Shift work affects approximately 15% of workers in industrialized nations and increases cardiovascular disease (CVD) risk, including coronary heart disease (CHD), beyond lifestyle or socioeconomic factors. These risks are primarily driven by circadian misalignment, which occurs when the internal clock is out of sync with the sleep-wake cycle. Laboratory studies using forced desynchrony and stimulated shift work protocols have shown elevated blood pressure and reduced cardiac vagal activity during misalignment. Although shift work persists, effective interventions are lacking. Preclinical findings suggest that aligning food intake with the circadian cycle supports heart health.
A recent study published in Nature Communications aimed to explore whether restricting food intake to daytime can reduce the adverse effects of circadian misalignment compared to eating during day and night using secondary analysis of data from clinical trial NCT02291952.
In a single-blind, parallel-arm clinical trial, 20 healthy non-shift workers (mean age = 26.6±4.2 years, male = 12, female = 8, body mass index [BMI] = 18.5–29.9 kg/m2, hemoglobin A1C range: 4.9–5.4%) were randomized into either a Nighttime Meal either a Group (NMC) or Daytime Meal Intervention Group (DMI). NMC participants (n = 10, mean age = 27±4.4 years, female = 4, BMI = 22.5±3.5 kg/m2) consumed meals during both the day and night, whereas DMI participants (n = 9, mean age = 26.2±4.1 years, female = 3, BMI = 23.1±3.1 kg/m2) consumed meals during the daytime.
The primary endpoints were heart rate variability, including the percentage of successive normal-to-normal (NN) intervals that differ by more than 50 milliseconds (pNN50), Root Mean Square of the Successive Differences (RMSSD), Low Frequency to High Frequency (LF/HF) ratio, electrocardiogram (ECG). The secondary endpoint was the plasminogen activator inhibitor-1 (PAI-1) concentration. Exploratory endpoints were heart rate, concentration of cortisol, and blood pressure. All these outcomes were measured before (baseline) and after (post misalignment) stimulated night workers under constant routine (CR) settings.
In cosinor mixed-model analysis revealed that the meal timing intervention significantly modified the effect of simulated night work on pNN50 (positive false discovery rate [pFDR] = 0.008), RMSSD (pFDR = 0.02) and PAI-1 (pFDR = 0.02) between meal timing group and pre/post simulated night work interaction. In NMC group, the levels of pNN50 reduced by 25.7% (95% confidence interval (CI) of −33.9% to −17.5%; P = 0.001), RMSSD decreased significantly by 14.3% (95% CI, −18.4% to −10.1%; P = 0.001), LF/HF ratio levels increased significantly by 5.5% (95%CI, 3.5% to 6.9%; P = 0.03) and PAI-1 levels enhanced significantly by 23.9% (95%CI, −2.3% to −45.6%; P = 0.001) after simulated night work compared to baseline. Whereas in DMI group, no significant difference was found on pNN50 (95% CI of −8.9% to 4.9%; P = 0.23), RMSSD (95% CI, −2.1% to 2.2%; P = 0.31), LF/HF ratio (95% CI, −0.3% to 1.7%; P = 0.29) and PAI-1 (95% CI, −2.1% to 2.2%; P = 0.24).
In explaining outcomes, the intervention significantly altered the effect of simulated night work on systolic blood pressure (SBP) and diastolic blood pressure (DBP) levels with P = 0.03 and P = 0.02, respectively.
Tukey-Kramer post-hoc test adjusted for multiple comparisons, the levels of SBP and DBP did not significantly difference in NMC after simulated night work compared to baseline (SBP: 95% CI, −1.3% to 2.8%; DBP: 95% CI, −1.1% to 0.7, P = 0.22). While blood pressure levels significantly reduced in the DMI group by 6-8% (SBP: −6.1%, 95% CI, −8.9% to −4.5%; DBP: −8.0%, 95% CI, −9.1% to −6.9%; Tukey-Kramer post-hoc test adjusted for multiple comparisons, P = 0.005 and P = 0.001).
In cosinor mixed-model analysis, meal timing intervention did not significantly alter the effect of simulated night work on heart rate (P = 0.51), cortisol (P = 0.45), SBP (P = 0.31), and DBP (P = 0.34).
This study’s limitations include young participants, small sample sizes, lack of actual shift workers, and limited real-world applicability of the forced desynchrony (FD) protocol.
In conclusion, this study results suggest that eating during the day even with mistimed sleep may help reduce the adverse cardiovascular risks caused by circadian misalignment, providing translational evidence for the development of behavioral approaches to protect shift workers.
Reference: Chellappa SL, Gao L, Qian J, et al. Daytime eating during simulated night work mitigates changes in cardiovascular risk factors: secondary analyses of a randomized controlled trial. Nat Commun. 2025;16:3186. doi:10.1038/s41467-025-57846-y
