title: Body mass index and future healthcare costs: a retrospective cohort study.
abstract: OBJECTIVE
  To assess the relationship between body mass index (BMI) and future healthcare costs.
  
  
  METHODS
  We undertook a retrospective cohort study of the relationship between obesity and future healthcare costs at Kaiser Permanente Northwest Division, a large health maintenance organization in Portland, Oregon. Study subjects (n = 1286) consisted of persons who responded to a 1990 health survey that was mailed to a random sample of adult Kaiser Permanente Northwest Division members who were 35 to 64 years of age; had a BMI > or = 20 kg/m(2) (based on self-reported height and weight); did not smoke cigarettes; and did not have a history of coronary heart disease, stroke, human immunodeficiency virus, or cancer. Subjects were stratified according to their BMI in 1990 (20 to 24.9, 25 to 29.9, and > or = 30 kg/m(2); n = 545, 474, and 367, respectively). We then tallied their costs (in 1998 US dollars) for all inpatient care, outpatient services, and prescription drugs over a 9-year period (1990 through 1998).
  
  
  RESULTS
  For persons with BMIs of 20 to 24.9 kg/m(2), mean (+/-SE) annual costs of prescription drugs, outpatient services, inpatient care, and all medical care averaged $261 (+/-18), $848 (+/-59), $532 (+/-85), and $1631 (+/-120), respectively, over the study period. Cost ratios (95% confidence intervals) for persons with BMIs of 25 to 29.9 kg/m(2) and > or = 30 kg/m(2), respectively, were 1.37 (1.12 to 1.66) and 2.05 (1.62 to 2.55) for prescription drugs, 0.96 (0.83 to 1.13) and 1.14 (0.97 to 1.37) for outpatient services, 1.20 (0.81 to 1.86) and 1.38 (0.91 to 2.14) for inpatient care, and 1.10 (0.91 to 1.35) and 1.36 (1.11 to 1.68) for all medical care.
  
  
  CONCLUSIONS
  Future healthcare costs are higher for persons who are overweight, especially those with BMIs > or = 30 kg/m(2).
authors.affiliation: Policy Analysis Inc. (PAI), Brookline, Massachusetts 02445, USA.
authors.forename: D
authors.initials: D
authors.lastname: Thompson
authors.forename: J B
authors.initials: JB
authors.lastname: Brown
authors.forename: G A
authors.initials: GA
authors.lastname: Nichols
authors.forename: P J
authors.initials: PJ
authors.lastname: Elmer
authors.forename: G
authors.initials: G
authors.lastname: Oster
mesh_terms: D000328:Adult; D000367:Age Factors; D015992:Body Mass Index; D015331:Cohort Studies; D003365:Costs and Cost Analysis; D005260:Female; D017048:Health Care Costs / Q000706:statistics & numerical data / Q000639:trends*; D006296:Health Services / Q000191:economics / Q000706:statistics & numerical data; D006760:Hospitalization / Q000191:economics / Q000706:statistics & numerical data; D006801:Humans; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000191:economics*; D012189:Retrospective Studies