title: Obesity and quality of life: mediating effects of pain and comorbidities.
abstract: OBJECTIVE
  To estimate the association between body mass index (BMI) and health-related quality of life (HRQL) and examine whether joint pain and obesity-related comorbidities mediate the BMI-HRQL association.
  
  
  METHODS
  Population-based survey data from the 1999 Behavioral Risk Factor Surveillance Survey. Adults (N = 155,989) were classified according to BMI as underweight (<18.5 kg/m(2)), desirable weight (18.5 to 24.9 kg/m(2)), overweight (25 to 29.9 kg/m(2)), obese class I (30 to 34.9 kg/m(2)), obese class II (35 to 39.9 kg/m(2)), and obese class III (>/=40 kg/m(2)). Data including general health status, unhealthy days in the past 30 caused by physical problems and mental problems, and total unhealthy days in the past 30 were collected.
  
  
  RESULTS
  After adjusting for age, sex, race, smoking, education, and income, we observed J-shaped associations between BMI and HRQL. Compared with desirable weight adults, underweight, overweight, and obesity classes I, II, and III adults [odds ratio (OR) = 1.57, 1.19, 1.95, 2.72, and 4.36, respectively] were significantly (p < 0.001) more likely to report fair/poor general health status. For unhealthy days caused by physical problems, the corresponding ORs were 1.51, 1.15, 1.66, 2.27, and 3.61 (p < 0.001). For unhealthy days caused by mental problems, the ORs were 1.35, 1.14 1.43, 1.57, and 2.25 (p < 0.001). For total unhealthy days, the corresponding ORs were 1.27, 1.09, 1.37, 1.73, and 2.46 (p < 0.01). Adding joint pain and obesity-related comorbidities into models attenuated BMI-HRQL associations.
  
  
  CONCLUSIONS
  Associations between BMI and HRQL indices were J-shaped. Joint pain and comorbidities may mediate BMI-HRQL associations.
authors.affiliation: Obesity Research Center, St. Luke's/Roosevelt Hospital Center, Columbia University College of Physicians, New York, New York, USA.
authors.forename: Moonseong
authors.initials: M
authors.lastname: Heo
authors.forename: David B
authors.initials: DB
authors.lastname: Allison
authors.forename: Myles S
authors.initials: MS
authors.lastname: Faith
authors.forename: Shankuan
authors.initials: S
authors.lastname: Zhu
authors.forename: Kevin R
authors.initials: KR
authors.lastname: Fontaine
mesh_terms: D000328:Adult; D018771:Arthralgia / Q000453:epidemiology; D015992:Body Mass Index; D005260:Female; D006304:Health Status; D006801:Humans; D016015:Logistic Models; D008297:Male; D001523:Mental Disorders / Q000453:epidemiology; D008875:Middle Aged; D009017:Morbidity; D009765:Obesity / Q000453:epidemiology / Q000503:physiopathology*; D016017:Odds Ratio; D010146:Pain; D011788:Quality of Life