title: Low plasma coenzyme Q(10) levels and breast cancer risk in Chinese women.
abstract: BACKGROUND
  Low circulating levels of coenzyme Q(10) (CoQ(10)) have been associated with increased cancer incidence and poor prognosis for a number of cancer types, while a recent prospective study observed a positive association for CoQ(10) with breast cancer risk.
  
  
  METHODS
  We prospectively examined the association of plasma CoQ(10) with breast cancer risk in a nested case-control study of Chinese women within the Shanghai Women's Health Study (SWHS). Prediagnostic plasma samples were obtained from 340 cases and 653 age-matched controls and analyzed for total CoQ(10).
  
  
  RESULTS
  A borderline significant inverse association for breast cancer incidence with plasma CoQ(10) level was observed by a conditional logistic regression model adjusted for age and age at first live birth, which became significant after elimination of cases diagnosed within 1 year of blood draw (P(trend) = 0.03). This association was independent of menopausal status. Plasma CoQ(10) levels were also observed to be significantly associated with circulating γ-tocopherol (r = 0.50; P < 0.0001) and α-tocopherol (r = 0.38; P < 0.0001) levels.
  
  
  CONCLUSIONS
  Circulating levels of CoQ(10) were generally low in this population and the observed association with breast cancer risk may be limited to those women with exceptionally low values.
  
  
  CONCLUSIONS
  This study reports an inverse relationship between circulating CoQ(10) and breast cancer risk, while the only other prospective study of CoQ(10) and breast cancer to date found a positive association. Lower levels of CoQ(10) in the SWHS population suggest that the 2 studies may not be contradictory and indicate a possible nonlinear (U-shaped) association of CoQ(10) with risk.
authors.affiliation: Office of Public Health Studies, John A. Burns School of Medicine, University of Hawaii at Manoa, Honolulu, Hawaii 96822, USA. rvcooney@hawaii.edu
authors.forename: Robert V
authors.initials: RV
authors.lastname: Cooney
authors.forename: Qi
authors.initials: Q
authors.lastname: Dai
authors.forename: Yu-Tang
authors.initials: YT
authors.lastname: Gao
authors.forename: Wong-Ho
authors.initials: WH
authors.lastname: Chow
authors.forename: Adrian A
authors.initials: AA
authors.lastname: Franke
authors.forename: Xiao-Ou
authors.initials: XO
authors.lastname: Shu
authors.forename: Honglan
authors.initials: H
authors.lastname: Li
authors.forename: Butian
authors.initials: B
authors.lastname: Ji
authors.forename: Qiuyin
authors.initials: Q
authors.lastname: Cai
authors.forename: Weiwen
authors.initials: W
authors.lastname: Chai
authors.forename: Wei
authors.initials: W
authors.lastname: Zheng
mesh_terms: D000328:Adult; D000368:Aged; D044466:Asian People; D001940:Breast / Q000378:metabolism*; D001943:Breast Neoplasms / Q000097:blood* / Q000175:diagnosis*; D016022:Case-Control Studies; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008875:Middle Aged; D011379:Prognosis; D011446:Prospective Studies; D014451:Ubiquinone / Q000031:analogs & derivatives* / Q000097:blood / Q000172:deficiency; D024502:alpha-Tocopherol / Q000097:blood
chemical_list: D014451:Ubiquinone; C024989:coenzyme Q10; D024502:alpha-Tocopherol