Cohort Profile: The Kadoorie Study of Chronic Disease in China (KSCDC)

During recent decades China has undergone a rapid transition in the main disease patterns of its population. There has been a substantial decrease in maternal and child mortality and in adult mortality from themain infectious/parasitic diseases, whereas for ischaemic heart disease and some other non-communicable chronic diseases, there has been a moderate increase in mortality rates, at least in some parts of China. Consequently, most of the premature mortality that still remains in China now involves the chronic diseases of middle age, such as cancer, stroke, heart disease, or chronic lung disease. 1–4 In the mid-1970s a retrospective survey of the causes of 20 million deaths in China during 1973–75 showed that for each major disease there was large unexplained variation in the age-specific rates between different parts of China, indicating that there must be some large avoidable causes. 5 This finding was confirmed and extended in the late 1980s by a more careful retrospective survey of the causes of one million deaths during 1986–88 in 69 rural counties and 24 cities (Figure 1). 3,4 These big differences in disease rates between one area and another probably reflect differences in the ways people live rather than genetic differences. Moreover, even within one area there are likely to be substantial differences between individuals in genetic factors, as well as in patterns of chronic infection, personal biochemistry, physical characteristics, lifestyle, etc. that persist for many years and eventually influence the likelihood of particular individuals developing particular diseases. 3,4