Factor analytic study of two questionnaires measuring oral health-related quality of life among children and adults in New Zealand, Germany and Poland.

A questionnaire designed to measure oral health-related quality of life (OHRQOL) in adults and children was assessed for its factorial structure and reliability using data from the Second International Collaborative Study on Oral Health Outcomes in New Zealand, Poland and Germany. Principal component analysis with orthogonal and oblique rotation was applied. The three-factor structure hypothesized for the children's questionnaire (self-reported oral disease symptoms, perceived oral well-being, social and physical functioning) was confirmed in New Zealand and Poland, and two self-reported oral disease symptom dimensions emerged in Germany. Five factors instead of the three hypothesized were identified for adults: two dimensions of symptoms were identified, and social and physical functioning appeared to be independent dimensions of OHRQOL. Similarity between the factors was demonstrated in all three countries. The reliability of the questionnaire ranged from moderate to excellent depending on the dimension and the country. These findings provide preliminary evidence of the cross-cultural stability of the OHRQOL questionnaire in New Zealand, Poland and Germany, for both children and adults. Further investigations by the present authors of the properties of the instrument in other samples will focus on demonstrating the stability and replicability of the factor structure identified here.