Health status and healthy life measures for population health need assessment: modelling variability and uncertainty.

It is increasingly recognised that population health need assessments based on the comparison of clinical or demographic end points (e.g. area mortality rates) neglect population variation in broader aspects of health status and health-related quality of life. Similarly, outcome measures which neglect impacts on health-related quality of life may be an inadequate basis for assessing the effectiveness of health interventions. This paper reviews issues in assessing needs and outcomes at population level based on health status valuations. It considers especially the modelling of sources of uncertainty in measures of health status by using Bayesian sampling estimation methods which produce a distribution of summary outcome measures. The modelling issues are illustrated in models for individual level health status from survey responses and their incorporation in area life tables to derive total and healthy life expectancies. In particular, a health status index derived from Short Form 36 profile responses in a health and lifestyle survey in a London health authority provides a case study of community health needs assessment.