The influence of blue light on sleep, performance and wellbeing in young adults: A systematic review

Electronic devices emitting blue light are now ubiquitous and have been linked to reduced sleep quality via melatonin suppression and circadian rhythm disruption. Yet, evidence also suggests potential positive effects of blue light on mood, cognition, and performance. The research question of this systematic review was to synthesize evidence on how blue light exposure influences sleep, performance, and wellbeing in healthy humans and to discuss its relevance for athletes, who rely on optimal sleep, alertness, and cognitive function.

Prior systematic reviews have focused on specific outcomes of light exposure, such as circadian rhythm (Tähkämö et al., 2019), macular health (Lawrenson et al., 2017), mental disorders (Srisurapanont et al., 2021), or tumors (Lai and Yew, 2016). To the authors' knowledge, no systematic review has comprehensively examined blue light’s influence on sleep, performance, and wellbeing in healthy humans or athletes. This review addresses that gap by aggregating findings across these domains.

The review followed PRISMA guidelines. Databases searched included Cochrane, Embase, PubMed (with human filter), Scopus, and the Virtual Health Library on September 27, 2020. A compound search strategy combined four clusters (blue light, sleep, performance, wellbeing) with AND operators; related terms were connected with OR. Eligibility included randomized controlled trials, cohort, case-control, and cross-sectional studies in English on healthy humans, assessing blue light exposure effects on sleep, performance, wellbeing, or combinations thereof. Studies focusing on participants with health issues or only on circadian phase/melatonin were excluded. Screening removed duplicates, then titles/abstracts (488 records identified; 78 full texts assessed; 8 added via references; 36 studies included). Data extracted included participant age, activity during exposure, intervention type, exposure duration, measurement tools, study design, and outcomes. Quality assessment used the QualSyst tool (Kmet et al., 2004) across 14 items, scored 0–2 or N/A, with studies categorized as strong (>75%), moderate (55–75%), or weak (<55%). Two reviewers (MS, CP) performed quality assessment, resolving discrepancies by consensus. Of the 36 studies, 24 were strong quality and 12 moderate.

Sleep: Tiredness-related measures showed mixed but often beneficial effects; across 20 occurrences, 10 indicated decreased tiredness with blue light, 7 no change, and 3 increases. Sleep quality: of 5 studies, 1 decreased (Burkhart and Phelps, 2009), 1 increased (Viola et al., 2008), 3 no change. Sleep duration: 3/9 decreased (Münch et al., 2016; Yang et al., 2018; Chindamo et al., 2019), 1/9 increased (Viola et al., 2008), 5 no change. Sleep efficacy: 2/4 decreased (Ayaki et al., 2016; Yang et al., 2018), 2 no change. Sleep latency: 3/8 increased (Ayaki et al., 2016; Chang et al., 2015; Chindamo et al., 2019), 5 no change. Performance: Cognitive performance increased in 4/7 studies (An et al., 2009; Motamedzadeh et al., 2017; Viola et al., 2008 work performance; Taillard et al., 2012 driving), with others showing no change in specific contexts. Alertness: 7 of 10 occurrences reported increases (including sustained attention, concentration, reduced omission errors); 2 no change; 1 increase in commission errors next morning after evening exposure. Reaction time: 9/13 studies showed decreases (improvements) with blue light (including Lockley et al., 2006; Phipps-Nelson et al., 2009; Münch et al., 2016; Motamedzadeh et al., 2017; Yang et al., 2018), with some null findings and one subgroup effect (blue-eyed participants). Accuracy: increased in 1 study (Heath et al., 2014), 3 no change. Heart rate: increased under both blue and red vs dark in one study; no next-morning change in another. Handgrip strength: no effect. Wellbeing: Mood increased in 2 studies (Viola et al., 2008; Ekström and Beaven, 2014), decreased in 1 (Burkhart and Phelps, 2009), no change in 1 (Gabel et al., 2013). Irritability decreased in 1 study. Arousal: energetic arousal increased in 1, others no change for tense arousal/hedonic tone/subjective arousal. Tension and anxiety: no significant effect in 1 study. Motivation to exercise and perceived exertion next day: no effect. Overall proportional summary from abstract: about 50% of studies reported decreased tiredness; ~20% decreased sleep quality; ~33% decreased sleep duration; ~50% decreased sleep efficacy; slightly less than half increased sleep latency; >50% increased cognitive performance; slightly >66% increased alertness and decreased reaction time; slightly <50% increased wellbeing.

Blue light exposure frequently improves cognitive performance, alertness, and reaction time, suggesting practical benefits for athletes in sports requiring rapid decision-making, teamwork, and vigilance, potentially aiding injury prevention. Conversely, blue light can negatively affect aspects of sleep (e.g., decreased sleep quality and duration, increased sleep latency or decreased efficacy), which may impair recovery and performance if exposure occurs close to bedtime. The balance between leveraging alertness and performance gains and protecting sleep health is critical. Measurement tools in the included studies ranged from validated questionnaires (e.g., KSS, PANAS) and objective tasks (e.g., PVT, Go/NoGo, n-back), though heterogeneity and reliance on self-report in some domains warrant cautious interpretation. More targeted research in athletic contexts is needed to clarify dose, timing, and modality of blue light that maximize benefits while minimizing sleep-related detriments.

Blue light exposure can positively influence cognitive performance, alertness, and reaction times, offering potential advantages in sports requiring quick cognition and vigilance, and possibly contributing to injury prevention through heightened alertness and wellbeing. However, it may also reduce sleep quality and duration and alter sleep timing, with potential negative impacts on performance and recovery. Further research should determine optimal timing, dosing, and application methods of blue light to enhance athletic performance without compromising sleep, and explore mechanistic links among sleep, performance, and wellbeing.

Most included participants were healthy adults (typically 20–30 years), with only three studies involving athletes. Outcomes were sometimes grouped under umbrella terms (e.g., tiredness), and exposures predominantly occurred during non-strenuous, non-athletic tasks, leaving effects under physical stress and hormonal influences uncertain. The influence of mental health on wellbeing and performance, and interactions among sleep, performance, and wellbeing were not fully assessed. Heterogeneity in study designs, measurement tools, and exposure modalities limits generalizability. The impact of nocturnal blue light exposure during sleep (e.g., phone use at night) remains unaddressed and warrants investigation.