Eating only during daytime is associated with significant modifications in cardiovascular risk factors under simulated night work conditions.
The meal timing intervention resulted in no significant changes in cardiac measures or prothrombotic factors in the Daytime Meal Intervention Group.
In the Nighttime Meal Control Group, there were observed decreases in percentage consecutive heartbeat intervals (>50 ms) by 25.7% and root mean square of successive heartbeat differences by 14.3%.
An increase in low/high cardiac frequency ratio by 5.5% and in plasminogen activator inhibitor-1 by 23.9% was recorded in the Control Group postmisalignment compared to baseline.
Blood pressure showed a significant reduction of 6-8% in the Intervention Group, with no significant changes in the Control Group.
Heart rate and cortisol levels did not show significant effects related to the meal timing intervention.
Simplified
Effective countermeasures against the adverse cardiovascular effects of circadian misalignment, such as effects experienced due to night work or jet lag, remain to be established in humans. Here, we aim to test whether eating only during daytime can mitigate such adverse effects vs. eating during the night and day (typical for night shift workers) under simulated night work (secondary analysis of NCT02291952). This single-blind, parallel-arm trial randomized 20 healthy participants (non-shift workers) to simulated night work with meals consumed during night and day (Nighttime Meal Control Group) or only during daytime (Daytime Meal Intervention Group). The primary outcomes were (percentage consecutive heartbeat intervals >50 ms), RMSSD (root mean square of successive heartbeat differences), and LF/HF (low/high cardiac frequency). The secondary outcome was blood concentrations of prothrombotic factor plasminogen activator inhibitor-1 (). These measures were assessed under Constant Routine conditions, before (baseline) and after (postmisalignment) simulated night work. The meal timing intervention significantly modified the impact of simulated night work on cardiac vagal modulation and PAI-1 (pFDR = 0.001). In the Control Group, the postmisalignment Constant Routine showed a decrease in pNN50 by 25.7% (pFDR = 0.008) and RMMSD by 14.3% (pFDR = 0.02), and an increase in LF/HF by 5.5% (pFDR = 0.04) and PAI-1 by 23.9% (pFDR = 0.04), vs. the baseline Constant Routine. In the Intervention Group, there were no significant changes in these outcomes. For exploratory outcomes, the intervention significantly modified the impact of simulated night work on blood pressure (P < 0.05), with no significant change in the Control Group, and a significant reduction by 6-8% (P < 0.01) in the Intervention Group; without significant effects for heart rate or cortisol. These findings indicate that daytime eating, despite mistimed sleep, may mitigate changes in cardiovascular risk factors and offer translational evidence for developing a behavioral strategy to help minimize the adverse changes in cardiovascular risk factors in individuals exposed to circadian misalignment, such as shift workers.
Key numbers
25.7%
Decrease in
Change in cardiac vagal modulation in the Nighttime Meal Control Group post-simulated night work.
23.9%
Increase in
Change in prothrombotic factor in the Nighttime Meal Control Group post-simulated night work.
6-8%
Blood pressure reduction
Decrease in blood pressure in the Daytime Meal Intervention Group post-simulated night work.
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Competing interests: F.A.J.L.S. served on the Board of Directors for the Sleep Research Society and has received consulting fees from the University of Alabama at Birmingham and Morehouse University. F.A.J.L.S. interests were reviewed and managed by Brigham and Women’s Hospital and Partners HealthCare in accordance with their conflict-of-interest policies. F.A.J.L.S. consultancies are not related to the current work. The other authors declare that they have no competing interests.
