Circadian rhythm abnormalities in totally blind people: Incidence and clinical significance

Robert L. Sack, Alfred J. Lewy, Mary L. Blood, L. Donald Keith

Research output: Contribution to journalArticlepeer-review

320 Scopus citations

Abstract

When people are completely isolated from environmental time cues, their circadian rhythms free run with a nearly 24-h cycle, generated by an internal body clock. Free-running temperature, cortisol, and melatonin rhythms have also been described in totally blind people, even though they were living in normal society and had access to abundant time cues; thus an intact visual system may be essential for synchronization of the circadian system. However, because of the small numbers of subjects studied, the incidence and clinical significance of circadian rhythm abnormalities among the blind has remained uncertain. In this study, plasma melatonin (n = 20), cortisol (n = 4), and sleep propensity (n = 1) were measured in serial samples taken from totally blind subjects for 24 h. Most totally blind subjects had circadian rhythm abnormalities. In about half of the subjects, the rhythms were free-running. Some blind subjects suffered recurrent insomnia and daytime sleepiness that were maximal when the internal rhythms were out of phase with the preferred sleep times. The high incidence of abnormal circadian rhythms in blind people underscores the importance of the light-dark cycle as an important environmental synchronizer for the human circadian system.

Original languageEnglish (US)
Pages (from-to)127-134
Number of pages8
JournalJournal of Clinical Endocrinology and Metabolism
Volume75
Issue number1
DOIs
StatePublished - Jul 1992

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Biochemistry
  • Endocrinology
  • Clinical Biochemistry
  • Biochemistry, medical

Fingerprint Dive into the research topics of 'Circadian rhythm abnormalities in totally blind people: Incidence and clinical significance'. Together they form a unique fingerprint.

Cite this