title: Obesity/overweight reduces the risk of active tuberculosis: a nationwide population-based cohort study in Taiwan.
abstract: Obesity affects immune function by increasing the number of T helper lymphocytes, which may reduce the risk of tuberculosis (TB) infection. However, the effect of obesity on TB development has not been extensively studied. This nationwide population-based cohort study investigated the effect of obesity on TB development in Taiwanese adults.
  
  
  
  We included 46 028 adult participants (age ⩾18 years) from three rounds (2001, 2005 and 2009) of the Taiwan National Health Interview Survey. Obesity and overweight were defined as a body mass index (BMI) ⩾27 and 24-26.9 (kg/m2), respectively. Data on BMI and other covariates at baseline were collected by in-person interviews. Incident cases of active TB were identified from the National Health Insurance database. Multivariable logistic regression was used to estimate the associations of obesity and overweight with active TB, with adjustment for age, sex, smoking, alcohol consumption, socioeconomic status and other covariates.
  
  
  
  In total, 241 new cases of active TB occurred during the study period. Obesity (adjusted odds ratio [AOR], 0.43; 95% confident interval [CI], 0.28-0.67) and overweight (AOR, 0.67; 95% CI, 0.49-0.91) were associated with lower risk of incident TB, after adjusting for demographic characteristics and comorbidities. There was a linear dose-response relation of BMI with active TB incidence (AOR per unit change in BMI, 0.92; 95% CI, 0.88-0.95; P <0.001).
  
  
  
  Obesity and overweight are associated with lower risk of active TB. Future studies should investigate the underlying mechanisms and clinical and epidemiological consequences of these findings.
authors.affiliation: Section of Infectious Diseases, Taipei City Hospital, Taipei City Government, Taipei, Taiwan.|School of Medicine, National Yang-Ming University, Taipei, Taiwan.|Department of Health and Welfare, College of City Management, University of Taipei, Taipei, Taiwan.
authors.forename: Y-F
authors.initials: YF
authors.lastname: Yen
authors.affiliation: Department of Education and Research, Taipei City Hospital, Taipei, Taiwan.|Institute of Public Health, National Yang-Ming University, Taipei, Taiwan.
authors.forename: H-Y
authors.initials: HY
authors.lastname: Hu
authors.affiliation: Department of Dentistry, Taipei City Hospital, Taipei, Taiwan.|School of Dentistry, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Y-L
authors.initials: YL
authors.lastname: Lee
authors.affiliation: Graduate Institute of Sports and Health, National Changhua University of Education, Changhua, Taiwan.
authors.forename: P-W
authors.initials: PW
authors.lastname: Ku
authors.affiliation: Institute of Public Health, National Yang-Ming University, Taipei, Taiwan.
authors.forename: I-F
authors.initials: IF
authors.lastname: Lin
authors.affiliation: School of Medicine, National Yang-Ming University, Taipei, Taiwan.|Department of Neurosurgery, Taipei City Hospital, Taipei, Taiwan.|Department of Health Care Management, National Taipei University of Nursing and Health Sciences, Taipei, Taiwan.
authors.forename: D
authors.initials: D
authors.lastname: Chu
authors.affiliation: School of Medicine, National Yang-Ming University, Taipei, Taiwan.|Division of Endocrinology and Metabolism, Department of Internal Medicine, Puli Branch of Taichung Veterans General Hospital, Nantou, Taiwan.|Department of Exercise Health Science, National Taiwan University of Sport, Taichung, Taiwan.
authors.forename: Y-J
authors.initials: YJ
authors.lastname: Lai
mesh_terms: D000328:Adult; D015992:Body Mass Index; D016516:CD4-CD8 Ratio; D015897:Comorbidity; D003430:Cross-Sectional Studies; D005260:Female; D006306:Health Surveys; D006801:Humans; D020738:Leptin / Q000378:metabolism; D008213:Lymphocyte Activation; D008297:Male; D008875:Middle Aged; D050177:Overweight / Q000453:epidemiology / Q000276:immunology* / Q000503:physiopathology; D012307:Risk Factors; D013601:T-Lymphocytes / Q000276:immunology; D013624:Taiwan / Q000453:epidemiology; D013851:Thinness / Q000453:epidemiology / Q000276:immunology* / Q000503:physiopathology; D014376:Tuberculosis / Q000453:epidemiology / Q000276:immunology* / Q000503:physiopathology
chemical_list: D020738:Leptin