The recruitment of the cohort during 1969-73 was based on the population census carried out in Vellore town and adjoining villages (KV Kuppam rural development block, one among 20 blocks) in the North Arcot (now Vellore) district in Tamil Nadu state, India. The urban area consisted of about one-third of Vellore town representing different socio-economic strata and the rural area comprised 26 of 42 contiguous villages representing different socio-economic strata (Figure 1).