Effects of daytime exposure to different monochromatic lights on the excretion of 6-sulfatoxymelatonin (aMT6s) in a hospital environment

ABSTRACT

Hospitalized patients are frequently deprived of contact with natural light and constantly exposed to artificial lighting, losing biological synchronism. However, few studies have been conducted to assess the consequences of inadequate exposure to light in hospital environments, whether related to insufficient light in the period daytime, or to light peaks at night. This study assesses the effect of daytime exposure to different monochromatic lights on the excretion of 6-sulfatoxymelatonin (aMT6s), a hormone that reflects variations in the light/dark cycle. The light intensity was adjusted to 300 lx. Forty voluntary patients under transfusion were randomly assigned into five groups of light exposure for five hours, during the day. The concentration of aMT6s was determined in the urine samples collected at four intervals in a period of 24 hours during two days (before and at intervention). Exposure to green light resulted in significant acute melatonin reduction; blue light, in delay of night secretion; red, yellow and white light, kept it unaltered. These findings indicate that exposure to light during the day can lead to changes in the pattern of melatonin secretion. This research can be useful in artificial lighting environments, such as hospitals, to maintain adequate lighting and preserve the sleep/wake cycle.

KEYWORDS:

• Light
• melatonin
• circadian rhythm

Authors’ contributions

T.G.C.A. and E.Z.M. designed the research. T.G.C.A. performed the research. E.Z.M. performed data analyses. All authors wrote the paper and reviewed the manuscript.

Disclosure statement

The authors report no conflict of interest.

Ethics approval and informed consent

This study was approved by the research ethics committee of the University Hospital of the Ribeirão Preto Medical School at the University of São Paulo (CAAE 16,924,213.9.0000.5440) and was conducted in accordance with the Declaration of Helsinki. All participants have given written informed consent to take part in the study.