Some Factors Affecting the Birthday-Deathday Phenomenon

Abstract

Samples of individuals differing in sex, age, profession, eminence and fame, and historical period (total N = 3306) were examined for the presence of the birthday-deathday phenomenon. A decrease in the probability of death with approaching birthday followed by an increase was found in most males. The dip-rise centered on the birthday, spanning on the average thirty-six days before and thirty-six days after the birthday. Females, by contrast, showed an initial rise in the probability of death with approaching birthday, followed by a drop. The phenomenon extended from an approximate average of sixty-five days before to sixty-five days after the birthday. In the general population these two trends may combine to yield a pattern indistinguishable from chance. In addition to gender, age also appears to be a factor in that both the male and the female birthday-deathday phenomena tend to be more pronounced in the elderly. The importance of using time units that are appropriate to the temporal grain of the phenomena is stressed.