In 24 hour cycles and in yearly cycles your entire body, and also each individual body system and also each individual cell performs and ceases to perform the same productivity and then repair functions over and over repeatedly, as per the timing alerts originating from the trillions of circadian rhythm clocks contained within one person.
All of these trillions of clocks work as one clock via synchronization. The neurotransmitter/hormone melatonin plays a role in this synchronization process.
Each cell individually has its own circadian clock, and this multitude of clocks are synchronized to the master clock in the brain (SCN), and the master clock in the brain is synchronized to the 24 hour daily cycle (for day and night adaption) and also to the yearly motion of the earth about its yearly circuit around the sun (for winter and summer adaption).
The way the master clock (SCN) in the brain is synchronized to the environment is by the intensity and the duration and the spectral composition of light entering the eyes (or not entering the eyes).
Conversely, circadian disruption can mean that the circadian cycle swing between productivity and repair cycles is weakened and blurred, improperly advanced or delayed, stopped in place or that various clocks are no longer synchronized to each other or the environment.
Circadian disruption is a natural result of modern artificial lighting, because no where on planet earth are there 16 hour days for 365 days a year. Your body was made to function with the light timing and spectral content that nature provided.
Modern lighting informs your master clock in your brain (SCN) through your eyes that daylight is occurring 16 hours everyday for all 365 days per year.
Such retinal light exposure holds the circadian yearly rhythm in the permanent summer adaptation, where a person's body is always carb craving to prepare for the following winter that never comes.
Such retinal light exposure also usually results in delaying the repair portion of the 24 hour circadian rhythm and thus shortens the repair portion of the cycle.
Circadian disruption for the 24 hour cycle causes endothelial dysfunction and chronic endothelial dysfunction results in vascular remodeling injury, which contributes to heart disease.
Imagine this, if a person could make their cholesterol and triglycerides and blood sugar and blood pressure totally perfect, but if this person were to allow circadian disruption from allowing their endothelial cells from properly migrating to routinely re-smooth the vascular walls, this person would still be in danger of a heart attack. This is because non extraordinary forces cause the vascular walls to eventually change, which change will allow for turbulent blood flow. This turbulent blood flow encourages clotting.
So, although I still use my computer at night as I did when I suffered a heart attack years ago, but now I do so while wearing orange lens eyewear because I believe this protects my artery walls from becoming un-smooth. I believe that my protection of my circadian health/endothelial health is why I stopped needing more stents (at least up to this day).
This research paper is completely free.
I suggest anyone working a night shift consider wearing red lens eyewear prior to attempting sleep during the day and that day shift persons using any kind of artificial lighting at night, wear orange or yellow lens eyewear, hours prior to attempting sleep TO MAINTAIN ROBUST ENDOTHELIAL FUNCTION.