by additional RCTs is required to determine whether the observed association between the use of metformin, insulin, or sulphonylureas and the risk of fracture is due to treatment with these medications or confounding factors.