Circadian disruption by night light linked to multiple cardiovascular outcomes

Medical Xpress / medRxiv ^ | July 6, 2025 | Justin Jackson / Daniel P Windred et al

[ConservativeMind]

Researchers have linked brighter night-time light exposure to elevated risks of five major cardiovascular diseases.

Circadian rhythms govern fluctuations in blood pressure, heart rate, platelet activation, hormone secretion, and glucose metabolism. Long-term disruption of those rhythms in animal and human studies have produced myocardial fibrosis, hypertension, inflammation, and impaired autonomic balance.

Researchers conducted a prospective cohort analysis to assess whether day and night light exposure predicts incidence of cardiovascular diseases and whether relationships vary with genetic susceptibility, sex, and age.

Data came from 88,905 UK Biobank participants, average age 62.4 ± 7.8 years and 56.9% female, who wore wrist-based light sensors for one week between 2013 and 2016.

Hazard modeling linked night and day light exposure percentiles with new diagnoses of coronary artery disease, myocardial infarction, heart failure, atrial fibrillation, and stroke recorded in National Health Service files through November 2022.

Brighter nights showed dose-response associations with higher risk across all five outcomes. Participants classified in the 90–100th percentile of night-time light exposure experienced 23–32% higher hazard for coronary artery disease, 42–47% for myocardial infarction, 45–56% for heart failure, 28–32% for atrial fibrillation, and 28–30% for stroke compared with those in the 0-50th percentile.

Women displayed stronger associations for heart failure and coronary artery disease whereas younger participants showed stronger associations for heart failure and atrial fibrillation.

Authors propose circadian misalignment induced by unnatural light may trigger metabolic and vascular perturbations that elevate cardiovascular risk. Impaired glucose tolerance and heightened diabetes susceptibility may foster endothelial dysfunction and atherosclerosis.

Light-driven hypercoagulability could increase thromboembolic events, while sustained elevation of 24-hour blood pressure may damage vascular endothelium and provoke myocardial hypertrophy. Conflicting timing signals to sinoatrial and atrioventricular nodes may amplify arrhythmic vulnerability.

Avoiding bright light during habitual sleep times may serve as a practical addition to established cardiovascular prevention strategies.

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TOPICS: Health/Medicine
KEYWORDS: cardiac; circadianrythms; disease; heart; light; sleep; unnaturallight

[ConservativeMind]

It is very important to truly block as much light as possible, during sleep, to maintain your health.

I have used eye masks when the room I was sleeping in had light. I also turn any lit clock away from me and rely on my wristwatch for time (which has luminescent watch arms). I use my cell phone for my alarm.

Also, don’t use a night light.

[ConservativeMind]

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[Organic Panic]

Let me guess. Night lights are racist too.

[Bob434]

If you need a night light because you have to get up several times a night for various reasons. They do have led adjustable nightlight. You can set it very low with just enough light to illuminate the room Just enough to avoid tripping over items. We have a couple to help prevent falls.

[bunkerhill7]

I just light a bonfire in the middle of the room.

[maro]

You can also get motion triggered night lights.

[bunkerhill7]

There is no survey for before the light bulb was invented so it’s a farce because of a lack of a control.

[Cold Heart]

This is where an out of work climate change scientist could come up with the missing survey.

[Bob434]

Ah good idea- those would be even better.

[madison10]

I cover all the little electronic type lights in my bedroom, some with tape. I cannot sleep with any light at ALL, but electronic light is worse than incandescent light.

There would be no sleep with light.

[vpintheak]

Well, Alaskans are screwed.

[NaturalScience]

"I have used eye masks when the room I was sleeping in had light. I also turn any lit clock away from me and rely on my wristwatch for time (which has luminescent watch arms). I use my cell phone for my alarm."

I just sleep with my eyes closed.

[sauropod]

.

[Bob434]

You weirdo lol 🤣

[Salamander]

I need a light due to imbalance/vertigo issues.

If the electricity goes off and plunges me into darkness,I have to freeze wherever I am and slowly try to feel my way to a flashlight, struggling to not fall over from dizziness the whole time

My inner ear doesn’t function for maintaining balance anymore and I rely solely on vision to remain vertical.

I have no choice in this matter

I really miss my PTSD/balance dog because he knew to race to my side and lean against me to keep me from falling.

I now have more flashlights than you can imagine and always have one in easy reach by my bed just in case.

😑

[Diana in Wisconsin]

At this point in time, my BLADDER controls my ‘circadian rhythms.’ ;)

Our house is pitch, and I mean PITCH BLACK if there are no nightlights. ‘Can’t see your hand in front of your face,’ type of dark. Totally unsafe for me and mine.

I don’t have a nightlight in the bedroom, but in the adjoining bathroom, for the reason stated above.

Beau can sleep through a nuclear war, so I’m not worried about him...yet! ;)

[nagant]

Light rhythm rules the pineal gland. The pineal gland rules the release cycle of melatonin. Melatonin cycles rule insulin release, and the rhythms of the orexin nervous system. The orexin nervous system governs the release of many enzymes and hormones.