Slade GD*, Spencer AJ, Roberts-Thomson K, Chalmers J, Carter KD

Cross-sectional studies of nationally-representative samples have found fewer adverse impacts on health related quality of life (HRQoL) reported by people aged 70+ years compared with people aged 60-69 years, a result consistent with an ageing effect of increasing resilience and/or resignation. However, differences observed in cross-sectional studies may also be due to cohort or period effects. Objectives: To determine if adverse impacts on HRQoL among two age groups of elderly, dentate South Australians changed over an 11 period. Methods: Prospective cohort study of people aged 60+ years at baseline who were representative of the populations of Adelaide and Mt Gambier. At baseline in 1991/92, 902 dentate subjects completed a 49-item Oral Health Impact Profile (OHIP) questionnaire that asked about adverse impacts of oral conditions on quality of life. OHIP questionnaires were re-administered to n=257 dentate people who remained in the study 11years after recruitment. Each subject's summed, weighted OHIP score was calculated (Slade and Spencer, Community Dental Health 1994;11:3-11) and person-level change over 11 years was computed. Differences at baseline and over 11 years were compared between two age groups and evaluated statistically using t-tests. Results: At baseline, the mean (+/- se) OHIP score was 16% lower for people aged 70+ years (26.8 +/- 1.4) compared with 60-69 yr olds (31.9 +/- 1.6) - t-test P=0.01. However, OHIP scores remained virtually identical after 11 years of follow-up for people aged 60-69 years at baseline (29.5 +/- 2.4, paired t-test P=0.59) and increased marginally for those aged 70+ (31.5 +/- 4.1, paired t-test, P=0.24). Conclusion: Stability of OHIP scores observed over 11 years demonstrates a lack of ageing or period effects. Cross-sectional differences observed in OHIP scores between age groups at baseline can best be explained by cohort differences in this population of elderly South Australians. Supported by NHMRC, NIH DE-09588.