Circadian system functional status and sleep in blind subjects with and without conscious light perception

To understand circadian rhythms and sleep in an understudied population, which is particularly prone to suffer chronodisruption (CD), eighteen blind volunteers of 51.5 ± 3.6 years (Mean ± SEM) and 26 volunteers (51.8 ± 1.2) with no visual impairments wore the ambulatory circadian monitoring (ACM) device Kronowise^® for seven consecutive days in real-life conditions. Nine of the blind participants declared to have some sort of light perception while the other nine declared to lack conscious light perception. ACM combines measurements of distal skin temperature; motor activity, light exposure and feeding schedules, providing information about lifestyle and the bidirectional crosstalk between internal time and external synchronisers, which is paramount to determine a subject's CD degree. We found a extraordinarily diverse population in terms of blindness aetiology and thus, in the degree of affectation of the participants visual and circadian systems. Our results pointed to poorer circadian health and sleep in the blind participants, which could be directly related to the impact of disease over circadian photoreception but also to disruption of daily habits. Compared to controls, blind participants showed significantly lower light exposure and physical activity values during the day and higher time of movement during the night. Besides, we analysed feeding schedules in the blind participants for the first time and found that their last meal of the day happened later than in controls, thus blind participants' night fasting was shorter. Altogether, our results indicated substantial behavioural circadian alterations associated with the disease.