Is cardiovascular autonomic control during the day‐to‐night transition dependent on dim light melatonin onset? An exploratory analysis in healthy adults

Figures

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  FIGURE 1. Ultra‐short semi‐constant study protocol. After confirming study eligibility. Participants remained seated in a comfortable chair for the next 7 h. Data collection started 6 h before the self‐selected bedtime (vertical dashed line), which participants had followed for 7 days before the visit. Light blue drops represent salivary samples collected every 30 min. Black triangles represent 10‐min recordings of resting ECG and beat‐to‐beat blood pressure, obtained every 1 h. The white shaded area represents room lighting at 150 lux; and the gray shaded area represents dim light wake periods below 8 lux.

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  FIGURE 2. Mean difference between dim‐light melatonin onset (DLMO) and the onset time of each cardiovascular (CV) index. Mean values are plotted with their respective thresholds of significance for each index, which were determined by employing one‐sample t‐tests sequentially compared with absolute decimal increments representing an interval of 10 min (i.e., versus 0.1, 0.2, 0.3, etc.) until a p‐value <0.05. Negative thresholds of significance mean CV onset occurred before DLMO while positive values mean after DLMO. R‐R interval (RR‐I); Root of the mean of the sum of the squares of differences between adjacent NN intervals (RMSSD); Low‐frequency and high‐frequency ratio of RR‐I variability (LF/HFR‐R); systolic blood pressure (SBP); and Low‐frequency SBP variability (LFSBP).

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  FIGURE 3. Pearson correlation between the difference of dim‐light melatonin onset (DLMO) and shift onset time of R‐R interval (R‐Ri) and bedtime (panel a); R‐Ri and mispoint sleep (panel b); square root of the mean of the sum of the squares of differences between adjacent NN intervals (RMSSD) and phase angle (panel c); low to high‐frequency ratio of R‐Ri variability (LFHFR‐Ri) and phase angle (panel d); systolic blood pressure (SBP) and phase angle (panel e); and low‐frequency of SBP variability (LF SBP) and phase angle (panel f). Considering an adjusted p‐value using Benjamini‐Hochberg's false discovery rate correction. Numbers represent the same participant in every scatter plot.