Time and time again: The effects of biological rhythms on human health and performance

With rhythms existing at all levels of biological organization, from subcellular structures to ecological systems, and exhibiting a variety of frequencies, from the millisecond cycles of sensory neurons to the 11 year cycles in lynx and hare populations found in northeastern North America, a number of different mechanisms can be inferred. However, whole organism rhythms of behavior and physiology are often mediated by self-sustaining oscillators of clocks and this paper focuses on these kinds of cycles. The topics discussed include: exogenous and endogenous rhythms; circa-rhythms; circadian clocks; and the role of rhythms in health and performance (seasonal affective disorder, jet travel; shiftwork; temporal patterns in risk and susceptibility) and circadian management of cancer