A new method for correcting the underestimation of disabled life expectancy inherent in conventional methods: application to the oldest old in China

This article demonstrates that the widely used disabled life expectancies based on conventional methods are significantly underestimated due to assuming no functional status changes between age and death. We propose a new method to correct the bias and apply it to the longitudinal survey data of about 9,000 oldest old Chinese aged 80-105 collected in 1998 and 2000. In our application the age trajectories of ADL status-specific death rates and ADL state transition probabilities of the oldest old were investigated for the first time in a developing country. We have estimated the bias-corrected disabled and active life expectancies of Chinese oldest old, and demonstrate patterns of large differentials associated with initial status, gender and advances in ages. Employing combined information on ADL and length of having been bedridden before dying, we analyze gender and age patterns of the extent of morbidity before dying among the oldest old and the implications of the debating hypothesis of compression of morbidity.