Circadian Rhythm Disorders and Melatonin Production in 127 Blind Women with and without Light Perception.
Level 4 - case-series / case-control
Observational cross-sectional field study
PubMed 24916394 · doi:10.1177/0748730414536852
What was done
An 8-week field study assessed circadian rhythm entrainment in 127 blind women (mean age 50.8 ± 13.4 years) categorized by presence (LP, n = 86) or absence (NPL, n = 41) of light perception. Participants maintained daily sleep diaries and collected sequential 4- to 8-hourly urine samples over 48-hour periods on 2 to 3 occasions separated by at least 2 weeks. Circadian status was determined from cosinor-derived urinary 6-sulfatoxymelatonin rhythm peaks across different ocular diagnoses.
What was found
In participants with no light perception (n = 41), 39% were nonentrained, 24% were abnormally phased, and 37% were normally entrained. In participants with light perception (n = 86), 69% were normally entrained, 21% (n = 18) were abnormally phased (8 advanced, 10 delayed), and 10% (n = 9) were nonentrained. Abnormal phase or nonentrainment occurred in 67% of participants with bilateral enucleation and 57% with retinopathy of prematurity, whereas normal entrainment was preserved in 84% with retinitis pigmentosa and 83% with age-related macular degeneration.
Why it matters
This study shows that circadian entrainment in visual impairment depends not only on subjective light perception but also on the specific underlying etiology and whether it preserves non-visual photoreception.
Limits
The cohort included only female participants, limiting generalizability to males. The field-based design relied on self-reported sleep diaries and self-collected urine specimens rather than in-laboratory constant routine protocols. Subgroup sample sizes and inferential statistics for specific ocular etiologies were not provided in the abstract.
Cited by
- supports Visually blind humans and animals can still photoentrain their circadian rhythms to light-dark cycles, whereas individuals who have had both eyes surgically removed lose light entrainment and free-run.