Abstract
Objectives: Evening blue light has been shown to suppress melatonin, which can negatively impact sleep quality. The impact of evening blue light blocking (BLB) interventions on sleep remains ambiguous due to lack of randomized control trials. The present study tests the hypothesis that BLB glasses improve subjective and objective sleep in a population of healthy adults.
Design: Two-week, randomized, controlled, crossover design.
Setting: At-home testing of individuals in Michigan and Montana.
Participants: Twenty healthy adults (11 men, 9 women, age: 32 ± 12, body mass index: 28 ± 4 kg/m2).
Intervention: Following a 1-week run-in baseline (ie, no glasses), participants were randomized to 1-week of BLB or control (ie, clear lens) glasses. Upon finishing the 1-week intervention, participants crossed over to the opposite condition. In both conditions, glasses were worn for 7 consecutive days from 6 PM until bedtime.
Measurements: Objective sleep parameters were obtained using wrist actigraphy. Subjective sleep measures were assessed using sleep diaries. Karolinska Sleep Diaries were used to assess perceived sleep quality.
Results: BLB reduced subjective sleep onset (21 ± 28 vs 24 ± 21 minute, P = .033) and awakenings (1.6 ± 1.0 vs 2.2 ± 1.0 awakenings, P = .019) compared to the control condition. In contrast, objective measures of sleep were not significantly impacted. In fact, our primary outcome variable of total sleep time (TST) tended to be paradoxically shorter in the BLB condition for both subjective (468 ± 45 vs 480 ± 48 minute, P = .066) and objective (433 ± 40 vs 449 ± 39 minute, P = .075) TST.
Conclusions: Blue light blocking glasses did not improve objective measures of sleep time or quality in healthy adults.
https://pubmed.ncbi.nlm.nih.gov/33707105/
