We meticulously plan our diets, our exercise routines, and our sleep schedules, all in the pursuit of better health. But what if one of the most powerful tools for influencing our well-being has been hiding in plain sight, bathing our rooms in a generic glow we’ve long taken for granted? That was the central theme of WAC Group’s recent webinar, part of our educational series created in partnership with the Light and Health Research Center (LHRC) at the Icahn School of Medicine at Mount Sinai.

According to experts from the LHRC, the light we live in has a profound and measurable impact on everything from our mood and alertness to our sleep quality and long-term health. In a detailed discussion led by Patrick Laidlaw of WAC Group, in conjunction with the LHRC’s Director, Dr. Mariana Figueiro, and Program Director, Jennifer Brons, the science behind Human-Centric and Circadian Rhythm Lighting was brought to light. This isn’t “snake oil,” they assert, but a field grounded in decades of research, offering practical solutions that can transform our built environments, from homes and offices to healthcare settings.

For most of history, we’ve thought of lighting in one dimension: visibility. But lighting has a dual role. It affects our visual system, allowing us to see and perceive our environment, but it also impacts a powerful so-called “non-visual” system that governs our internal biological clock, or circadian rhythm.

“From a scientific perspective, every type of lighting is human-centric because it enables us to see in our environment, affects our perceptual system, and influences how we perceive and feel in a space,” the experts explain. This connection even taps into our biophilia—our innate desire to be close to nature. Daylight, with its dynamic changes in light level and color, provides stability and cues that help us orient ourselves.

The “non-visual” effects are where the science gets truly fascinating. In our retinas, our photoreceptors are not just dedicated to sight, but they also send signals to the brain’s biological clock. Light acts as a powerful stimulant with a direct, acute effect on the brain, much like a cup of coffee. The right kind of light exposure can make you more alert at any time of day. However, for regulating your 24-hour biological clock, the timing of that light is crucial.

The foundation for this science was laid decades ago. A groundbreaking 1980 study by researcher Al Lewy revealed that electric light at night suppresses the production of melatonin, the hormone that signals nighttime to the body and prepares our body for rest. In the early 90’s work led by Dr. Russell Foster in England, showed that blind mice responded to light for the circadian system. In the early 2000s, Dr. David Berson and his team at Brown University, discovered a new class of photoreceptors in the eye that are highly influential on our biological clock. The LHRC’s research focuses on how the retina combines signals from all these types of photoreceptors to regulate our circadian rhythms.

In today’s world, we live in a “muted” light environment. Inside the built environment, our days aren’t always bright enough, and our nights aren’t always dark enough. This lack of contrast confuses our biological clocks, leading to issues like difficulty sleeping, morning grogginess, and even long-term health problems like diabetes and obesity.

The solution, according to Laidlaw and the LHRC, is elegantly simple. The circadian system is always looking for two things: contrast and regularity. This translates into a powerful, actionable framework they call the “trifecta” of healthy lighting:

• Bright Days: Expose yourself to high levels of light, especially in the morning and throughout the day.
• Dim Evenings: Gradually step down light levels for at least two hours before bedtime.
• Dark Nights: Ensure your sleeping environment is as dark as possible to allow for robust melatonin production and restorative sleep.

Achieving this contrast requires regularity. “We joke that a healthy life is a boring life because you’re doing the same thing every day at the same time,” the researchers note. Waking up at the same time, getting morning light exposure, and winding down consistently reinforces a strong, healthy circadian system. They offer a memorable analogy: getting a puppy. It forces you to wake up at the same time every day and go outside into the daylight—an ideal scenario for entrenching a healthy routine.

So, how can you implement these principles at home? The good news is that it doesn’t require a complete overhaul. It’s about being strategic.

The Morning Boost: To achieve bright days, especially if you work from home, you need to actively increase your light exposure. The LHRC recommends a half-hour walk outdoors every day, preferably in the morning, which will help keep your biological clock in synch. Indoors, you can achieve this by:

• Adding Layers of Light: Instead of relying on a single overhead fixture, use multiple sources—ceiling lights, wall sconces, and task lamps—to raise the overall light level.
• Using Higher Output: The LHRC’s own studies utilize portable lamps with outputs of 3000 to 4000 lumens in the morning, softening the light with diffusers to prevent uncomfortable glare.
• Strategic Placement: Place portable lamps closer to you to increase the light reaching your eyes without having to illuminate the entire room to an intense level (a concept based on the inverse square law of light).

The Evening Wind-Down: This is just as critical as the morning boost.

• Dim Down: Use dimmers to lower the light levels of your provided by your fixtures. Sophisticated control systems can do this automatically based on the time of day, but a simple dimmer switch is a great start.
• Warm Up: While not required, as you dim the lights, you can shift to warmer colors. “Dim to Warm” technology mimics the gentle, amber glow of old-fashioned incandescent bulbs, which can have a psychological effect, signaling it’s time to relax.
• Avoid Glare: Glare, or excessive brightness shining directly into your eyes, is uncomfortable and disruptive. This is especially true as we age. To reduce glare, choose fixtures with a high cutoff or regressed LEDs that shield the light source from direct view.

The market is now flooded with products claiming to be “circadian lighting.” This has created confusion, particularly around the role of spectrum (color) of light. The experts at LHRC offer a clear hierarchy of importance:

• Timing and Amount: Getting bright light at the right time and dim light at the right time is paramount.
• Application: How and where the light is delivered is more important than the product itself.
• Spectrum (Color): Color does have an impact, but it’s a third-level effect. Timing and amount are more important to consider. For example, you can achieve circadian-effective light with a warm color bulb if it is bright enough.

Our circadian system is most sensitive to short-wavelength (blue) light. This is true. Because of this sensitivity, you need a slightly lower amount of bluish white light to activate the system than a warmer, yellowish white light. However, it does not mean that warmer, yellower light has no effect. It is still effective; you just need a bit more of it.

This nuance is where many products and applications fail. The researchers shared a compelling example of a nursing home that installed an expensive, tunable lighting system. The system could change color and light level, checking all the “circadian” boxes. Yet, it failed to deliver circadian effective light at the eye. Why? It was designed for horizontal illuminance—lighting the desks and floors for visibility. It failed to deliver enough vertical illuminance—light to the residents’ eyes.

“The system wasn’t effective, not because it was flawed, but because it wasn’t designed accordingly,” they stress. A “circadian bulb” in a ceiling can be useless if not enough of its light reaches the person’s eyes. This is why communicating these principles to architects, designers, and homeowners is so vital.

And what about the constant barrage from our screens? The advice is simple: look away regularly to reduce eye fatigue. As for blue-light filtering glasses, the jury is still out. “Nobody knows if it works because you really need to perform the measurements to see what it filters and what it doesn’t,” the experts caution. The most effective strategy is to reduce screen brightness, reverse polarity of the screen (i.e., use black background) or avoid them altogether in the couple of hours before bed.

The science of healthy lighting is not about selling a product; it’s about improving people’s health. The most difficult struggle we face is our constant connection to screens and our muted indoor environments.

But the solutions are within our reach. By focusing on the core principles of contrast (bright days, dim evenings, dark nights) and regularity, we can passively and seamlessly improve our sleep and well-being. Think of it like taking a pill for better health—a simple, consistent action you take every morning and evening. Whether through a basic dimmer switch, a walk in the sun, or a well-designed lighting plan, the power to harness light for a healthier, more vibrant life is truly in our hands.

Watch The Webinar Here: Light And Health | WAC Lighting

Subject Matter Experts:

Mariana Figueiro, Ph.D., Professor and Director

Jennifer Brons, M.S., Program Director

Light and Health Research Center, Icahn School of Medicine at Mount Sinai

Host:

Patrick Laidlaw, Director of Business Development – Integration, WAC Group