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Hypercholesterolemia paradox in relation to mortality in acute coronary syndrome
Tracy Y Wang1, L Kristin Newby, Anita Y Chen
1Division of Cardiology, Duke Clinical Research Institute, Duke University Medical Center, Durham, North Carolina 27705, USA. wang0085@mc.duke.edu
Insights
Hypercholesterolemia is linked to better outcomes in acute coronary syndromes, but this association may be due to confounding factors, not a protective effect. Further research is needed to understand this paradox in cardiovascular disease.
Area of Science:
- Cardiology
- Clinical Research
- Public Health
Background:
- Hypercholesterolemia is a known risk factor for coronary artery disease.
- Paradoxically, hypercholesterolemia is associated with reduced adverse outcomes in patients with acute coronary syndromes (ACS).
Purpose of the Study:
- To investigate the association between hypercholesterolemia and in-hospital mortality in patients with non-ST-segment elevation ACS.
- To explore the reasons behind the observed paradox of better outcomes in hypercholesterolemic ACS patients.
Main Methods:
- Analysis of 84,429 patients from the Can Rapid Risk Stratification of Unstable Angina Patients Suppress Adverse Outcomes with Early Implementation of the American College of Cardiology/American Heart Association Guidelines registry.
- Examined the association between a history of hypercholesterolemia and in-hospital mortality, adjusting for clinical covariates.
- Repeated the analysis for newly diagnosed hypercholesterolemia (in-hospital LDL-C ≥ 100 mg/dL) in patients without prior diagnosis.
Main Results:
- A history of hypercholesterolemia was associated with significantly lower in-hospital mortality, persisting after multivariable adjustment.
- Among patients with no prior hypercholesterolemia diagnosis, newly diagnosed hypercholesterolemia showed a non-significant trend towards lower mortality after adjustment.
- The protective association of hypercholesterolemia with outcomes may be influenced by confounding clinical characteristics and prior medical contact.
Conclusions:
- The observed association of hypercholesterolemia with better outcomes in ACS patients presents a challenge for observational studies.
- Confounding factors, including other clinical characteristics, statin treatment, and increased prior medical contact, likely contribute to this paradox.
- Hypercholesterolemia's apparent protective effect may not be a direct biological benefit but rather a marker of patient characteristics or healthcare utilization.
Background:
Hypercholesterolemia is a risk factor for coronary artery disease, yet is associated with lower risk of adverse outcomes in patients with acute coronary syndromes (ACS).
Hypothesis:
We explored this paradox in 84,429 patients with non-ST-segment elevation ACS in the Can Rapid Risk Stratification of Unstable Angina Patients Suppress Adverse Outcomes with Early Implementation of the American College of Cardiology/American Heart Association Guidelines registry.
Methods:
We examined the association between a history of hypercholesterolemia and in-hospital mortality after adjusting for clinical covariates. After excluding patients with previously diagnosed hypercholesterolemia, we repeated the analysis, examining the association between newly diagnosed hypercholesterolemia (in-hospital low-density lipoprotein cholesterol [LDL-C] > or = 100 mg/dL) and mortality.
Results:
A history of hypercholesterolemia was associated with lower in-hospital mortality (unadjusted odds ratio [OR]: 0.58; 95% confidence interval [CI]: 0.55, 0.62). This protective association persisted after adjusting for baseline characteristics (OR: 0.71; 95% CI: 0.66, 0.76) and prior statin use (OR: 0.74; 95% CI: 0.68, 0.80). Among 22,711 patients with no history of hypercholesterolemia, 12,809 had a new in-hospital diagnosis of hypercholesterolemia. Unadjusted mortality in these patients was lower than among those with normal LDL levels (OR: 0.58; 95% CI: 0.50, 0.67); however, this difference was not significant after multivariable adjustment (OR: 0.86; 95% CI: 0.73, 1.01).
Conclusions:
The association of hypercholesterolemia with better outcomes highlights a major challenge in observational analyses. Our results suggest this paradox may result from confounding due to other clinical characteristics, impact of statin treatment, and perhaps most importantly, the fact that previously diagnosed hypercholesterolemia is a marker for patients with more prior medical contact.
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