Men more sensitive to blue light
Sensitivity to blue-enriched light is influenced by sex differences, such that males display a stronger response even to very low light levels, a recent study suggests. Moreover, sex differences also affect the acute benefits of bedtime blue light exposure such as sustained attention.
In the study, 32 participants (mean age 25.2±3.1 years; 50 percent female) were subjected to 1.5 hours of dim light (<8 lx), 2 hours of darkness, 2 hours of light exposure (40 lx) and 45 minutes of dim light (<8 lx), in sequence, until habitual sleep time. Both groups were matched according to age, ethnicity and body mass index.
Males preferred the 40-lx light delivered by a 6,500-K than by a 2,500-K fluorescent lamp (62.5 vs 37.5 percent). An opposite trend was observed for females (12.5 vs 87.5 percent, respectively), with the difference between the sexes reaching significance (p=0.004).
In a posthoc analysis, males were found to perceive the 6,500-K light as significantly stronger than the 2,500-K light (mean, 85.6±4.5 vs 67.7±5.4).
Light condition, specifically the 6,500-K light, significantly improved the median response time (p<0.005) and 10-percent fastest response time (p<0.001) exclusively in males. No such effect was observed in females.
Moreover, following exposure to 6,500-K light before bedtime, males had significantly higher frontal nonrapid eye movement slow-wave activity (2 to 4 Hz) sleep electroencephalogram power density than women (p<0.05).
“Collectively, the data indicate that sex differences in light sensitivity might play a key role for ensuring the success of individually-targeted light interventions,” said researchers.