Population-wide cohort study of statin use for the secondary cardiovascular disease prevention in Scotland in 2009-2017

Abstract

Objective: To estimate the extent of suboptimal statin use for the secondary prevention of atherosclerotic cardiovascular disease (ASCVD) at different stages of the treatment pathway and identify patient groups at risk of suboptimal treatment.

Methods: National retrospective cohort study using linked National Health Service Scotland administrative data of adults hospitalised for an ASCVD event (n=167 978) from 2009 to 2017. Proportions of patients initiating, adhering to, discontinuing and reinitiating statins were calculated. We separately examined treatment following myocardial infarction (MI), ischaemic stroke and peripheral arterial disease (PAD) hospitalisations. Multivariable logistic regression and Cox proportional hazards models were used to assess the roles of patient characteristics in the likelihood of initiating and discontinuing statins.

Results: Of patients hospitalised with ASCVD, only 81% initiated statin therapy, 40% of whom used high-intensity statin. Characteristics associated with lower odds of initiation included female sex (28% less likely than men), age below 50 years or above 70 years (<50 year-olds 26% less likely, and 70-79, 80-89 and ≥90 year-olds 22%, 49% and 77% less likely, respectively, than 60-69 year-olds), living in the most deprived areas and history of mental health-related hospital admission. Following MI, 88% of patients initiated therapy compared with 81% following ischaemic stroke and 75% following PAD events. Of statin-treated individuals, 24% discontinued treatment. Characteristics associated with discontinuation were similar to those related to non-initiation.

Conclusions: Statin use remains suboptimal for the secondary ASCVD prevention, particularly in women and older patients, and following ischaemic stroke and PAD hospitalisations. Improving this would offer substantial benefits to population health at low cost.

Keywords: Coronary Artery Disease; Medication Adherence; Quality of Health Care; STATINS; Stroke.

Figure 1

Schematic of the outcome measures initiation, adherence, discontinuation and reinitiation. PDC, proportion of days covered.

Figure 2

Statin initiation and discontinuation rates following atherosclerotic cardiovascular disease (ASCVD) event.

Figure 3

Statin initiation rates following atherosclerotic cardiovascular disease (ASCVD) event in Scotland in 2009–2017, by calendar period, sex, age and statin intensity. There was evidence of an increase in the proportion of individuals initiating any statin over time based on the Cochran-Armitage test for trend (overall: men: p<0.001; women: p<0.5; age <50: p<0.5; age 50-59: p<0.001; age 60-69: p<0.001; age 70-79: p<0.001; age 80-89: p<0.001). There was also strong evidence of an increase in the proportion of statin initiators using high-intensity statin therapy vs. low/medium-intensity therapy (overall and in every sex and age group: p<0.001).

Figure 4

Associations of patient characteristics with statin initiation among individuals with atherosclerotic cardiovascular disease (ASCVD): a multivariable logistic regression model. The Charlson Comorbidity Index (CCI) results presented in this figure are not easily interpretable due to index MI, stroke and PAD included among the CCI-eligible comorbidities, leaving the remaining index ASCVD conditions in the comparator “no comorbidity” category.

Figure 5

Associations of patient characteristics with statin discontinuation among individuals with atherosclerotic cardiovascular disease (ASCVD): a multivariable Cox proportional hazards model. The Charlson Comorbidity Index (CCI) results presented in this figure are not easily interpretable due to index MI, stroke and PAD included among the CCI-eligible comorbidities, leaving the remaining index ASCVD conditions in the comparator “no comorbidity” category.