Rising primary malignant brain tumor mortality in the elderly. A manifestation of differential survival

J. E. Riggs
Department of Neurology, West Virginia University School of Medicine, Morgantown, USA.

BACKGROUND: Increasing primary malignant brain tumor mortality among the elderly in developed countries over the past three decades has been attributed to improved diagnostic techniques and increased environmental carcinogens. OBJECTIVE: To demonstrate that rising primary malignant brain tumor mortality among the elderly can be accounted for by differential survival. DATA SOURCE: Published United States mortality data from the National Center for Health Statistics, 1962 to 1989. MEASURES: Age-specific primary malignant brain tumor mortality rates were determined for the age groups of more than 60 years old and compared with the population size of these age groups. RESULTS: Increasing primary malignant brain tumor mortality rates among the oldest age groups in the United States from 1962 to 1989 were directly proportional to the increasing population size of these age groups. CONCLUSIONS: Comparisons between age-specific mortality rates are generally considered valid since they are inherently age- and sex-matched. Moreover, age-specific mortality rates should not be related to population size. Rather than implying improved diagnosis or enhanced carcinogenesis, these results suggest that differential survival and its effect on the surviving gene pool in an aging population is an alternative explanation for the observed increase in primary malignant brain tumor mortality among the elderly.