John is blind and is therefore unable to detect light that normally sets the Suprachiasmatic Nucleus (SCN). If he is like most blind people: His sleep-wake, body temperature, and melatonin circadian rhythms can become desynchronized.
What does blindness do?
Blindness often disrupts the normal light-entrainment of the Suprachiasmatic Nucleus (SCN), which plays a crucial role in regulating circadian rhythms. As a result, John is likely to experience desynchronization of his sleep-wake cycle, body temperature, and melatonin secretion.
Insomnia or excessive daytime sleepiness: The lack of light cues can make it difficult for John to fall asleep and wake up at consistent times.
Disrupted body temperature regulation: John's body temperature may not follow the normal circadian rhythm, leading to fluctuations that can interfere with sleep and other bodily functions.
Reduced melatonin production: Melatonin is a hormone that helps regulate sleep and wakefulness. Without the normal light cues, John's melatonin production may be reduced, further contributing to sleep problems.