What is the clinical evidence from this study?

Study design: Observational. Population: Healthy (n=448). Intervention: Low- and high-density lipoprotein cholesterol levels vs. Smoking status (current vs ex- or nonsmokers). Primary outcome: Carotid intima-media thickness (IMT) (p=0.001).

What does this research mean for the field?

The association between cholesterol levels and carotid intima-media thickness (IMT) differs by smoking status, with LDL-C levels significantly impacting IMT in current smokers but not nonsmokers, while HDL-C levels impact IMT in nonsmokers but not current smokers. Novelty: ClaimNovelty.INCREMENTAL. Consensus alignment: ConsensusAlignment.NEUTRAL.

January 1, 2012Open Access

Impact of Low-and High-Density Lipoprotein Cholesterol Levels on Carotid Intima-Media Thickness Differs by Smoking Status in Middle-Aged Men

THTaichiro HayaseOhkawara Neurosurgical Hospital MAMakoto AyaoriJikei University School of Medicine HSHiroki SatoOkayama University

Key Result

LDL-C levels were significantly associated with carotid IMT in current smokers (p=0.001) but not nonsmokers, whereas HDL-C was associated with IMT in nonsmokers but not current smokers.

Study Design

Type

Observational (n=448)

Structured PICO

Does the association between LDL-C and HDL-C levels and carotid intima-media thickness differ by smoking status in healthy middle-aged men?

Population

448 healthy middle-aged male military personnel (aged 37 to 61, mean age 50.4), free of cardiovascular and cerebrovascular diseases, acute and chronic inflammatory diseases, neoplastic diseases, renal dysfunction (eGFR < 60 mL/min/1.73 m2), and not taking routine medication.

Outcome

Carotid intima-media thickness (mean and max IMT) measured by B-mode ultrasoundsurrogate

The atherogenic impact of LDL-C on carotid intima-media thickness is more pronounced in current smokers, whereas the protective association of HDL-C is only evident in non-smokers and ex-smokers.

Main Result

p-value: p=0.001

Abstract

AIM: Cigarette smoking is a strong risk factor for atherosclerotic disease; however, it remains unclear whether the impact of other risk factors differs by smoking status. The aim of this study was to investigate this issue, especially with regard to low-density and high-density lipoprotein (LDL/HDL) levels. METHODS: In total, 448 healthy, middle-aged men (aged 37 to 61) participated in this study. Smoking habits were recorded, carotid intima-media thickness (IMT) was measured by B-mode ultrasound, and serum lipids and other biochemical parameters were determined from fasted blood samples. RESULTS: Among the overall subjects, multivariate regression analyses showed that IMT was significantly associated with age (p < 0.0001 for mean IMT, p= 0.002 for max IMT), body mass index (BMI, mean IMT, p= 0.028), LDL-C levels (mean/max IMT, p= 0.001), HDL-C levels (max IMT, p= 0.022) and current smoking habit (mean IMT, p=0.012). Subgroup analyses according to smoking status revealed that LDL-C levels were significantly associated with mean/max IMT in current smokers (p=0.001) but not in ex- or nonsmokers (never smoked subjects). After adjusting for age, BMI, systolic blood pressure, hemoglobin A1c and serum lipids, mean IMT respectively increased and decreased progressively across LDL-C and HDL-C quartiles (p= 0.004 and 0.045) in the overall subjects. These associations were observed in current smokers (p= 0.01) but not in ex- or nonsmokers for LDL-C, and were observed in ex- and nonsmokers (p= 0.025, 0.017, respectively) but not in current smokers for HDL-C. CONCLUSION: The impact of LDL-C/HDL-C levels on carotid IMT differs by smoking status. These observations imply that distinct mechanisms are involved in the (anti) atherogenesis of LDL/HDL according to smoking status.

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