title: Impact of low-and high-density lipoprotein cholesterol levels on carotid intima-media thickness differs by smoking status in middle-aged men.
abstract: OBJECTIVE
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Division of Anti-aging, Department of Internal Medicine, National Defense Medical College, Tokorozawa, Japan.
authors.forename: Taichiro
authors.initials: T
authors.lastname: Hayase
authors.forename: Makoto
authors.initials: M
authors.lastname: Ayaori
authors.forename: Hiroki
authors.initials: H
authors.lastname: Sato
authors.forename: Nobukiyo
authors.initials: N
authors.lastname: Tanaka
authors.forename: Koichiro
authors.initials: K
authors.lastname: Ohashi
authors.forename: Harumi
authors.initials: H
authors.lastname: Uto-Kondo
authors.forename: Katsunori
authors.initials: K
authors.lastname: Ikewaki
authors.forename: Fumitaka
authors.initials: F
authors.lastname: Ohsuzu
mesh_terms: D017536:Carotid Artery, Common / Q000187:drug effects*; D059168:Carotid Intima-Media Thickness; D008076:Cholesterol, HDL / Q000097:blood*; D008078:Cholesterol, LDL / Q000097:blood*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012907:Smoking / Q000009:adverse effects*; D017539:Tunica Intima / Q000187:drug effects*; D017540:Tunica Media / Q000187:drug effects*
chemical_list: D008076:Cholesterol, HDL; D008078:Cholesterol, LDL