title: Association between class III obesity (BMI of 40-59 kg/m2) and mortality: a pooled analysis of 20 prospective studies.
abstract: BACKGROUND
  The prevalence of class III obesity (body mass index [BMI]≥40 kg/m2) has increased dramatically in several countries and currently affects 6% of adults in the US, with uncertain impact on the risks of illness and death. Using data from a large pooled study, we evaluated the risk of death, overall and due to a wide range of causes, and years of life expectancy lost associated with class III obesity.
  
  
  RESULTS
  In a pooled analysis of 20 prospective studies from the United States, Sweden, and Australia, we estimated sex- and age-adjusted total and cause-specific mortality rates (deaths per 100,000 persons per year) and multivariable-adjusted hazard ratios for adults, aged 19-83 y at baseline, classified as obese class III (BMI 40.0-59.9 kg/m2) compared with those classified as normal weight (BMI 18.5-24.9 kg/m2). Participants reporting ever smoking cigarettes or a history of chronic disease (heart disease, cancer, stroke, or emphysema) on baseline questionnaires were excluded. Among 9,564 class III obesity participants, mortality rates were 856.0 in men and 663.0 in women during the study period (1976-2009). Among 304,011 normal-weight participants, rates were 346.7 and 280.5 in men and women, respectively. Deaths from heart disease contributed largely to the excess rates in the class III obesity group (rate differences = 238.9 and 132.8 in men and women, respectively), followed by deaths from cancer (rate differences = 36.7 and 62.3 in men and women, respectively) and diabetes (rate differences = 51.2 and 29.2 in men and women, respectively). Within the class III obesity range, multivariable-adjusted hazard ratios for total deaths and deaths due to heart disease, cancer, diabetes, nephritis/nephrotic syndrome/nephrosis, chronic lower respiratory disease, and influenza/pneumonia increased with increasing BMI. Compared with normal-weight BMI, a BMI of 40-44.9, 45-49.9, 50-54.9, and 55-59.9 kg/m2 was associated with an estimated 6.5 (95% CI: 5.7-7.3), 8.9 (95% CI: 7.4-10.4), 9.8 (95% CI: 7.4-12.2), and 13.7 (95% CI: 10.5-16.9) y of life lost. A limitation was that BMI was mainly ascertained by self-report.
  
  
  CONCLUSIONS
  Class III obesity is associated with substantially elevated rates of total mortality, with most of the excess deaths due to heart disease, cancer, and diabetes, and major reductions in life expectancy compared with normal weight. Please see later in the article for the Editors' Summary.
authors.affiliation: Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, Maryland, United States of America.
authors.forename: Cari M
authors.initials: CM
authors.lastname: Kitahara
authors.affiliation: Department of Nutrition, Harvard School of Public Health, Boston, Massachusetts, United States of America; Department of Epidemiology, Harvard School of Public Health, Boston, Massachusetts, United States of America.
authors.forename: Alan J
authors.initials: AJ
authors.lastname: Flint
authors.affiliation: Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, Maryland, United States of America.
authors.forename: Amy
authors.initials: A
authors.lastname: Berrington de Gonzalez
authors.affiliation: Division of Cancer Etiology, Department of Population Sciences, Beckman Research Institute, City of Hope, Duarte, California, United States of America.
authors.forename: Leslie
authors.initials: L
authors.lastname: Bernstein
authors.affiliation: Westat, Rockville, Maryland, United States of America.
authors.forename: Michelle
authors.initials: M
authors.lastname: Brotzman
authors.affiliation: Cancer Epidemiology Centre, Cancer Council of Victoria, Melbourne, Australia; Centre for Molecular, Environmental, Genetic, and Analytic Epidemiology, University of Melbourne, Melbourne, Australia.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: MacInnis
authors.affiliation: Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, Maryland, United States of America.
authors.forename: Steven C
authors.initials: SC
authors.lastname: Moore
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health and Health Services, George Washington University, Washington, District of Columbia, United States of America.
authors.forename: Kim
authors.initials: K
authors.lastname: Robien
authors.affiliation: Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, Maryland, United States of America.
authors.forename: Philip S
authors.initials: PS
authors.lastname: Rosenberg
authors.affiliation: Center for Health Research, School of Public Health, Loma Linda University, Loma Linda, California, United States of America.
authors.forename: Pramil N
authors.initials: PN
authors.lastname: Singh
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden; Department of Community Medicine, Faculty of Health Sciences, University of Tromsø-The Arctic University of Norway, Tromsø, Norway; Department of Research, Cancer Registry of Norway, Oslo, Norway; Samfundet Folkhälsan, Helsinki, Finland.
authors.forename: Elisabete
authors.initials: E
authors.lastname: Weiderpass
authors.affiliation: Department of Epidemiology, Harvard School of Public Health, Boston, Massachusetts, United States of America; Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Hans Olov
authors.initials: HO
authors.lastname: Adami
authors.affiliation: Department of Epidemiology, School of Medicine, University of California, Irvine, California, United States of America.
authors.forename: Hoda
authors.initials: H
authors.lastname: Anton-Culver
authors.affiliation: Division of Cancer Control and Population Sciences, National Cancer Institute, Bethesda, Maryland, United States of America.
authors.forename: Rachel
authors.initials: R
authors.lastname: Ballard-Barbash
authors.affiliation: Divisions of Preventive Medicine and Aging, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America.
authors.forename: Julie E
authors.initials: JE
authors.lastname: Buring
authors.affiliation: Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, Maryland, United States of America.
authors.forename: D Michal
authors.initials: DM
authors.lastname: Freedman
authors.affiliation: Department of Epidemiology, Biostatistics, and Population Medicine, Loma Linda University School of Public Health, Loma Linda, California, United States of America.
authors.forename: Gary E
authors.initials: GE
authors.lastname: Fraser
authors.affiliation: Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, Maryland, United States of America.
authors.forename: Laura E
authors.initials: LE
authors.lastname: Beane Freeman
authors.affiliation: Epidemiology Research Program, American Cancer Society, Atlanta, Georgia, United States of America.
authors.forename: Susan M
authors.initials: SM
authors.lastname: Gapstur
authors.affiliation: Divisions of Preventive Medicine and Aging, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America; Massachusetts Veteran's Epidemiology, Research and Information Center, Geriatric Research Education and Clinical Center, VA Boston Healthcare System, Boston, Massachusetts, United States of America.
authors.forename: John Michael
authors.initials: JM
authors.lastname: Gaziano
authors.affiliation: Cancer Epidemiology Centre, Cancer Council of Victoria, Melbourne, Australia; Centre for Molecular, Environmental, Genetic, and Analytic Epidemiology, University of Melbourne, Melbourne, Australia.
authors.forename: Graham G
authors.initials: GG
authors.lastname: Giles
authors.affiliation: Division of Nutritional Epidemiology, National Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Niclas
authors.initials: N
authors.lastname: Håkansson
authors.affiliation: Epidemiology Branch, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, North Carolina, United States of America.
authors.forename: Jane A
authors.initials: JA
authors.lastname: Hoppin
authors.affiliation: Department of Nutrition, Harvard School of Public Health, Boston, Massachusetts, United States of America; Department of Epidemiology, Harvard School of Public Health, Boston, Massachusetts, United States of America.
authors.forename: Frank B
authors.initials: FB
authors.lastname: Hu
authors.affiliation: Division of Epidemiology, Department of Population Health and NYU Cancer Institute, NYU School of Medicine, New York, New York, United States of America.
authors.forename: Karen
authors.initials: K
authors.lastname: Koenig
authors.affiliation: Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, Maryland, United States of America.
authors.forename: Martha S
authors.initials: MS
authors.lastname: Linet
authors.affiliation: Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, Maryland, United States of America.
authors.forename: Yikyung
authors.initials: Y
authors.lastname: Park
authors.affiliation: Epidemiology Research Program, American Cancer Society, Atlanta, Georgia, United States of America.
authors.forename: Alpa V
authors.initials: AV
authors.lastname: Patel
authors.affiliation: Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, Maryland, United States of America.
authors.forename: Mark P
authors.initials: MP
authors.lastname: Purdue
authors.affiliation: Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, Maryland, United States of America.
authors.forename: Catherine
authors.initials: C
authors.lastname: Schairer
authors.affiliation: Divisions of Preventive Medicine and Aging, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America.
authors.forename: Howard D
authors.initials: HD
authors.lastname: Sesso
authors.affiliation: Johns Hopkins Sidney Kimmel Comprehensive Cancer Center, Baltimore, Maryland, United States of America; Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, United States of America.
authors.forename: Kala
authors.initials: K
authors.lastname: Visvanathan
authors.affiliation: Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America.
authors.forename: Emily
authors.initials: E
authors.lastname: White
authors.affiliation: Division of Nutritional Epidemiology, National Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Alicja
authors.initials: A
authors.lastname: Wolk
authors.affiliation: Division of Epidemiology, Department of Population Health and NYU Cancer Institute, NYU School of Medicine, New York, New York, United States of America.
authors.forename: Anne
authors.initials: A
authors.lastname: Zeleniuch-Jacquotte
authors.affiliation: Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, Maryland, United States of America.
authors.forename: Patricia
authors.initials: P
authors.lastname: Hartge
mesh_terms: D001315:Australia / Q000453:epidemiology; D015992:Body Mass Index; D006801:Humans; D008017:Life Expectancy; D009765:Obesity / Q000401:mortality*; D011446:Prospective Studies; D012307:Risk Factors; D013548:Sweden / Q000453:epidemiology; D014481:United States / Q000453:epidemiology