Measuring physical and mental health using the SF-12: implications for community surveys of mental health.
OBJECTIVE
The effects of using different approaches to scoring the SF-12 summary scales of physical and mental health were examined with a view to informing the design and interpretation of community-based survey research.


METHODS
Data from a population-based study of 7485 participants in three cohorts aged 20-24, 40-44 and 60-64 years were used to examine relationships among measures of physical and mental health calculated from the same items using the SF-12 and RAND-12 approaches to scoring, and other measures of chronic physical conditions and psychological distress.


RESULTS
A measure of physical health constructed using the RAND-12 scoring showed a monotonic negative association with psychological distress as measured by the Goldberg depression and anxiety scales. However, a non-monotonic association was evident in the relationship between SF-12 physical health scores and distress, with very high SF-12 physical health scores corresponding with high levels of distress. These relationships highlight difficulties in interpretation that can arise when using the SF-12 summary scales in some analytical contexts.


CONCLUSIONS
It is recommended that community surveys that measure physical and mental functioning using the SF-12 items generate summary scores using the RAND-12 protocol in addition to the SF-12 approach. In general, researchers should be wary of using factor scores based on orthogonal rotation, which assumes that measures are uncorrelated, to represent constructs that have an actual association.
Windsor
Timothy D
TD
Centre for Mental Health Research, Australian National University, Canberra, Australian Capital Territory 0200, Australia. tim.windsor@anu.edu.au
Rodgers
Bryan
B
Butterworth
Peter
P
Anstey
Kaarin J
KJ
Jorm
Anthony F
AF
D000328:Adult; D000367:Age Factors; D003625:Data Collection; D005163:Factor Analysis, Statistical; D005260:Female; D006305:Health Status Indicators; D006801:Humans; D008297:Male; D008603:Mental Health / Q000706:statistics & numerical data*; D008875:Middle Aged; D011594:Psychometrics; D015203:Reproducibility of Results; D018434:Sickness Impact Profile; D013223:Statistics as Topic; D011795:Surveys and Questionnaires