Objective: To examine the psychometric properties of a modified version of the index of Oral Impacts on Daily Performance (OIDP) in elderly populations in two European countries, namely Great Britain and Greece. The psychometric properties examined in this study refer to internal consistency and face, content, criterion and construct validity.
Design and setting: Cross-sectional epidemiologic surveys of independently living people aged 65 years or older. Data were collected by interviewers through structured questionnaires. The British sample consisted of the randomly selected independently living persons that participated in the dental component of the National Diet and Nutrition Survey (NDNS) of adults aged 65 years or over. The Greek sample is an opportunity sample drawn from eligible people living in two municipalities of the Athens region.
Subjects: 753 people participated in the British and 681 in the Greek sample.
Results: Through pilot work in both countries, the OIDP index was modified and both Greek and British modified versions demonstrated satisfactory face and content validity. In the main studies, Cronbach's alpha of the modified OIDP was 0.77 for the Greek and 0.69 for the British sample. In both samples, the index showed very significant associations with perceived dental treatment need (p<0.001), perceived general health (p<0.001 in Greek, p=0.002 in British) and intermediate oral impacts (p<0.001), as well as with satisfaction with oral health in the Greek sample (p<0.001).
Conclusions: Overall, this study has demonstrated that the modified OIDP is a valid and reliable measure of oral health related quality of life in elderly people in Great Britain and Greece.