Academic journal article Demographic Research

A Multistate Model to Project Elderly Disability in Case of Limited Data

Academic journal article Demographic Research

A Multistate Model to Project Elderly Disability in Case of Limited Data

Article excerpt

(ProQuest: ... denotes formulae omitted.)

1. Introduction

In the coming decades, many western European countries will face a strong increase in the number of the elderly, as the large post-war baby boom generations are currently starting to reach the age of 65. Simultaneously, the number of the oldest old is growing rapidly as a result of increasing longevity (Oeppen and Vaupel 2002). Although different population scenarios for Europe may project different future populations, all scenarios show significant increases in the numbers of the elderly (Eurostat 2008, 2011, 2014; Scherbov, Mamolo, and Lutz 2008; De Beer et al. 2010; Huisman et al. 2013; Rees et al. 2013; United Nations 2014; KC and Lutz 2014). Since health care and long-term care consumption by the elderly, especially by the very old and frail, is well above average, demand of long-term care and health care expenditures are likely to increase significantly (Meerding, Bonneux et al. 1998; Meerding, Polder et al. 1998; Gray 2005; Comas-Herrera et al. 2006; Pavolini and Ranci 2008; Przywara 2010; Rodrigues, Huber, and Lamura 2012). The extent to which this demand will increase depends on the future health status of the elderly population. If the average health status will improve, long-term care need may increase to a lesser extent than the number of elderly persons. On the other hand, if disability increases strongly at very old ages, increasing life expectancies may lead to additional increases in the demand for care. The health status of the elderly is closely related to medical innovations. Improvements in health care may result in better survival, but may extend life in disability. For example, the sharp decline in acute coronary heart disease mortality has increased the number of survivors with heart failure (Bonneux et al. 1994; Peeters et al. 2003; Bonneux 2011).

To address policy questions related to the provision of health care services in an ageing population, it is important to know how many people will face disability in very old age. Today, the after-war baby boom cohorts starting in 1946 are reaching old age, making forecasts of the number of disabled elderly even more important for policy makers.

The two main methods used to calculate the future number of disabled elderly are the Sullivan method (Sullivan 1971) and the multistate model (Rogers, Rogers, and Branch 1989). The Sullivan health expectancy reflects the current health of a real population, adjusted for mortality levels and independent of age structure (Jagger, Cox, and Le Roy 2007). This indicator is based on prevalence data and can be used to compare the health status of a population at two points in time, or of two different populations at the same time. Using disability prevalence data, the future number of disabled elderly can be estimated by projecting the future number of elderly persons, and by subsequently multiplying this number by the percentage of the elderly that is expected to be disabled. Disability numbers can be estimated by analyzing past trends in the prevalence of disability and by assuming that these trends will continue in the future. This procedure, however, does not take into account the interaction between changes in mortality and changes in disability. In practice, disability and mortality are related in several ways. First, trends in medical progress that affect mortality may also be expected to affect disability. Second, risk factors that affect both mortality and disability, such as the prevalence of obesity or smoking, may be expected to change over time and may affect mortality and disability in a different way. Finally, mortality rates may differ between non-disabled and disabled persons. In order to take these interdependencies into account in making projections, it is necessary to use a multistate projection model.

Multistate projection models use disability incidence rates to estimate the number of transitions into disability and the number of deaths. …

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