During recent decades, China has experienced a rapid transition in the main disease patterns of its population, with a substantial decrease in maternal and child mortality, as well as infectious and parasitic diseases. On the other hand, as a consequence of large changes in lifestyle and increased use of tobacco, mortality from many chronic non-communicable diseases has been increasing steadily. As a result, most of the premature mortality now involves the chronic diseases of middle age, such as stroke, ischaemic heart disease (IHD), diabetes, cancer and chronic obstructive pulmonary disease (COPD). It is estimated that chronic diseases now account for over 80% of deaths and 70% of disability-adjusted life years lost in China (Wang et al. Lancet 2005).
Chronic diseases which are normally associated with affluence (e.g. IHD, diabetes) are more prevalent in urban and coastal regions, whereas chronic diseases associated with poverty (e.g. COPD, oesophageal and stomach cancer) are more common in inland and rural areas. However, for each major disease there is also large unexplained variation in age-specific death rates between different parts of China (Chen et al. JECH 2007). These large unexplained differences in disease rates among areas suggest that avoidable causes of these diseases still await discovery. Moreover, even within one area substantial differences between individual genetic composition, physical characteristics, blood biochemistry, or lifestyle could eventually affect the likelihood of an individual developing a certain disease.
Large prospective cohort studies are an important way of investigating many slow-acting causes of the common chronic diseases in the population. Although there have already been several prospective studies of major chronic diseases in China, each had its limitations, including small numbers of participants, lack of blood samples, involving just one city or occupational cohort, and limited data collection on risk exposures and outcome measures. Consequently, the aetiology of many common chronic diseases in China is still poorly understood, and there is still substantial uncertainty about the present and future relevance to population mortality of many common risk factors, such as smoking. In 2004, we launched a large blood-based prospective study, the China Kadoorie Biobank study, with the goal of recruiting and assessing 0.5 million people and then following their health for a few decades.
What are the main objectives of the CKB?
The CKB is an open-ended study with very broad research aims. The main objectives of the study are: 1) To assess reliably the effects of both established and emerging risk factors for many diseases, not only overall but also under various circumstances (e.g. at different ages and at different levels of other risk factors); 2) To determine the complex interplay between genes and environmental factors and between different genes on the risks of common chronic diseases.