title: Gender-specific association between tobacco smoking and central obesity among 0.5 million Chinese people: the China Kadoorie Biobank Study.
abstract: OBJECTIVE
  Lifestyle factors are well-known important modifiable risk factors for obesity; the association between tobacco smoking and central obesity, however, is largely unknown in the Chinese population. This study examined the relationship between smoking and central obesity in 0.5 million Chinese adults, a population with a low prevalence of general obesity, but a high prevalence of central obesity.
  
  
  METHODS
  A total of 487,527 adults (200,564 males and 286,963 females), aged 30-79 years, were enrolled in the baseline survey of the China Kadoorie Biobank (CKB) Study conducted during 2004-2008. Waist circumference (WC) and WC/height ratio (WHtR) were used as measures of central obesity.
  
  
  RESULTS
  The prevalence of regular smokers was significantly higher among males (60.6%) than among females (2.2%). The prevalence of central obesity increased with age and BMI levels, with a significant gender difference (females>males). Of note, almost all obese adults (99.4%) were centrally obese regardless of gender. In multivariable regression analyses, adjusting for age, education, physical activity, alcohol use and survey site, regular smoking was inversely associated with BMI in males (standardized regression coefficients, β= -0.093, p<0.001) and females (β= -0.025, p<0.001). Of interest, in the BMI stratification analyses in 18 groups, all βs of regular smoking for WHtR were positive in both genders; the βs showed a significantly greater increasing trend with increasing BMI in males than in females. In the analyses with model adjustment for BMI, the positive associations between regular smoking and WHtR were stronger in males (β= 0.021, p<0.001) than in females (β= 0.008, p<0.001) (p<0.001 for gender difference). WC showed considerably consistent results.
  
  
  CONCLUSIONS
  The data indicate that tobacco smoking is an important risk factor for central obesity, but the association is gender-specific and depends on the adjustment for general obesity.
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Peking University Health Science Center, Beijing, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Lv
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Peking University Health Science Center, Beijing, China; Department of Epidemiology, School of Public Health and Tropical Medicine, Tulane University, New Orleans, Louisiana, United States of America.
authors.forename: Wei
authors.initials: W
authors.lastname: Chen
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Peking University Health Science Center, Beijing, China; Department of Epidemiology, School of Public Health and Tropical Medicine, Tulane University, New Orleans, Louisiana, United States of America.
authors.forename: Dianjianyi
authors.initials: D
authors.lastname: Sun
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Peking University Health Science Center, Beijing, China; Department of Epidemiology, School of Public Health and Tropical Medicine, Tulane University, New Orleans, Louisiana, United States of America.
authors.forename: Shengxu
authors.initials: S
authors.lastname: Li
authors.affiliation: Clinical Trial Service Unit & Epidemiological Studies Unit (CTSU), Nuffield Department of Population Health, University of Oxford, United Kingdom.
authors.forename: Iona Y
authors.initials: IY
authors.lastname: Millwood
authors.affiliation: Clinical Trial Service Unit & Epidemiological Studies Unit (CTSU), Nuffield Department of Population Health, University of Oxford, United Kingdom.
authors.forename: Margaret
authors.initials: M
authors.lastname: Smith
authors.affiliation: Chinese Academy of Medical Sciences, Beijing, China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Guo
authors.affiliation: Chinese Academy of Medical Sciences, Beijing, China.
authors.forename: Zheng
authors.initials: Z
authors.lastname: Bian
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Peking University Health Science Center, Beijing, China.
authors.forename: Canqing
authors.initials: C
authors.lastname: Yu
authors.affiliation: Chinese Academy of Medical Sciences, Beijing, China.
authors.forename: Huiyan
authors.initials: H
authors.lastname: Zhou
authors.affiliation: Chinese Academy of Medical Sciences, Beijing, China.
authors.forename: Yunlong
authors.initials: Y
authors.lastname: Tan
authors.affiliation: China National Center for Food Safety Risk Assessment, Beijing, China.
authors.forename: Junshi
authors.initials: J
authors.lastname: Chen
authors.affiliation: Clinical Trial Service Unit & Epidemiological Studies Unit (CTSU), Nuffield Department of Population Health, University of Oxford, United Kingdom.
authors.forename: Zhengming
authors.initials: Z
authors.lastname: Chen
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Peking University Health Science Center, Beijing, China; Chinese Academy of Medical Sciences, Beijing, China.
authors.forename: Liming
authors.initials: L
authors.lastname: Li
mesh_terms: D000328:Adult; D000368:Aged; D018070:Biological Specimen Banks; D015992:Body Mass Index; D002681:China / Q000453:epidemiology; D004522:Educational Status; D005260:Female; D006306:Health Surveys; D006801:Humans; D008297:Male; D008875:Middle Aged; D009043:Motor Activity; D056128:Obesity, Abdominal / Q000453:epidemiology* / Q000503:physiopathology; D015995:Prevalence; D012044:Regression Analysis; D012307:Risk Factors; D012737:Sex Factors; D012907:Smoking / Q000453:epidemiology* / Q000503:physiopathology; D055105:Waist Circumference; D065927:Waist-Height Ratio