Bright light improves alertness in night driving, says Canadian study

By GEORGE WONG | 15 June 2015

SEATTLE: As you drive into the night, turn on a bright light to improve your performance, suggests a new study that says doing this could improve cognition and alertness.

This extends to night-shift workers whose work environment is dimly lit, for bright light suppresses the release of the natural sleep hormone melatonin, according to the researchers.

While this does not improve subjective alertness or coordination, it staves off the effects of sleep deprivation and, as the hours pass, bright light works better than dim light at enhancing your alertness.

In the study, the researchers screened would-be participants to find out their circadian rhythm chronotype, a scientific expression for whether you like to go to bed early and wake up early or if you prefer the opposite.

They also screened them for sleep disorders and propensity for motion sickness because a driving simulator was the vehicle for the experiment.

They accepted a total of 19 mostly-male participants whose mean age was 23 and structured the experiment in a crossover design involving repeated measures.

Conditions for testing included having not experienced sleep deprivation within a week of driving the simulated circuit.

Participants were asked to stay awake until they exhibited sleep deprivation and 45 minutes later the research team exposed them to either dim light or bright light.

Next, they were asked to drive in the simulator for 45 minutes, divided into two circuits of at least 22 minutes each.

Being sleep deprived, they experienced telltale consequences that could have led to accidents in a real-life driving situation, and the incidents worsened as the task continued.

Bright light did not make much of a difference when compared to dim light until after the first 22-minute circuit; however, it made a significant, positive difference in the next, reducing would-be-accidents, according to the study.

"We were most surprised to find that significant differences between the bright light condition and the dim light condition occurred in the second lap of the simulated driving task rather than immediately following the bright light exposure," says lead author Denise Weisgerber, a doctoral candidate at Simon Fraser University in Burnaby, British Columbia, Canada.

Weisgerber says the experience of driving in a simulator might have aroused participants, thereby masking the effects of bright light during the first circuit.

The study was presented on June 9 in Seattle, Washington in the US at SLEEP 2015, the 29th annual meeting of the Associated Professional Sleep Societies LLC.