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Article
April 2, 1997

Sleep Quality in Older Adults: Effects of Exercise Training and Influence of Sunlight Exposure-Reply

Author Affiliations

Stanford University School of Medicine Palo Alto, Calif
Emory University School of Medicine Atlanta, Ga

JAMA. 1997;277(13):1034-1035. doi:10.1001/jama.1997.03540370024018
Abstract

In Reply.  —Drs O'Connor and Youngstedt raise some interesting issues with respect to the potential role that exposure to sunlight accompanying increases in outdoor physical activity could have on improvements in sleep quality. We agree that the mechanisms through which increases in physical activity affect rated sleep quality remain to be elucidated.Although it is conceivable that light exposure could have been a factor in producing the study results, there are several aspects of our study that raise doubts that change in light exposure was an important mediator of the sleep-quality changes observed. First, there was no evidence of any shifts in the time of night at which study subjects went to bed following the 16-week exercise training program. This suggests no circadian phase shift, as was posited by the authors. Even if there were a shift in reported bedtime, this would not prove that light was the crucial factor. For instance,

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