Season-of-birth and acute leukemia of infancy.

Because of its short and clearly delineated latency period, acute leukemia of infancy is particularly suited to etiologic analysis. From 1950 to mid-1985, 31 infants with acute leukemia (less than 1 year of age) were registered at the University of Texas, M.D. Anderson Cancer Center at Houston. The medical records of these infants were reviewed for demographic and birth information. Of the 31 infants, 14 (45%) were Hispanic. The sex ratio was 3:1 male/female) for white infants and 5:9 for Hispanic infants. Of the white infants, half had acute lymphocytic leukemia, compared with all but one of the Hispanic infants. There was a significant excess of winter births among the infants diagnosed with acute leukemia (P less than 0.05). The significant association between season-of-birth and the occurrence of leukemia cases is suggestive of periodicity of an environmental etiologic agent, perhaps acting in concert with endogenous rhythmicities in susceptibility to that agent. This finding is deserving of further study.