title: The effect of comorbidities upon ocular and systemic health-related quality of life.
abstract: OBJECTIVE
  The purpose of the study was to assess whether, and to what degree, comorbidities affect patient quality of life.
  
  
  METHODS
  A cross-sectional, quality-of-life study of 170 consecutive vitreoretinal patients compared the utility associated with a participant's primary (most incapacitating) disease and the utility associated with a grouping of all of the participants' diseases. The ocular diseases present included diabetic retinopathy (44%), macular degeneration (30%), lattice degeneration/retinal tear (14%), retinal vascular obstruction (5%), uveitis, macular oedema, macular pucker (5%) and others (2%). Participants underwent interviewer-administered, time trade-off utility questions for each disease, then for a compilation of all diseases. Their primary disease was defined by the lowest utility reported for a single disease, while other health conditions were considered comorbidities. A two-tailed, paired t test was used to compare the means of the primary disease utilities and compilation utilities. The study was powered to have a 90% chance of detecting an 8% difference in mean utility between the two utility groups
  
  
  RESULTS
  The mean lowest utility for the most disabling single health condition (primary disease) was 0.82 (SD 0.22; 95% CI 0.79 to 0.85. The mean utility for the grouping together of all diseases was 0.80 (SD 0.24, 95% CI 0.76 to 0.84). No significant difference was found between the mean utilities of the two groups (p = 0.56).
  
  
  CONCLUSIONS
  The overall health-related quality of life of a patient in an ophthalmic population with serious diseases appears to be primarily determined by the single disease that most adversely affects the individual's quality of life. This conclusion has significant implications in clinical care and when considering the use of comorbidities in cost-utility analyses.
authors.affiliation: Center for Value-Based Medicine, Flourtown, PA 19031, USA.
authors.forename: F J
authors.initials: FJ
authors.lastname: Real
authors.forename: G C
authors.initials: GC
authors.lastname: Brown
authors.forename: H C
authors.initials: HC
authors.lastname: Brown
authors.forename: M M
authors.initials: MM
authors.lastname: Brown
mesh_terms: D000368:Aged; D015897:Comorbidity; D005260:Female; D006304:Health Status; D006306:Health Surveys; D006801:Humans; D008297:Male; D008875:Middle Aged; D011788:Quality of Life; D012164:Retinal Diseases / Q000523:psychology*; D018434:Sickness Impact Profile