A challenge to the cross-cultural validity of the SF-36 health survey: factor structure in M ori, Pacific and New Zealand European ethnic groups

This paper reports on a principal component factor analysis of the SF-36 health status questionnaire in the three major ethnic groups in New Zealand (New Zealand Europeans, M ori and Pacific). The SF-36 is hypothesised to have a two-dimensional structure with distinct (weakly correlated) mental and physical health components, and support for this structural model has generally been found cross-nationally. However, in M ori and Pacific models of health mental and physical dimensions are not generally seen as separable, or independently functioning. This raises the possibility that the questionnaire’s hypothesised structural model would not be supported among M ori and Pacific ethnic groups. This study evaluated that possibility. The results of the analysis showed a similar factor structure among New Zealand Europeans, and younger M ori (<45 years) to that reported by Ware et al. for Western European countries. Among Pacific people and older M ori (45 years and over), however, the factor structure did not clearly differentiate physical and mental health components. Implications are discussed both specific to the SF-36 (and in particular the use of principal component summary scores), and more generally for the cross-cultural validity of self-reported health status measures.