With rapid changes of demographic structure and lifestyle, disability should be an important indicator of health evaluation and health promotion. However, due to the limitation of ideas and methods, research on the trend of disability is limited. Using data from the first and second China National Sample Survey on Disability (CNSSD) in 1987 and 2006, we restored the prevalence of population disability and its change trajectory in China during 110 years from 1896 to 2006 across 3 centuries through an innovative application of interdisciplinary methods. We found that since the end of the 19th century, the prevalence of disability among Chinese population presented a trend of fluctuating decreases, decreasing rapidly, and then increasing slowly. Three stages of evolution, which are closely related to the characteristics of social development and changes in mortality, were presented as dividing points in 1949 and 1986. The findings highlight that to further prevent and control disability and improve healthy life expectancy should be the main task and goal of health promotion.
Data used in this study were obtained from the first and second CNSSD in 1987 and 2006. Details about sampling, quality and key conceptions of the surveys can be found in our previous work (1-2). The two cross-sectional surveys contained the time of disability occurrence which was used as a key parameter to estimate the prevalence of disability in the previous 110 years. Data on total population, natural growth rate of population, mortality, etc., involved in calculations were derived from public information such as statistical yearbooks and literature.
Disability may occur under the combined effect of various risks of disability in the course of an individual’s life from birth to death. At the population group level, the disability status of a population is a dynamic process consisting of new disabilities, disability rehabilitation, and death of the persons with disability. Thus, we established a flow chart of the disability process for a population as Figure 1 and considered simultaneous formulas with corresponding parameters to estimate the prevalence of disability in the previous 110 years since 2006 by mirroring reverse receding. The estimation process and details of calculation method were illustrated in Supplementary Figure S1.
Figure 2 shows the results of the restoration of population disability trajectory during 110 years from 1896–2006 across 3 centuries in China. In 1896, the starting point of this restoration, the prevalence of disability was nearly 55%, and then gradually declined with relatively frequent fluctuations in a certain period. On the whole, since the end of the 19th century, the prevalence of population disability in China presented a trend of decreasing in fluctuation, decreasing rapidly and then increasing slowly.Figure 2. Restoration of population disability trajectory in China, 1896–2006. Note: Major events for examples, a serise of wars during 1919–1948, the great famine during 1959–1961, earthquakes in 1996 and floods in 1998.
Further observing the disability trajectory combined with changes of population mortality, we divided the development of population disability in China from 1896 to 2006 into 3 stages, with the dividing points of 1949 and 1986.
Stage I was from 1896 to 1948, i.e., social upheavals and war years, during which the prevalence of disability of China declined from a high level in fluctuations, and the trend was opposite to that of mortality. Since it is difficult to obtain more accurate information on mortality in the early stages of history, we began to compare disability with mortality in Stage I since 1919, when relatively accurate figures of death were available. It is obvious from Figure 2 that during 1919–1948, both disability and mortality showed frequent fluctuations, and the “peaks and valleys” of the two generally fluctuated in the opposite direction.
Stage II was from 1949 to 1985, i.e., the period of founding and early construction of new China, during which the prevalence of disability declined rapidly and showed the same trend as the mortality. And the decline of the prevalence of disability was faster than that of mortality.
Stage III was from 1986 to 2006, i.e., development and deepening of medical reform period, during which the prevalence of disability tended to rise and moved in the opposite direction of mortality. Both the rise of disability and decline of mortality were slow.