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Lower Baseline Risk Amplifies Relative Benefit of LDL-C Lowering in Primary Prevention
A systematic review and meta-analysis of 17 placebo-controlled trials involving 105,879 primary prevention participants found that the relative risk reduction (RRR) per 1 mmol/L LDL-C lowering is substantially greater at lower baseline cardiovascular event rates — falling from approximately 36% at a 1%/year event rate to just 13% at a 3%/year event rate. This inverse relationship between baseline risk and relative treatment benefit challenges the widely held assumption that lower-risk individuals have the least to gain from pharmacologic LDL-C lowering.
What Was Studied
The review investigated whether the relative cardiovascular benefit of pharmacologic LDL-C lowering — measured as RRR for three-point major adverse cardiovascular events (3P-MACE: cardiovascular death, non-fatal myocardial infarction, non-fatal stroke) per 1 mmol/L LDL-C reduction — varies systematically according to a population’s baseline cardiovascular event rate. A secondary aim quantified how much absolute LDL-C lowering would be required to achieve a 25% RRR at different levels of baseline risk.
How It Was Studied
This was a systematic review and meta-analysis drawing on searches of EMBASE, MEDLINE, and CENTRAL. Eligible studies were randomized, placebo-controlled lipid-lowering trials conducted in adults with no or low prior atherosclerotic cardiovascular disease prevalence (defined as less than 20%), making these purely or predominantly primary prevention populations. In total, 17 trials with 105,879 participants were included, with a mean participant age of 63.0 years and a median follow-up of 4.4 years. The included trials comprised 12 statin-only and 5 non-statin studies. Effect modification by placebo-arm event rate was evaluated using mixed-effects meta-regression at the trial level.
What Was Observed
- Relative benefit was strongly inversely related to baseline event rate. The RRR per 1 mmol/L LDL-C lowering declined markedly as background cardiovascular risk increased — from approximately 36% in populations with a 1%/year event rate down to approximately 13% in those with a 3%/year event rate. This gradient was identified through meta-regression across trials whose placebo event rates spanned a wide range of 0.52% to 3.78% per year.
- Greater absolute LDL-C reductions are needed in higher-risk populations to achieve equivalent relative benefit. A secondary meta-regression demonstrated that achieving a 25% RRR requires progressively larger absolute LDL-C reductions as the baseline event rate rises, quantifying the practical therapeutic implications of this risk-response relationship.
- The dataset represented a substantial and diverse evidence base. Across 17 trials, 6,076 3P-MACE events were recorded, and achieved LDL-C reductions ranged widely from 0.38 to 1.95 mmol/L, reflecting the heterogeneity of both the interventions used and the populations studied.
Why This Matters
Clinical practice and guideline frameworks have historically deprioritized LDL-C lowering in lower-risk primary prevention settings, partly on the grounds that absolute benefits appear modest when baseline event rates are low. These findings suggest that this framing may be incomplete: lower-risk individuals actually experience a greater proportional reduction in cardiovascular events per unit of LDL-C lowering, which the authors argue — alongside corroborating genetic evidence cited in the abstract — could support initiating therapy earlier. Conversely, in higher-risk primary prevention patients, achieving meaningful relative risk reductions demands substantially deeper LDL-C reductions than are often achieved in practice.
How to Read This Result
While the overall dataset is large and the direction of effect is consistent, the meta-regression was conducted at the aggregate trial level rather than using individual patient data, which limits the precision of the risk-stratified estimates and means residual confounding from differences between trials — including drug class, achieved LDL-C reduction, and population characteristics — cannot be fully excluded.
Limitations
The analysis pools 12 statin-only and 5 non-statin trials, introducing potential heterogeneity in mechanism and effect size that aggregate-level meta-regression cannot fully account for. Because the regression operates on trial-level summary data rather than individual patient records, within-trial variation in baseline risk is obscured, and the estimated risk-response gradient carries inherent imprecision. The wide range of achieved LDL-C reductions (0.38–1.95 mmol/L) and placebo event rates across trials may also introduce confounding that cannot be separated from the treatment effect gradient.