Prospective study of 500,000 adults in Chennai (Madras), India
The Chennai Prospective Study (1) is led by Chennai-based epidemiologist, Dr Vendhan Gajalakshmi, with whom the CTSU collaborates extensively. The study surveyed 500 000 men and women aged 35 years or more in 1998-2001, collecting information on smoking, chewing habit, alcohol consumption, weight, height, waist circumference (in men only), blood pressure and medical history. Participants have, since then, been followed up for cause-specific mortality not only by record linkage to routine mortality and cancer registry data, but by fieldworker home visits in which the cause of death is sought by verbal autopsy (2). In the verbal autopsy, an informed person (usually a family member) is asked by a trained graduate non-medical fieldworker to describe the illness, its treatment and any other relevant information, and a narrative of these is written down, usually in the local language. This recorded narrative information is subsequently reviewed blindly by two medical doctors to arrive at a probable underlying cause of death (with subsequent adjudication of any important discrepancies in their ICD-10 code assignments). This method of verbal autopsy (ie, non-medical fieldwork plus two doctors coding the written narrative independently) was developed largely by Dr Gajalakshmi, and it is currently being adapted by India’s Registrar General for use more widely throughout India. The Chennai Prospective Study builds on the work of an earlier retrospective (case-control) study in Chennai which, among other findings, indicated that the chief disease by which tobacco smoking is killing men in South India is tuberculosis (3). The prospective study will provide even more robust evidence about this and other risk factor-disease relationships in South India.
(1) Gajalakshmi V, Peto R, Kanimozhi VC, Whitlock G, Veeramani D. Cohort profile: The Chennai prospective study of mortality among 500 000 adults in Tamil Nadu, South India. International Journal of Epidemiology 2007 (in press)
(2) Gajalakshmi V, Peto R. Verbal autopsy of 80,000 adult deaths in Tamilnadu, South India. BMC Public Health 2004; 4: 47
(3) Smoking and mortality from tuberculosis and other diseases in India: retrospective study of 43 000 adult male deaths and 35 000 controls. Lancet 2003; 362: 507-15
