Effects of differences in the availability of light upon the circadian rhythms of institutionalized elderly

The aim of this study was to compare the availability of diurnal and nocturnal light in two residences for aged persons (R1 and R2, Palma de Mallorca, Illes Balears, Spain). We found that the R1 inmates were exposed to lower amounts of light during waking time and higher amounts during sleeping time. The main traits of the circadian rhythms and the quality of sleep in the inmates of the two residences were found to be positively related to the availability of light during waking time and negatively to the increased light exposure during bed time. In addition, the sleep of R1 inmates suffered higher disturbances as a consequence of the different policy for nocturnal diapers check and change. Altogether, these two factors may explain the differences observed in the two residences regarding the circadian rhythms, health status and quality of life. Two conclusions stem from these results: (1) the circadian rhythms of aged people are particularly sensitive to the contrast between diurnal and nocturnal light and (2) the nursing staff of institutions for aged people must receive specific formation on the best practices for maintaining the circadian health of aged people.