Elevated LDL cholesterol and increased risk of myocardial infarction and atherosclerotic cardiovascular disease in individuals aged 70-100 years: a contemporary primary prevention cohort

Abstract

Background: Findings of historical studies suggest that elevated LDL cholesterol is not associated with increased risk of myocardial infarction and atherosclerotic cardiovascular disease in patients older than 70 years. We aimed to test this hypothesis in a contemporary population of individuals aged 70-100 years.

Methods: We included in our analysis individuals (aged 20-100 years) from the Copenhagen General Population Study (CGPS) who did not have atherosclerotic cardiovascular disease or diabetes at baseline and who were not taking statins. Standard hospital assays were used to measure LDL cholesterol. We calculated hazard ratios (HRs) and absolute event rates for myocardial infarction and atherosclerotic cardiovascular disease, and we estimated the number needed to treat (NNT) in 5 years to prevent one event.

Findings: Between Nov 25, 2003, and Feb 17, 2015, 91 131 individuals were enrolled in CGPS. During mean 7·7 (SD 3·2) years of follow-up (to Dec 7, 2018), 1515 individuals had a first myocardial infarction and 3389 had atherosclerotic cardiovascular disease. Risk of myocardial infarction per 1·0 mmol/L increase in LDL cholesterol was augmented for the overall population (HR 1·34, 95% CI 1·27-1·41) and was amplified for all age groups, particularly those aged 70-100 years. Risk of atherosclerotic cardiovascular disease was also raised per 1·0 mmol/L increase in LDL cholesterol overall (HR 1·16, 95% CI 1·12-1·21) and in all age groups, particularly those aged 70-100 years. Risk of myocardial infarction was also increased with a 5·0 mmol/L or higher LDL cholesterol (ie, possible familial hypercholesterolaemia) versus less than 3·0 mmol/L in individuals aged 80-100 years (HR 2·99, 95% CI 1·71-5·23) and in those aged 70-79 years (1·82, 1·20-2·77). Myocardial infarction and atherosclerotic cardiovascular disease events per 1000 person-years for every 1·0 mmol/L increase in LDL cholesterol were highest in individuals aged 70-100 years, with number of events lower with younger age. The NNT in 5 years to prevent one myocardial infarction or atherosclerotic cardiovascular disease event if all people were given a moderate-intensity statin was lowest for individuals aged 70-100 years, with the NNT increasing with younger age.

Interpretation: In a contemporary primary prevention cohort, people aged 70-100 years with elevated LDL cholesterol had the highest absolute risk of myocardial infarction and atherosclerotic cardiovascular disease and the lowest estimated NNT in 5 years to prevent one event. Our data are important for preventive strategies aimed at reducing the burden of myocardial infarction and atherosclerotic cardiovascular disease in the growing population aged 70-100 years.

Funding: None.