The biphasic pattern of age-specific malignant brain tumor mortality rates

Many aging-associated neurologic disorders, including primary malignant bra in tumors (MBT), share a common biphasic age-specific mortality rate patter n: initially increasing exponentially with age, and then declining. A model ing study using MBT mortality was conducted to determine if the observed bi phasic pattern of MBT age-specific mortality rates emerges if one assumes t hat there exists a population subset that is inherently susceptible to MBT, and that the risk. of mortality from MBT in that susceptible population su bset continues to increase exponentially with age. A hypothetical populatio n was subjected to 1988 general mortality risks. A population subset suscep tible to MBT was subjected to both exponentially increasing 1988 general an d MBT mortality risks. Expected MBT age-specific mortality rates in the tot al population (both general and MBT susceptible subsets) were determined. E xpected MBT age-specific mortality rates in the total population initially increase exponentially with age, and then decline. Moreover, when the size of the MBT-susceptible population subset was set at 1/125 of the size of th e general population size, the modeled pattern of age-specific MBT mortalit y rates closely mimicked the observed pattern of age-specific MBT mortality rates. The observed biphasic pattern of age-specific MBT mortality rates c an be explained by the existence of an MBT-susceptible population subset in whom the risk of MBT mortality increases exponentially with age and popula tion subset depletion occurs.