Year: 1998
Type: letter
Abstract: Editors note: The above letter was referred to the authors of the original paper, and their reply follows. In reply: We appreciate this opportunity to respond to the issues raised by Volicer and Harper concerning our paper describing relationships between sleep and circadian rhythms in middle-aged and older individuals. It is conceivable that the large variability in the circadian phase of body temperature (Tmin) in our older sleep-disturbed group may have artifactually diluted the influence of the circadian system on aging sleep. It should be noted, however, that our correlational analysis (J Am Geriatr Soc 1998;46:460), in which all older subjects were considered together, indicated that relationships between circadian rhythm and sleep quality measures were also weak. These already tenuous relationships were weakened further when the influence of age was removed, suggesting that the role of aging per se may influence sleep quality more than aging of the circadian timing system, at least for the type of sleep disturbance considered in this study. We do not agree with Volicer and Harper that some of our sleep-disturbed subjects might have been in the early stages of dementia, thereby increasing the group's variability in circadian phase. These subjects were participants in a protocol in which their cognitive performance was assessed on a relatively complex computerized test battery before and after bright light treatment for their sleep disturbance (J Sleep Research 1996;5:165–172). Although our performance test battery is clearly no substitute for a formal assessment of mental status, these sleep-disturbed subjects were able to perform the test battery without difficulty. It seems unlikely, therefore, that mild dementia in some subjects accounted for the variability in Tmin in our older sleep-disturbed group. Despite the possible limitations of our statistical approach, the data do indicate (and we firmly contend) that there is much more to age-related sleep disturbance than changes in the circadian timing system. In this regard, we have shown that ‘correcting’ the circadian rhythm changes in individuals with sleep maintenance insomnia does not totally alleviate the sleep disturbance (J Am Geriatr Soc 1993;41:829–836). Likewise, advancing the circadian phase of younger subjects does not induce the severity of sleep disruption observed in older sleep maintenance insomniacs (J Sleep Res 1992;1:205–210). We believe that studies investigating the bases of sleep disturbance in aging should consider, with equal weight, the possible roles of alterations in the circadian timing system and the wide range of alternative possibilities including age-related changes in homeostatic pressure for sleep, age-related changes in hormonal systems mediating sleep, and overall medical status, that are as yet unexplored.
Authors: Scott S. Campbell, Patricia J. Murphy
Language: English
Subfield: Endocrine and Autonomic Systems
Field: Neuroscience
Domain: Life Sciences
Open Access status: bronze
OpenAlex ID: W4247745656