Type 2 diabetes risk may be increased by statin use in susceptible individuals

Long term use of statins is associated with an increased risk of developing type 2 diabetes in susceptible individuals, suggests a study recently published in BMJ Open Diabetes Research & Care. Data were collected from 3234 participants in the US Diabetes Prevention Program Outcomes Study (DPPOS). Regardless of the criteria leading to treatment initiation, the findings proved valid, suggesting that the reason for initiating statin treatment was not the underlying causative factor. 

This long-term study followed up a randomised clinical trial which looked at whether modest weight loss through lifestyle changes or treatment with metformin could reduce or delay development of type 2 diabetes in high risk individuals. Participants in the original trial were given advice on exercise and healthy eating and were randomised to either an intensive lifestyle programme or treated with metformin or placebo. Following completion, they were invited to take part in DPPOS, during which their serum lipids and blood pressure were measured annually. Blood glucose was measured twice a year, at which point new statin treatment was recorded.

At the start of DPPOS fewer than 4 per cent of participants were taking statins, but their use gradually increased; after 10 years around a third of the participants were taking them. The most commonly prescribed statins were simvastatin (40%) and atorvastatin (37%). The likelihood of a prescription rose substantially after a diagnosis of diabetes. However, statin use was found to be associated with a heightened risk of diabetes diagnosis, irrespective of which treatment group the participants had been in during the trial.

After taking account of the clinical criteria used to determine the need for statin treatment, the risk increase was quantified at 30%. Although those who were prescribed statins had slightly higher blood glucose levels to start with, this was insufficient to explain their higher rates of diabetes.

 To find out if the type of statin had any bearing on the risk of developing diabetes, the researchers grouped the drugs into low (pravastatin, lovastatin, fluvastatin) or high potency (atorvastatin, simvastatin, rosuvastatin, cerivastatin). There was no apparent link between the potency of the statin used and diabetes risk, nor between diabetes risk and the reduction in low density lipoprotein (LDL).

Due to the observational design, no firm conclusions can be drawn about causation. A statin prescription was based on an independent doctor’s assessment, and as such, patients were not randomly assigned to the treatment. As a possible explanation, the researchers point to experimental research suggesting that statins may impair insulin production, they also highlight that a potentially modest increase in diabetes risk needs to be weighed carefully against the known reductions in the risk of heart attack or stroke provided by statin treatment.