Conceptual models of the disablement process agree that disease or active pathology result in limitations of physical and mental function leading to disability. The major causes of disability in later life are known to be cardiovascular and cerebrovascular disease, vision and hearing problems, arthritis, dementia and depression. Despite this, projections of the future number of disabled older people have not taken into account how the disease patterns may change through new treatments or better or worse health behaviours. Moreover projections do not provide insight into the relationship between overall length of life and the time spent with disability, thereby addressing the important questions of whether there will be a compression or expansion of disability in the future.

Aims

The aim of this Work Package is to explore, through microsimulation, how changes in patterns of diseases (through treatment and prevention) will affect the burden of disability (and hence the need for care) and disability-free life expectancy to 2030.

Method

This work builds on a previous simulation model which informed the Wanless Review of Social Care. The model uses the MRC Cognitive Function and Ageing Study, a total population survey encompassing those within institutions and the only UK longitudinal dataset of sufficient size for less common diseases. The first part of the model (the transition phase) quantifies the effect of diseases on transitions to and recovery from disability and to death through trichotomous logistic regression. The ensuing transition rates are then applied to population estimates to simulate the ageing of the population. The current model is being expanded in four ways:

Male and female populations are being projected separately by applying gender-specific transition rates in the simulation model to investigate gender-specific disease scenarios;
Different measures of disability, based on basic and instrumental activities of daily living are being utilised allowing a wider range of severity. In addition a combined measure of physical and mental dysfunction is being created providing greater parsimony with WP5;
New scenarios for future population health are being generated, including the effects of trends in obesity through its relationship with a wider range of diseases and conditions and specifically diabetes, as well as the impact of ethnic minorities into older cohorts with their differential disease-specific mortality and morbidity, using data from systematic reviews of the literature;
Disability-free life expectancy at ages 65, 75 and 85 is being calculated through the combination of the cross-sectional prevalence of disability and the age and gender-specific mortality at each time point using the Sullivan approach.

Linkages

Results of the literature review on diseases and chronic conditions are informing the mortality trends in WP1 (and vice versa). The outputs of disability prevalence are acting as inputs to WP5.

Outputs

As well as serving as inputs to the other models WP2 is producing outputs of interest in themselves, including projections of disability-free life expectancy at ages 65, 75 and 85, prevalence of a range of diseases and conditions and the relative impacts of different future health scenarios on the numbers of older people with varying severity of disability.

Contact

Professor Carol Jagger
Leicester Nuffield Research Unit
Dept of Health Sciences
University of Leicester
22-28 Princess Road West
Leicester LE1 6TP

Tel: 0116 2523211
Fax: 0116 252 5423
Email: cxj@le.ac.uk

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