title: Greater Coronary Heart Disease Risk With Lower Intensity and Longer Duration Smoking Compared With Higher Intensity and Shorter Duration Smoking: Congruent Results Across Diverse Cohorts.
abstract: BACKGROUND
  Relative risks (RRs) for coronary heart disease (CHD) by cigarettes/day exhibit a concave pattern, implying the RR increase with each additional cigarette/day consumed decreases with greater intensity. Interpreting this pattern faces limitations, since cigarettes/day alone does not fully characterize smoking-related exposure. A more complete understanding of smoking and CHD risk requires a more comprehensive representation of smoking.
  
  
  METHODS
  Using Poisson regression, we applied a RR model in pack-years and cigarettes/day to analyze two diverse cohorts, the US Agricultural Health Study, with 4396 CHD events and 1 425 976 person-years of follow-up, and the Finnish Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study, with 5979 CHD events and 486 643 person-years.
  
  
  RESULTS
  In both cohorts, the concave RR pattern with cigarettes/day was consistent with cigarettes/day modifying a linear RR association for CHD by pack-years within categories of cigarettes/day, indicating that strength of the pack-years association depended on cigarettes/day (p < .01). For example, at 50 pack-years (365 000 total cigarettes), estimated RRs of CHD were 2.1 for accrual at 20 cigarettes/day and 1.5 for accrual at 50 cigarettes/day.
  
  
  CONCLUSIONS
  RRs for CHD increased with pack-years with smoking intensities affecting the strength of association. For equal pack-years, smoking fewer cigarettes/day for longer duration was more deleterious than smoking more cigarettes/day for shorter duration. We have now observed inverse smoking intensity effects in multiple cohorts with differing smoking patterns and other characteristics, suggesting a common underlying phenomenon.
  
  
  CONCLUSIONS
  Risk of CHD increases with pack-years of smoking, but accrual intensity strongly influences the strength of the association, such that smoking fewer cigarettes/day for longer duration is more deleterious than smoking more cigarettes/day for shorter duration. This observation offers clues to better understanding biological mechanisms, and reinforces the importance of cessation rather than smoking less to reduce CHD risk.
authors.affiliation: Biostatistics Branch, Division of Cancer Epidemiology and Genetics, US National Cancer Institute, National Institutes of Health, Bethesda, MD.
authors.forename: Jay H
authors.initials: JH
authors.lastname: Lubin
authors.affiliation: Metabolic Epidemiology Branch, Division of Cancer Epidemiology and Genetics, US National Cancer Institute, National Institutes of Health, Bethesda, MD.
authors.forename: Demetrius
authors.initials: D
authors.lastname: Albanes
authors.affiliation: Department of Biological Sciences and Center for Human Health and the Environment, North Carolina State University, Raleigh, NC.
authors.forename: Jane A
authors.initials: JA
authors.lastname: Hoppin
authors.affiliation: Epidemiology Branch, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, Durham, NC.
authors.forename: Honglei
authors.initials: H
authors.lastname: Chen
authors.affiliation: Occupational and Environmental Epidemiology Branch, Division of Cancer Epidemiology and Genetics, US National Cancer Institute, National Institutes of Health, Bethesda, MD.
authors.forename: Catherine C
authors.initials: CC
authors.lastname: Lerro
authors.affiliation: Metabolic Epidemiology Branch, Division of Cancer Epidemiology and Genetics, US National Cancer Institute, National Institutes of Health, Bethesda, MD.
authors.forename: Stephanie J
authors.initials: SJ
authors.lastname: Weinstein
authors.affiliation: Epidemiology Branch, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, Durham, NC.
authors.forename: Dale P
authors.initials: DP
authors.lastname: Sandler
authors.affiliation: Occupational and Environmental Epidemiology Branch, Division of Cancer Epidemiology and Genetics, US National Cancer Institute, National Institutes of Health, Bethesda, MD.
authors.forename: Laura E
authors.initials: LE
authors.lastname: Beane Freeman
mesh_terms: D000368:Aged; D015331:Cohort Studies; D003327:Coronary Disease / Q000453:epidemiology* / Q000401:mortality; D004311:Double-Blind Method; D005387:Finland / Q000453:epidemiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D012907:Smoking / Q000453:epidemiology*; D016540:Smoking Cessation / Q000379:methods*; D013997:Time Factors; D062789:Tobacco Products / Q000706:statistics & numerical data*