1.2 Literature Review

Considering the fact that older people currently constitute the majority of those in poor health, the determinants of health in old age are a growing concern.

The International Classification of Functioning, Disability and Health, often referred to as ICF, is a classification of health and health-related domains by all 191 WHO Member States in the fifty-four World Health Assembly in 2001. ICF acknowledges that every human being would experience a decline in health, but the extent to which the health of an individual is impaired could be totally different. A list of environmental factors was also included in the ICF, as well as personal factors, since an individual's health occurs within a context. Thus, changes in the social and ecological environments could alter health conditions（Figure 1-7）.

Figure 1-5 Population aging trend in China from 1950 to 2010

Source: United Nations, Department of Economic and Social Affairs, Population Division.（2013）. “World population prospects: the 2012 version”. Retrieved from http://esa.un.org/unpd/wpp/Excel-Data/population.htm.

Figure 1-6 Age structure of Chinese population in 2000

Source: National Bureau of Statistics of the People's Republic of China.（2000）. The fifth national population census. “National population by age and sex”（in Chinese）. Retrieved from http://www.stats.gov.cn/tjsj/ndsj/renk-oupucha/2000pucha/html/t0301.htm.

Figure 1-7 ICF model

Source: World Health Organization.（2001）. “International Classification of Functioning, Disability and Health”. Retrieved from http://www.who.int/classifications/icf/en/.

Both in western industrialized countries and developing countries, every improvement in human health of the history is not only ascribed to advances in medical technology, but also to the development in the economy and environment. However, in modern society, the contribution of advancement in medical knowledge and technology to population health is diminishing（accounts for only 10%）. Population health was mainly determined by personal health behaviors（50%）, social environment（20%）and heredity（20%）. Therefore, social determinants which were basic and sustainable for national health gradually attracted more attention and were taken into consideration.

Similarly, from the perspective of multiple etiology, in addition to genetic and physical factors, health problems and diseases were also caused by a wide variety of social determinants that were at the root of these inequalities in health. On the basis of causal distance to health, social determinants could be divided into three levels: proximal factors, mid-range factors and distal factors. Proximal factors which could be easily changed by individuals are closest to health, including health-related lifestyles and behaviors; social relationships and social support are regarded as mid-range factors; and distal factors cover social structure and stratification, over which people have the least control.