Background: The salutary effects of statin therapy in patients with cardiovascular disease (CVD) are well established. Although generally considered safe, statin therapy has been reported to contribute to induction of diabetes mellitus (DM).

Objectives: To assess the risk-benefit of statin therapy, prescribed for the prevention of CVD, in the development of DM.

Methods: In a population-based real-life study, the incidence of DM and CVD were assessed retrospectively among 265,414 subjects aged 40–70 years, 17.9% of whom were treated with statins. Outcomes were evaluated according to retrospectively determined baseline 10 year cardiovascular (CV) mortality risks as defined by the European Systematic COronary Risk Evaluation, statin dose-intensity regimen, and level of drug adherence.

Results: From 2010 to 2014, 5157 (1.9%) new cases of CVD and 11,637 (4.4%) of DM were observed. Low-intensity statin therapy with over 50% adherence was associated with increased DM incidence in patients at low or intermediate baseline CV risk, but not in patients at high CV risk. In patients at low CV risk, no CV protective benefit was obtained. The number needed to harm (NNH; incident DM) for low-intensity dose regimens with above 50% adherence was 40. In patients at intermediate and high CV risk, the number needed to treat was 125 and 29; NNH was 50 and 200, respectively.

Conclusions: Prescribing low-dose statins for primary prevention of CVD is beneficial in patients at high risk and may be detrimental in patients at low CV risk. In patients with intermediate CV risk, our data support current recommendations of individualizing treatment decisions.