Scientific Reports: Bright Light Helps the Brain Stay Alert During Night Shifts

Bright light may help the brain maintain attention and alertness during nighttime work, according to a meta-analysis published in the journal Scientific Reports.

Scientists analyzed the results of 16 studies involving 311 people that examined the effects of light therapy on cognitive function under conditions designed to simulate night shifts. Participants were exposed to bright light ranging from 1,056 to 10,000 lux, while control groups were exposed to significantly dimmer lighting.

Overall, participants performed better on cognitive tests after exposure to bright light than those in the control groups. The most noticeable effects were seen in alertness, attention, and reaction speed.

In studies that assessed participants directly during light exposure, bright light improved overall cognitive performance as well as executive functions—the ability to concentrate, process information, and perform complex tasks.

Some effects also persisted after the light exposure. In particular, alertness and attention improved, as did reaction speed. The effects were especially noticeable in tests of psychomotor vigilance—the ability to respond quickly to emerging signals, which is particularly important during nighttime work.

However, the researchers identified an interesting detail: more light did not necessarily mean better results. The longer the total duration of light exposure before testing, the weaker some of the beneficial effects became.

The authors also found a possible inverted U-shaped relationship, suggesting that moderate exposure may be more effective than excessive exposure. However, this finding remains a hypothesis and does not yet make it possible to determine the optimal light dose.

The researchers emphasize that the findings cannot yet be directly applied to all night-shift workers. Most participants were young, with an average age of about 24, and 78% were men. In addition, only six of the 16 studies were randomized controlled trials, and the experimental conditions did not always reflect real-world nighttime work.

Nevertheless, the findings suggest that properly designed bright lighting may help maintain attention and alertness during nighttime work. Further research is needed to determine the optimal light intensity, timing, and duration of exposure.