Short Form 36 (SF-36) Health Survey questionnaire: which normative data should be used? Comparisons between the norms provided by the Omnibus Survey in Britain, the Health Survey for England and the Oxford Healthy Life Survey.

BACKGROUND: Population norms for the attributes included in measurement scales are required to provide a standard with which scores from other study populations can be compared. This study aimed to obtain population norms for the Short Form 36 (SF-36) Health Survey Questionnaire, derived from a random sample of the population in Britain who were interviewed at home, and to make comparisons with other commonly used norms.
METHODS: The method was a face-to-face interview survey of a random sample of 2056 adults living at home in Britain (response rate 78 per cent). Comparisons of the SF-36 scores derived from this sample were made with the Health Survey for England and the Oxford Healthy Life Survey.
RESULTS: Controlling for age and sex, many of mean scores on the SF-36 dimensions differed between the three datasets. The British interview sample had better total means for Physical Functioning, Social Functioning, Mental Health, Energy/Vitality, and General Health Perceptions. The Health (interview) Survey for England had the lowest (worst) total mean scores for Physical Functioning, Social Functioning, Role Limitations (physical), Bodily Pain, and Health Perceptions. The postal sample in central England had the lowest (worst) total mean scores for Role Limitations (emotional), Mental Health and Energy/Vitality.
CONCLUSION: Responses obtained from interview methods may suffer more from social desirability bias (resulting in inflated SF-36 scores) than postal surveys. Differences in SF-36 means between surveys are also likely to reflect question order and contextual effects of the questionnaires. This indicates the importance of providing mode-specific population norms for the various methods of questionnaire administration.