Non-motor symptoms including reduced sleep efficiency and excessive daytime sleepiness are common in people with Parkinson’s disease. These symptoms often precede or contribute to worsening of motor symptoms. While studies using different methodologies of bright light delivery have shown beneficial effects of light on sleep and motor behavior, the pathomechanisms as to why light is effective are not known, the proof of concept is required to provide clinical recommendations for light therapy.
Light, as the primary driver of circadian function and sleep, is transmitted by melanopsin expressing photoreceptors in the eye to the central body clock in the brain to regulate release of the dark hormone (melatonin) and modulate sleep and wakefulness. Our team made two fundamental discoveries concerning the mechanism through which light affects people with PD. We first discovered that melanopsin cells are dysfunctional in people with early PD (Joyce, Feigl, Kerr, Roeder, Zele 2018). Our second discovery was that melanopsin dysfunction contributes to sleep disruption (supporting preliminary data).
Our aim is to demonstrate the positive effect of melanopsin-directed lighting on non-motor (sleep and circadian) and motor (gait, balance, tremor) symptoms. In the morning or evening during 4-weeks, people with PD will view our new lighting technology that generates light which preferentially increases or decreases melanopsin activity in the eye. Because both lights have the same (white) appearance, we can use a study design where both the investigators and participants are unaware of their light treatment condition. We will quantify melanopsin cell function using non-invasive methods (pupillometry) established in our laboratory and monitor sleep and motor behaviors before and after light intervention.
Our ultimate goal is to provide the justification and recommendations for home application of melanopsin-directed lighting to help PD sufferers to self-regulate and improve non-motor and motor symptoms, hence improve their quality of life.
