title: Smoking-Associated DNA Methylation Biomarkers and Their Predictive Value for All-Cause and Cardiovascular Mortality.
abstract: BACKGROUND
  With epigenome-wide mapping of DNA methylation, a number of novel smoking-associated loci have been identified.
  
  
  OBJECTIVE
  We aimed to assess dose-response relationships of methylation at the top hits from the epigenome-wide methylation studies with smoking exposure as well as with total and cause-specific mortality.
  
  
  METHODS
  In a population-based prospective cohort study in Germany, methylation was quantified in baseline blood DNA of 1,000 older adults by the Illumina 450K assay. Deaths were recorded during a median follow-up of 10.3 years. Dose-response relationships of smoking exposure with methylation at nine CpGs were modeled by restricted cubic spline regression. Associations of individual and aggregate methylation patterns with all-cause, cardiovascular, and cancer mortality were assessed by multiple Cox regression.
  
  
  RESULTS
  Clear dose-response relationships with respect to current and lifetime smoking intensity were consistently observed for methylation at six of the nine CpGs. Seven of the nine CpGs were also associated with mortality outcomes to various extents. A methylation score based on the top two CpGs (cg05575921 and cg06126421) showed the strongest associations with all-cause, cardiovascular, and cancer mortality, with adjusted hazard ratios (95% CI) of 3.59 (2.10, 6.16), 7.41 (2.81, 19.54), and 2.48 (1.01, 6.08), respectively, for participants with methylation levels in the lowest quartile at both CpGs. Adding methylation at those two CpGs into a model that included the variables of the Systematic Coronary Risk Evaluation chart for fatal cardiovascular risk prediction improved the predictive discrimination.
  
  
  CONCLUSIONS
  The novel methylation biomarkers are highly informative for both smoking exposure and smoking-related mortality outcomes. In particular, these biomarkers may substantially improve cardiovascular risk prediction. Nevertheless, the findings of the present study need to be further validated in additional large longitudinal studies.
  
  
  BACKGROUND
  Zhang Y, Schöttker B, Florath I, Stock C, Butterbach K, Holleczek B, Mons U, Brenner H. 2016. Smoking-associated DNA methylation biomarkers and their predictive value for all-cause and cardiovascular mortality. Environ Health Perspect 124:67-74; http://dx.doi.org/10.1289/ehp.1409020.
authors.affiliation: Division of Clinical Epidemiology and Aging Research, German Cancer Research Center, Heidelberg, Germany.
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhang
authors.forename: Ben
authors.initials: B
authors.lastname: Schöttker
authors.forename: Ines
authors.initials: I
authors.lastname: Florath
authors.forename: Christian
authors.initials: C
authors.lastname: Stock
authors.forename: Katja
authors.initials: K
authors.lastname: Butterbach
authors.forename: Bernd
authors.initials: B
authors.lastname: Holleczek
authors.forename: Ute
authors.initials: U
authors.lastname: Mons
authors.forename: Hermann
authors.initials: H
authors.lastname: Brenner
mesh_terms: D000368:Aged; D015415:Biomarkers / Q000097:blood*; D002318:Cardiovascular Diseases / Q000097:blood / Q000401:mortality; D019175:DNA Methylation / Q000187:drug effects*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012907:Smoking / Q000009:adverse effects*
chemical_list: D015415:Biomarkers