Hypercholesterolemia paradox in relation to mortality in acute coronary syndrome.
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).


OBJECTIVE
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.
Wang
Tracy Y
TY
Division of Cardiology, Duke Clinical Research Institute, Duke University Medical Center, Durham, North Carolina 27705, USA. wang0085@mc.duke.edu
Newby
L Kristin
LK
Chen
Anita Y
AY
Mulgund
Jyotsna
J
Roe
Matthew T
MT
Sonel
Ali F
AF
Bhatt
Deepak L
DL
DeLong
Elizabeth R
ER
Ohman
E Magnus
EM
Gibler
W Brian
WB
Peterson
Eric D
ED
D054058:Acute Coronary Syndrome / Q000097:blood / Q000209:etiology / Q000401:mortality*; D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000097:blood; D008078:Cholesterol, LDL / Q000097:blood*; D015986:Confounding Factors, Epidemiologic; D005260:Female; D017052:Hospital Mortality; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000627:therapeutic use; D006937:Hypercholesterolemia / Q000097:blood / Q000150:complications / Q000175:diagnosis / Q000188:drug therapy / Q000401:mortality*; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D012042:Registries; D012189:Retrospective Studies; D018570:Risk Assessment; D012307:Risk Factors
D015415:Biomarkers; D008078:Cholesterol, LDL; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors