A new study investigates the effects of near-infrared radiation (NIR) in ambient indoor lighting on human cognitive performance, emotional state, and cardiovascular health. The research addresses the absence of NIR in modern electric lighting systems and energy-efficient windows, despite its biological activity and therapeutic applications.

In a preregistered within-subjects double-blind experiment, 151 university students (117 females, 34 males) were exposed to two lighting conditions during a 2-hour laboratory session. Both conditions included 3500 K white LED light, but one condition additionally incorporated NIR (875 nm, 960 nm) and far-red (735 nm) wavelengths.

Key findings:

Cardiovascular effects:

• Beneficial effects on resting high-frequency heart rate variability (HF-HRV)
• Improved HF-HRV responses to cognitive demand

Emotional effects:

• Enhanced feelings of pleasure

Cognitive effects:

• Reduced performance on a visual search task

The researchers hypothesized that:

• Cognitive performance would improve under NIR-rich lighting across various domains (attention, perception, short-term memory, working memory, and executive function).
• Mood would improve under NIR-rich lighting, reflected in higher ratings of pleasure, alertness, and environmental satisfaction.
• Cardiovascular function would be modulated by NIR exposure, with differences in resting HF-HRV and improved HF-HRV responses to cognitive demand.

The study’s findings reveal that the absence of NIR in architectural lighting influences humans at both psychological and physiological levels. This has implications for health and well-being that need to be balanced against energy-saving considerations.

Background

NIR constitutes approximately 50% of solar radiation reaching Earth’s surface. Modern electric light sources, including LEDs, typically exclude NIR emission as an energy-saving measure. However, NIR exposure has recognized therapeutic effects through photobiomodulation, with applications in wound healing, inflammation reduction, pain relief, eye health improvement, neurological condition treatment, cognitive function enhancement, and psychological well-being promotion.

Methodology

The experiment employed a within-subjects design with two counterbalanced lighting conditions:

1. Normal fractional amount of NIR typical in daylight
2. Nearly zero NIR, as in conventional LED lighting

Participants were monitored at rest and while engaged in cognitively demanding tasks during each condition.

Implications

This study is the first to examine the influence of ambient NIR in indoor lighting on cognitive, emotional, and cardiovascular levels. The results suggest that the exclusion of NIR from indoor environments may have unintended consequences for human health and well-being. These findings highlight the need to consider the biological effects of lighting when designing energy-efficient indoor environments.

The published study can be found here.

Image: Pexels.com

David Shiller

David Shiller is the Publisher of LightNOW, and President of Lighting Solution Development, a North American consulting firm providing business development services to advanced lighting manufacturers. The ALA awarded David the Pillar of the Industry Award. David has co-chaired ALA’s Engineering Committee since 2010. David established MaxLite’s OEM component sales into a multi-million dollar division. He invented GU24 lamps while leading ENERGY STAR lighting programs for the US EPA. David has been published in leading lighting publications, including LD+A, enLIGHTenment Magazine, LEDs Magazine, and more.

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