Effect of a light-darkness cycle on the body weight gain of preterm infants admitted to the neonatal intensive care unit

Abstract

The Continuous bright light conditions to which premature infants are subjected while hospitalized in Neonatal Intensive Care Units (NICU) can have deleterious effects in terms of growth and development. This study evaluates the benefits of a light/darkness cycle (LDC) in weight and early hospital discharge from the NICU. Subjects were recruited from three participating institutions in Mexico. Eligible patients (n = 294) were premature infants who were hospitalized in the low-risk and high-risk neonatal units classified as stable. The subjects randomized to the experimental group (n = 150) were allocated to LDC conditions are as follows: light from 07:00 to 19:00 and darkness (25 lx) from 19:00 to 07:00. The control group (n = 144) was kept under normal room light conditions (CBL) 24 h a day. Main outcome was weight gain and the effect of reducing the intensity of nocturnal light in development of premature infants. Infants to the LDC gained weight earlier, compared with those randomized to CBL, and had a significant reduction in length of hospital stay. These results highlight those premature infants subjected to a LDC exhibit improvements in physiological development, favoring earlier weight gain and consequently a decrease in hospital stays. ClinicalTrials.gov; 02/09/2020 ID: NCT05230706.

Figure 1

(A) Daily milk consumption in both study groups. Infants allocated to the experimental study group tolerated more milliliters in the initial days post-birth compared with subjects in the control group. The difference between daily milk consumption between study groups was statistically significant (*p < 0·001). (B) Body weight gain among infants included in each study group, there is a numerical difference since the first 7 days, but this difference is statistically significant 10 days after birth (*p < 0·001). White circles (open circle) represent the control group (CBL), while black circles (filled circle) represent the experimental group (LDC).

Figure 2

Average salivary melatonin levels; (A) For subjects allocated to the CBL group, there is no difference in average melatonin during light and darkness phases. (B) Subjects allocated to the LDC had a statistically significant difference in terms of average melatonin during day and night sample acquisition, this difference was identified since day 6 post-birth (p < 0·0001).

Figure 3

Average length of hospital stays (NICU) among subjects randomized to the control (CBL) and experimental (LDC) study groups. Patients allocated to the control group had a statistically significant prolonged hospital stay (*p < 0·001).

Figure 4

(A) Representative images of infants randomized to CBL (left panels) and LDC (right panels). (B) Illumination level (measured in Lux mean ± SD) during different conditions in the NICU, including daytime, nighttime, and when using the cephalic helmet for infants randomized to the LDC study group (*p-value < 0·002; + p-value < 0·001 when comparing with the illumination level while wearing the cephalic helmet); (the authors have the consent of the parents of the patients to publish the photographs).