Time trends in the prescription of statins for the primary prevention of cardiovascular disease in the United Kingdom: a cohort study using The Health Improvement Network primary care data

Introduction

Statins – a large class of cholesterol-lowering drugs – are widely prescribed for the primary prevention of cardiovascular disease (CVD).^1,2 Since the 1990s, a number of clinical trials and large-scale studies have demonstrated the effectiveness of statins for CVD prevention^3–6 and, in recent years, statins have become one of the most regularly prescribed medicines in the UK.⁷ In January 2006, the UK government's National Institute for Health and Care Excellence (NICE) issued guidelines suggesting that statins should be prescribed by general practitioners (GPs – UK family doctors) to adults aged under 75 years whose risk of developing CVD within 10 years exceeds 20%.⁸ Generally, the 10-year risk of developing CVD is calculated using an ­established risk prediction method, such as the Framingham risk score⁹ or QRISK/QRISK2 risk calculators.^10–12 In July 2014, this guideline was adjusted, with the statin prescription risk score threshold reduced to a risk of 10%. For the over 75s, the same NICE guidelines have recommended that statin prescriptions should be considered irrespective of the 10-year CVD risk score.

Clearly, statins have been commonly prescribed in the UK and the NICE guidelines have recommended their use for a wide section of the UK population. However, despite this, few studies have investigated the rate at which statin therapy is initiated, the prevalence of statin prescriptions, and how these may have changed over time. Some studies on trends in statins prescription in the UK were undertaken during the late 1990s and early 2000s, mainly using small data sources.^13–16 Other past works have examined statin prescription trends within Europe,^17–24 Canada,²⁵ and the US,^26–28 though, again, with either relatively small cohorts or not with the aim of examining statin prescription trends over time.

In this study, we attempt a comprehensive, large-scale assessment of prescribing trends for statins over time within the UK. We examine both the rate of statin therapy initiation (the rate at which subjects begin the use of statins) and the prevalence of statin prescriptions over time for the primary prevention of CVD. In addition, we examine possible differences in trends over time with respect to sex, age group, and level of socioeconomic deprivation. We use data from a large cohort of individuals that...