Christopher Bingham

Most of us are to some extent slaves to the clock. We wake up, eat meals, go to work or school, and go to bed at roughly the same time each day. It is thus no surprise that many physiological indices--blood pressure, heart rate, hormonal levels, alertness, to name only a few--vary rhythmically with a period of 24 hours. What some find surprising is that this rhythmicity persists even in a constant environment with no time cues--for example, deep in a mine without a clock--although the period may shift to, say, 25 hours or 23 hours. In fact there is evidence for endogenous circadian (about a day) rhythms in many organisms, from the unicellular to humans. Even in an environment with a 24-hour period, individual periods can become desynchronized and deviate from 24 hours. Understanding biological rhythms is an important part of the field of chronobiology, the study of biological time patterns. The statistical analysis of time patterns is chronobiometry, and is one of my current active interests. In this work, I use regression, time series analysis, and multivariate analysis. The findings of chronobiology have important implications for medicine, agriculture, and ecology. An incorrect diagnosis of hypertension may result from ignoring the time of day when blood pressure is measured. The disturbance of physiological rhythms may be an important diagnostic clue of disease. Because the susceptibility of tumors to chemotherapy can vary rhythmically, the timing of a treatment can affect the efficacy of the therapy. The time of day a plant is inoculated with a pathogen can affect the development of a disease. Among the many statistical problems of chronobiometry are period estimation, wave form description, discrimination on the basis of chronobiological end points, and the design of experiments that efficiently include time as a factor.