BackgroundIn 2014, the National Institute for Health and Care Excellence (NICE) changed the recommended threshold for initiating statins from a 10-year risk of cardiovascular disease (CVD) of 20% to 10% (Clinical Guideline 181), making 4.5 million extra people eligible for treatment.AimTo evaluate the impact of this guideline change on statin prescribing behaviour.Design and settingA descriptive study using data from Clinical Practice Research Datalink (CPRD), a primary care database in England.MethodPeople aged 25–84 years being initiated on statins for the primary prevention of CVD were identified. CVD risk predictions were calculated for every person using data in their medical record (calculated risks), and were extracted directly from their medical record if a QRISK score was recorded (coded risks). The 10-year CVD risks of people initiated on statins in each calendar year were compared.ResultsThe average ‘calculated risk’ of all people being initiated on statins was 20.65% in the year before the guideline change, and 20.27% after. When considering only the ‘coded risks’, the average risk was 21.85% before the guideline change, and 18.65% after. The proportion of people initiating statins that had a coded risk score in their medical record increased significantly from 2010–2017.ConclusionCurrently available evidence, which only considers people with coded risk scores in their medical record, indicates the guideline change had a large impact on statin prescribing. However, that analysis likely suffers from selection bias. This new evidence indicates only a modest impact of the guideline change. Further qualitative research about the lack of response to the guideline change is needed.