The role of aging in cancer incidence: an epidemiological study

Age-specific and age-standardized incidence rates for cancers of the bronchus, stomach, colon, rectum, pancreas, skin, male bladder, and female breast, uterus, and ovary in 1975 were studied in populations throughout the world, and, for bronchus and stomach cancers, over time from 1960 to 1975. The variation in age-specific rates with age was similar for all cancers, as demonstrated by large positive correlation coefficients between age-incidence patterns averaged over all populations. In addition, the age-incidence patterns for bronchus and stomach cancer were similar and essentially invariant over time. The variation in age-standardized rates among the populations was not similar for all cancers, as demonstrated by correlation coefficients that were small in some cases and negative in others. Between bronchus and stomach cancer, age-standardized rates varied in opposite directions from 1960 to 1975. It is obvious, therefore, that the cause for the variation in age-specific rates with age is not related to the cause for the variation in age-standardized rates among populations or over time. The shape of age-incidence patterns for the cancers studied must be determined by a factor that is common to the tissues of tumor origin, and invariant among populations and over time. The intrinsic aging process is the most reasonable candidate for this role.