(HealthDay)—There is considerable variation in adherence across medication classes for the treatment of type 2 diabetes (T2D), according to a review published online Nov. 14 in Diabetes, Obesity and Metabolism.

Andrew McGovern, B.M.B.S., from the University of Surrey in Guildford, U.K., and colleagues conducted a systematic literature review of observational studies comparing medication or persistence between two or more glucose-lowering medications in individuals with T2D. Data were included for 48 studies.

The researchers found that adherence was better for sulfonylureas and thiazolidinediones compared with metformin (mean difference, 10.6 percent [95 percent confidence interval [CI], 6.5 to 14.7 percent] and 11.3 percent [95 percent CI, 2.7 to 20.0 percent], respectively). Compared with sulfonylureas, thiazolidinedione adherence was marginally better (mean difference, 1.5 percent; 95 percent CI, 0.1 to 2.9 percent). Adherence was better for dipeptidyl peptidase-4 inhibitors than sulfonylureas and thiazolidinediones. Compared with long-acting analogue insulins, glucagon-like peptide-1 receptor agonists had a higher odds ratio for discontinuation (1.95 [95 percent CI, 1.17 to 3.27]). Better persistence was seen for long-acting insulin analogues versus human insulins (mean difference, 43.1 days [95 percent CI, 22.0 to 64.2 days]). There was considerable variability in the methods for defining adherence and persistence.

"Adherence varies considerably across different classes used for the treatment of T2D," the authors write.

Several authors disclosed financial ties to the pharmaceutical industry.