ABSTRACT
Studies examining the effects of aging on the circadian system can be conve niently categorized by the experimental paradigm employed in those studies. By far, the vast majority of such research, particularly in humans, has examined rhythms under entrained conditions. Far fewer studies have probed for age effects under free-running conditions, during constant routine protocols, during forced desynchrony interventions, or subsequent to experimental phase shifts. In this chapter we will review relevant studies in each of the areas; however, the reader should bear in mind the total data base on which age effects on the circadian system are inferred using protocols other than under entrainment is sparse and originates from only a handful of research groups.
