Modal Age at Death: Lifespan Indicator in the Era of Longevity Extension

Shiro Horiuchi, CUNY Institute for Demographic Research (CIDR)
Nadine Ouellette, University of California, Berkeley
Siu Lan Karen Cheung, University of Hong Kong
Jean-Marie Robine, Institut National de la Santé et de la Recherche Médicale (INSERM)

We examine and demonstrate importance of the adult modal age at death (M) in longevity research. Unlike the life expectancy at birth (e0) and median age at death, M is determined solely by old-age mortality as far as mortality follows the regular pattern. It represents the location of “old-age death heap” in the age distribution of deaths, and captures mortality shifts more accurately than conditional life expectancies such as e65. Due to these characteristics, patterns of trends and differentials in M can be noticeably different from those in other lifespan measures, as indicated in some examples. In addition, M plays central roles in major models of adult mortality such as the Gompertz, logistic and Weibull models. Although M may not be directly determined from erratic mortality data, a recently developed method for deriving M from the P-spline-smoothed mortality curve based on penalized Poisson likelihood is highly effective in estimating M.