Summary
This thesis compared blind women with no light perception (NPL) versus those with light perception (LP), finding that NPL women had a 58% lower adjusted odds of breast cancer and were more likely to exhibit abnormal circadian rhythms. Differences in urinary melatonin and oestrogen metabolites did not explain these outcomes, suggesting light-mediated pathways beyond simple hormonal output may be involved.
Key Findings
- Blind women with no light perception had significantly lower breast cancer risk compared to those with light perception (adjusted OR = 0.42, 95% CI = 0.21–0.85).
- NPL women showed earlier age at menarche (12.2 vs. 12.5 years), correlated with age at loss of light perception.
- Among LP women, only 49% were normally entrained, with 28% non-entrained and 17% abnormally entrained, highlighting high circadian disruption prevalence in partially sighted individuals.
- 40% of NPL women were non-entrained compared to 28% of LP women, confirming that absence of light input strongly disrupts circadian entrainment.
- Urinary melatonin (aMT6s) and oestrogen (e1g) metabolite levels did not significantly differ by light perception status or circadian type, suggesting other mechanisms mediate the breast cancer risk reduction.
Categories
Sleep & Circadian Health: The study investigates circadian rhythm disorders in blind women, classifying entrainment patterns and examining how light perception affects circadian physiology.
The Science of Light: The research directly examines how light perception (or lack thereof) influences hormonal profiles, circadian entrainment, and downstream health outcomes like breast cancer risk.
Author(s)
EE Flynn-Evans
Publication Year
2010
Related Publications
Sleep & Circadian Health
- Phototransduction by retinal ganglion cells that set the circadian clock
- The mammalian circadian timing system: organization and coordination of central and peripheral clocks
- The two‐process model of sleep regulation: a reappraisal
- Melanopsin is required for non-image-forming photic responses in blind mice
- Strange vision: ganglion cells as circadian photoreceptors
The Science of Light
- Phototransduction by retinal ganglion cells that set the circadian clock
- Color appearance models
- The mammalian circadian timing system: organization and coordination of central and peripheral clocks
- Diminished pupillary light reflex at high irradiances in melanopsin-knockout mice
- Melanopsin is required for non-image-forming photic responses in blind mice