Asynchrony between bedtime and circadian time
“Ideally, with this delayed timing of circadian phase, they should have delayed their sleep phase (sleep timing) by an equal amount to be sleeping at their optimal biological time,” Dr. Scheuermaier explained. “Their sleep onset was delayed by 12 minutes (statistically significant but biologically not that much) while their circadian phase was delayed by more than an hour.”
Possible consequences of a smaller phase angle of entrainment include difficulty in initiating and maintaining sleep, the authors wrote. “The shorter, potentially mistimed sleep relative to the endogenous circadian cycle observed in this study provides objectively measured evidence supporting the abundant previous subjective reports of poor sleep quality and insomnia in PLWH.”
They noted that a strength of their study is that participants were recruited from rural South Africa, where HIV prevalence is not confined to the so-called “high-risk” groups of gay men, other men who have sex with men, people who inject drugs, and sex workers.
“Behavioral factors associated with belonging to one or more of these groups would be strong potential confounders for studies of sleep and circadian phase,” they explained. “By contrast, in rural southern Africa, the epidemic has been less demographically discriminating ... There are no notable differences in lifestyle between the HIV– and HIV+ individuals in this study. The members of this aging population are mostly beyond retirement age, living quiet, rural lives supported by government remittances and subsistence farming.”
Direct evidence warrants further study
The study is “unique” in that it provides “the first direct evidence for potential circadian disturbances in PWLH,” agreed Peng Li, PhD, who was not involved in the study.
“The assessment of dim light melatonin onset in PLWH is a strength of the study; together with actigraphy-based sleep onset assessment, it provides a measure for the phase angle of entrainment,” said Dr. Li, who is research director of the medical biodynamics program, division of sleep and circadian disorders, Brigham and Women’s Hospital, Boston.
But actigraphy has limitations that affect the interpretation of the results, he told this news organization.
“Without the help of sleep diaries, low specificity in assessing sleep using actigraphy has been consistently reported,” he said. “The low specificity means a significant overestimation of sleep. This lowers the value of the reported sleep readouts and limits the validity of sleep onset estimation, especially considering that differences in sleep measures between the two groups are relatively small, compromising the clinical meaning.”
Additionally, he explained that it’s not clear whether sleep onset in the study participants was spontaneous or was “forced” to accommodate routines. “This is a limitation in field study as compared with in-lab studies,” he said.
Dr. Li also pointed to the small sample size and younger age of PLWH, suggesting the study might have benefited from a matched design. Finally, he said the study did not examine gender differences.
“In the general population, it is known that females usually have advanced circadian phase compared to males. ... More rigorous design and analyses based on sex/gender especially in this often-marginalized population are warranted to better inform HIV-specific or general clinical guidelines.”
The study was supported by the Academy of Medical Sciences. The authors did not mention any competing interests. Dr. Li reported grant support from the BrightFocus Foundation. The study is not directly related to this paper. He also receives grant support from the NIH through a Departmental Award, Harvard University Center for AIDS Research and a Pilot Project, HIV and Aging Research Consortium. The projects are on circadian disturbances and cognitive performance in PLWH.
A version of this article first appeared on Medscape.com.