The effect of comorbidities upon ocular and systemic health-related quality of life

Aim: 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.