ASSESSING CHANGE IN QUALITY-OF-LIFE USING THE ORAL-HEALTH-IMPACT-PROFILE

Traditionally, longitudinal studies of oral health have measured only disease progression and ignored improvements in health. Objectives: Th is study examines methodological issues that arise in longitudinal ass essment of change in oral health-related quality of life (OHRQOL). Met hods: Baseline and 2-year follow-up data were used from an observation al longitudinal study of 498 people aged 60 years or more living in So uth Australia. Oral health-related quality of life was measured using the Oral Health Impact Profile (OHIP). Three hypothesized risk predict ors (tooth loss, problem-based dental visits and financial hardship) w ere selected to examine the effects of four methods of measuring chang e: categorical measures of improvement, deterioration and net change, and a quantitative measure of net change in OHIP scores. Results: Some 31.7% of people experienced some improvement and 32.7% experienced so me deterioration in OHRQOL. All three high-risk groups had approximate ly twice the rate of deterioration in OHRQOL compared with their corre sponding low-risk groups. Surprisingly, high-risk groups also had high er rates of improvement. When measured categorically, these effects di d not cancel one another, indicating that improvement and deterioratio n in OHRQOL can be experienced simultaneously. However, quantitative a nalyses cause improvements and deteriorations to cancel, and analysis of mean OHIP scores created a spurious impression that change in OHRQO L did not differ between dental visit groups. Furthermore, changes in mean OHIP scores were masked by regression to the mean. Conclusions: O ral health-related quality of life measures capture both improvement a nd deterioration in health status, creating new complexities for conce ptualizing and analyzing change in longitudinal studies.