LED Flicker: Myth or Genuine Health Risk?

The Invisible Flicker of LED Lights: Myth or Genuine Risk?

The lights flicker. The question is whether this flickering, invisible to the eye, can affect health. The discussion has intensified: while some dismiss any effect, others point to headaches and visual fatigue. What is true? The answer is that, like almost everything else, it depends on the product quality and individual sensitivity.

Why LED Bulbs Flicker

The majority of LED bulbs flicker at 100-120 Hz. The cause is twofold: on one hand, the AC power from the grid (50 Hz in Spain) is rectified, but if it is not filtered correctly, the sawtooth wave produces a flicker at double the frequency, i.e., 100 Hz. On the other hand, dimmers use Pulse Width Modulation (PWM) to vary brightness, chopping the current into bursts. Both effects are imperceptible to the human eye, but not to a camera: just point your phone at a bulb and you can see moving bands.

The IEEE 1789 standard addresses this phenomenon. It recommends that, at 100-120 Hz, the flicker percentage should be less than 8% to consider it low risk, and below 3% to completely eliminate its effects. Many cheap bulbs do not meet this threshold.

Does it Affect Health?

The proponents of the risk theory cite headaches, cognitive decline, anxiety, and vision problems. Individuals with electrosensitivity claim they cannot tolerate this flickering. From a scientific point of view, the effect on most people is nil, but there is no consensus regarding absolute safety: some studies associate prolonged exposure to low frequencies with eye fatigue and headaches, especially in sensitive individuals.

The key lies in the driver (the transformer powering the LED). A quality driver maintains low ripple, whereas low-end capacitive assemblies produce noticeable flicker. It is argued that the problem is minor today, but faulty lamps where flickering is visible even in videos are still sold.

The Irony of Incandescents

Those who advocate returning to old-fashioned bulbs forget that they also flicker. The 50 Hz AC current generates waves that turn off twice per cycle, i.e., at 100 Hz. The difference is that the tungsten filament, being incandescent, has a thermal inertia that doesn't allow it time to cool down and emit intermittent light. The flicker exists, but it is masked. Some say this is more natural, although the physics are the same.

LEDs Everywhere

This entire discussion becomes somewhat absurd when we realize that LED technology is everywhere: monitors, televisions, phones, cars. The screen you are reading this article on also emits flickering light. Isolating the living room bulb doesn't help much if you spend hours in front of a screen that also modulates at low frequencies. Only technological Luddites who reject every device made after 2010 can escape partially, although not even they escape urban 5G.

Meanwhile, the cheapest solution remains to turn off the light and look at your phone, which keeps flickering. If you are truly concerned, invest in quality bulbs with low flicker certification. Otherwise, you always have candles.