The Effect of Photobiomodulation on Sleep Architecture in Warfighters — USU Research Days 2023
Penafiel A, Metzger E, Hager N, Wagner L, Isaacson B, Pasquina P, Werner K
Abstract accepted for a poster session at the 2023 USU Research Days
The average sleep quality in the military is so poor that the cutoff in validated subjective sleep quality complaint measures is twice as high as that in civilians. More than two-thirds of the military report sleeping less than the recommended seven hours per night. This sleep restriction (SR) can lead to reduced reaction time, verbal fluency, working and visual memory, and information processing, all of which are key functions in the completion of military activities. SR can also lead to atrophy of hippocampal subregions and other long term neurobehavioral consequences. The current mechanisms to combat SR, including caffeine, psychostimulants, and exercise, have varying effectiveness and short-lived results; therefore, an intervention with long-lasting effects is needed.
Photobiomodulation therapy (PBMT) is a non-invasive intervention that applies non-ionizing light to the body to enhance performance, stimulate healing, moderate recovery, and improve health. Red/infrared PBMT (e.g. 600-900 nm) is known to be absorbed by cytochrome c oxidase within the mitochondria, facilitating electron transfer efficiency and doubling adenosine triphosphate production in cells. PBMT delivered via intranasal applicators, diode lasers, and/or light treatment helmet devices has been shown to penetrate the skin and skull, resulting in modulated brain activity. One study utilized electroencephalography (EEG) to measure the effects of transcranial PBMT (tPBMT) on neural oscillations. tPBMT modulated oscillatory frequencies for delta, theta, alpha, beta, and gamma bands, as well as affected the power and functional connectivity of internal brain activity. Additionally, tPBMT using near infrared light has been shown to potentially improve cognitive function, attention, and executive function, supporting its use in neurological interventions.
Two placebo-controlled studies have examined the effect of PBMT on sleep in athletes after dosing the whole body with multiple short exposures. One study using noncoherent red light with a wavelength of 685nm dosed at 30 J/cm2 was associated with improved subjective sleep quality, increased total sleep time, and decreased sleep onset latency. They also demonstrated the PBMT group had a significant increase in morning serum melatonin. Conversely, a separate study found that PBMT dosed at 14.4 J/cm2 with an irradiance of 0.012W/cm2 decreased total sleep time but increased the percentage of N2 and N3 sleep, while improving sleep quality. The mechanisms of efficacy remain unclear. While neither study examined objective measures of brain activity during wake or sleep, we hypothesize that brain exposure to PBMT will optimize energetics for the coordinated firing involved in the deepest "slow-wave" sleep, yielding increased power in the delta band and improved sleep quality. This abstract provides the methods and expected outcomes of our study that will explore the application of PBMT in a military sample to characterize the effects of this modality on sleep.