The Sans of Time

To the Editor. —We were interested in the ideas presented by Drs Lipshitz and Goldberger regarding chaos theory and aging.1We would like to take minor exception to their definition of "aging" and point out some recent information concerning the other end of the "arrow of time." The authors define aging as a progressive loss of complexity. Clearly they have in mind the onset of senescence when they state this definition. Aging is a process that extends back to fetal life and at first shows an increase in complexity. Gough recently published his analysis of the fractal nature of beat-to-beat heart rate interval in a 37-week-gestation infant during intrauterine monitoring.2Using the "coastline" method, he demonstrated that the complex feedback loops necessary for deterministic chaos must already be intact by this gestational age. One of us (D.B.S.) has been studying beat-to-beat interval with spectral analysis serially in 24