Are you one of those people who can’t sleep if even a tiny sliver of light slips under the door? Or do you doze best with the glow of the TV in the background? Or a nightlight?

While there’s no shame in needing some twinkling comfort, in the case of sleep, darkness might be more important than most of us realize. A recent study revealed that even low levels of light while you sleep could be silently raising your heart attack risk. Specifically, researchers tracked nearly 90,000 adults over the course of nine years and discovered that those with the brightest bedrooms were at a 42% higher risk of a heart attack than those in dark rooms.

This striking difference held true even after accounting for genetics, lifestyle factors like diet, exercise, smoking and other daily habits that affect heart health.

Experts suggest that light at night might disrupt circadian rhythms — our internal body clocks — which regulate sleep, blood pressure and heart health. Even subtle interference can put extra stress on the cardiovascular system, slowly raising the risk of serious cardiovascular events over time.

Fortunately, small adjustments can make a real difference. Dimming bedroom lights, turning off electronic devices, covering screens or installing blackout curtains can all help protect your circadian rhythm and give your heart a better chance to stay healthy.

Reducing nighttime light exposure might be a simple, low-cost and highly effective way to support both long-term heart health and deeper, more restorative sleep.

So to sleep tight, sleep dark. Your heart is happiest when the lights are out.