Health research on a massive scale: the China Kadoorie Biobank

China is a vast country, with almost one-fifth of the world's population, mostly drawn from the same ethnic group, the Han. In the past its people have suffered from many of the illnesses associated with poverty. Today these health risks are rapidly being overtaken by the chronic diseases often associated with a more affluent lifestyle.

Oxford's Clinical Trial Service Unit and Epidemiological Studies Unit (CTSU) has a history of research in China that goes back almost 30 years. In the early 1980s Professor Sir Richard Peto, working with colleagues from Chinese institutions, began the first of a series of epidemiological studies documenting the wide variation across China in diet, environment and other factors, and a parallel variation in causes of death. Since then further studies have provided the first links, in a Chinese context, between lifestyle factors and illness, notably between tobacco smoking and premature death.

With the China Kadoorie Biobank (CKB), directed jointly by Professor Zhengming Chen of CTSU and Professor Liming Li of the Chinese Academy of Medical Sciences, observational epidemiological research has moved into a new era. With funding from the Kadoorie Foundation in Hong Kong, 510,000 volunteers from ten geographically diverse regions of China have contributed detailed information on their lifestyle, undergone a battery of physical measurements, and donated blood samples.

The value of this study depends not only on its unique size and the richness of the initial information it contains, but also on being able to follow the health of the participants for decades. Professor Chen is delighted that this task has just been made much easier: China has introduced a national health insurance scheme covering almost the entire population. Now that each participant has a unique identification number, CKB has been able to link to this national system, making it possible to retrieve detailed records of hospital admissions.

'Originally we thought we would only be able to retrieve death certificates through established registries,' says Professor Chen, 'but so far we've recorded more than 200,000 episodes of hospitalisation.' The link means that researchers can now study both fatal and non-fatal conditions, as well as follow the 'natural history' of a patient: what happens after a heart attack, for example? Already Professor Chen and his colleagues have identified over 10,000 new cases of stroke from within the CKB cohort. With advances in DNA sequencing technology, he and Professor Peter Donnelly of Oxford's Wellcome Trust Centre for Human Genetics hope to compare the genetic make-up, lifestyle factors and blood biochemistry of these patients with 10,000 similar CKB participants who have not had strokes.

'China has large, regional variations in patterns of disease that cannot be explained by known risk factors,' says Professor Chen. 'Important, avoidable causes still await discovery. With Oxford's long tradition of managing large, population-based research, and China's excellent infrastructure, there is huge potential.'