Key Project Outcomes
Delayed sleep-wake phase disorder (DSWPD) is a circadian rhythm sleep-wake disorder characterized by a significant delay in sleep-wake timing with respect to the environmental light-dark schedule. In non-24 hour sleep-wake disorder (N24SWD) individuals exhibit a progressive daily delay in circadian rhythms. While this has previously been identified in blind individuals, thought to be secondary to a lack of light perception, this disorder has also been described in sighted individuals, but the underlying cause in this case unclear. In both DSWPD and sighted N24SWD one proposed mechanism underlying these disorders is that these individuals exhibit an impaired ability to respond to the circadian effects of light. It is known that the circadian response to light is mediated by cells in the retina containing a photopigment called melanopsin.
The aim of this study was to determine whether melanopsin dependent phototransduction was impaired in patients with DSWPD and sighted N24SWD. Seventeen patients with sighted N24SWD, 12 patients with DSWPD and 21 control subjects were recruited to undergo pupillometry testing. Results demonstrated that individuals with sighted N24SWD had an impaired melanopsin dependent response to light when compared to either those with DSWPD or controls. This suggests that while these individuals have normal imaging forming vision, they may be blind to the circadian effects of light, contributing to their inability to entrain to the environmental light dark schedule.
Melanopsin-dependent phototransduction is impaired in delayed sleep–wake phase disorder and sighted non–24-hour sleep–wake rhythm disorder