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Changes in total and disability-free life expectancy among older adults in China: Do they portend a compression of morbidity?

1.2 Trends in Disability Prevalence and Disability-free Life Expectancy

A common way of assessing which scenario is occurring has been to examine disability
trends. There is a long history of such research in the United States where population ag-
ing has been a concern for some time and reliable data exists to monitor changes over the
relatively long term. Much of this research has been summarized by Freedman and col-
leagues (2002 and 2004). The general conclusion is that the 1960’s and 1970’s saw in-
creases in disability rates (Colvez and Blanchet, 1981). More recently there have been per-
sistent declines (Martin et al., 2010; Schoeni et al., 2001). Some of the turn-around is a
function of population composition. In particular, education tends to be inversely associa-
tion with disability and there is a rising proportion of more educated in the older popula-
tion (Freedman and Martin, 1999).
A more direct way of determining whether longer and healthier lives are being lived is
to observe changes to healthy or active life expectancy. These are measures that evaluate
number of years or proportion of remaining life an individual can expect to live in a
healthy state. Disability-free life expectancy (DFLE) is derived from these general meas-
ures and focuses on separating total life expectancy (TLE) into years expected to be lived
with and without disability (Saito et al., 2014). The most pessimistic scenario relates to
TLE rising but DFLE remaining stagnant, indicating extra years of life are being lived in
states of disability (Crimmins et al., 1989) The most optimistic scenario, and one that
would comport with a compression of morbidity, would see DFLE rising faster than TLE
(Fries, 1980). While there have been a series of DFLE estimates in the United States and
in other developed countries, only a few studies have examined trends over time, notably
those by Crimmins and colleagues (1997, 2001, 2009). In general, these studies indicate
changes in DFLE in the U.S. are, with some variation, paralleling increases in TLE.
Despite rapid demographic changes taking place in China, similar research there has
been scarce, partially due to data availability. However, in recent years there have been
several attempts to examine disability trends for the total country or sub-regions (Feng et
al., 2013; Zimmer et al., 2014; Gu et al., 2009). Liu et al. (2009) examined changes in
TLE and DFLE and concluded a compression of morbidity was occurring, particularly
amongst oldest-old. There have been a scattering of studies on disability prevalence and
DFLE trends across other countries in the region (Schoeni et al., 2006; Ofstedal et al.,
2007; Martin et al., 2011; Chou et al., 2008). These findings have been inconclusive.
Trends in disability generally may be seen as improving, however this is not the case eve-
rywhere and trends do not necessarily hold when socio-demographic and economic control
variables are added.

1.3 Using DFLE to Assess Longer Life Versus Healthier Life

DFLE has been widely used for comparing health across populations and examining how
health has been changing over time (Saito et al., 2003; Jagger et al., 2009; Robine et al.,
2001). Comparing TLE and DFLE over time allows for an assessment of whether longer
life and better health is occurring simultaneously, the scenario consistent with a compres-
sion of morbidity. These comparisons can be made in different ways. One comparison is
whether net increases in DFLE match increases in TLE. This is an indication of whether,
on a population-wide level, extra years of life are being lived without disability. More ap-
plicable for the current study is the ratio of DFLE to TLE, or the proportion of remaining
life without disability. An increasing ratio speaks of relative gains — again on a popula-
tion-wide level. It is possible that the net DFLE increase does not match the net TLE in-
crease, but because DFLE is always something less than TLE, the relative increase may
match or be greater. While this might mean that not all additional years of life are spent

International Journal of Population Studies | 2015, Volume 1, Issue 1 6