Joint modelling of the morbidity and mortality impacts of air pollution control: QALYs versus MILYs

Abstract:

Background: Existing attempts to model the morbidity and mortality impacts of air pollution, in particular the “Morbidity Inclusive Life Year” (MILY) used in a 2006 report by the US Environmental Protection Agency, have failed adequately to account for the inter-relationships between mortality and morbidity. This leads to over-estimation of morbidity impacts for some individuals' and under-estimation for others, and means that environmental health policymakers are using health impact estimates that are not comparable with QALY-based estimates in other policy sectors such as healthcare and public health.

Objectives: To develop and populate a Markov model that allows joint evaluation of the inter-related morbidity and mortality impacts of long-term air pollution exposure in a consistent QALY-based framework, alongside heath care resource use. To apply the model to assess a hypothetical intervention that reduces PM_2.5 concentrations by 1 mg/m³ on the current adult population (40+) of Greater London and England and Wales.

Method: A Markov model was constructed that encompassed the three chronic disease pathways on which there is relatively solid epidemiological evidence of air pollution impact: chronic obstructive pulmonary disease, coronary heart disease and lung cancer. As part of model parametrisation, systematic reviews and meta-analyses of risk estimates of dying from all-causes and dying from lung-cancer were performed. Uncertainty in the model’s key parameters was handled probabilistically. 

Preliminary Results: Preliminary results will be presented at the seminar, including breakdowns of QALY gains and healthcare cost savings by age and gender.