Effect of dynamic light at the coronary care unit on the length of hospital stay and development of delirium: a retrospective cohort study

Background Disturbed circadian rhythm is a potential cause of delirium and is linked to disorganisation of the circadian rhythmicity. Dynamic light (DL) could reset the circadian rhythm by activation of the suprachiasmatic nucleus to prevent delirium. Evidence regarding the effects of light therapy is predominantly focused on psychiatric disorders and circadian rhythm sleep disorders. In this study, we investigated the effect of DL on the total hospital length of stay (LOS) and occurrence of delirium in patients admitted to the Coronary Care Unit (CCU). Methods This was a retrospective cohort study. Patients older than 18 years, who were hospitalized longer than 12 h at the CCU and had a total hospital LOS for at least 24 h, were included. Patients were assigned to a room with DL (n = 369) or regular lighting conditions (n = 379). DL was administered at the CCU by two ceiling-mounted light panels delivering light with a colour temperature between 2700 and 6500 degrees Kelvin. Reported outcome data were: total hospital LOS, delirium incidence, consultation of a geriatrician and the amount of prescripted antipsychotics. Results Between May 2015 and May 2016, data from 748 patients were collected. Baseline characteristics, including risk factors provoking delirium, were equal in both groups. Median total hospital LOS in the DL group was 100.5 (70.8–186.0) and 101.0 (73.0–176.4) h in the control group (P = 0.935). The incidence of delirium in the DL and control group was 5.4% (20/369) and 5.0% (19/379), respectively (P = 0.802). No significant differences between the DL and control group were observed in secondary endpoints. Subgroup analysis based on age and CCU LOS also showed no differences. Conclusion Our study suggests exposure to DL as an early single approach does not result in a reduction of total hospital LOS or reduced incidence of delirium. When delirium was diagnosed, it was associated with poor hospital outcome.