Acute night shift work is associated with increased blood pressure and reduced sleep duration in healthy adults

Abstract

Shift workers have a 40% higher risk for cardiovascular disease (CVD) compared to people who work day shifts. However, the acute impact of shift work on CVD risk factors in free-living settings remains unclear. We therefore investigated the impact of acute night shift work on factors related to cardiovascular health including blood pressure (BP) and sleep duration. Twenty-four rotating shift workers (19F, 23 ± 4 y, BMI: 23 ± 3 kg/m²; mean ± SD) participated in a quasi-randomized crossover study. Assessments were conducted over the course of 1 day shift and one night shift in a free-living setting. BP was measured every 30 min by an ambulatory monitor. Sleep and wake times were recorded. Mixed effects models were conducted to examine changes in variables between conditions. Acute night shift work was associated with significantly higher 24 h systolic (107 ± 1 vs. 104 ± 1 mmHg; p < 0.0001) and diastolic (67 ± 1 vs. 64 ± 1 mmHg; p < 0.0001) BP, as well as blunted dipping patterns in systolic BP (8 ± 1 vs. 12 ± 1%; p = 0.032), as compared to day shift work. Sleep duration was significantly shorter during the night shift as compared to the day shift (4 h 04 ± 19 min vs. 8 h 22 ± 18 min; p < 0.0001). As little as one night of shift work in a free-living setting is sufficient to induce multiple CVD risk factors including increased BP and reduced sleep duration in healthy adults. It is critical to identify strategies to prevent or attenuate the negative impact of shift work on CVD risk in a large portion of the working population.

Keywords: ambulatory blood pressure; blood pressure dipping; cardiovascular disease; free‐living; shift work.

FIGURE 1

Overview of experimental protocol. Data collection was conducted in a quasi‐randomized crossover order under free‐living conditions for two work shifts including a day shift (top; a) and a night shift (bottom; b). SBP, DBP, and HR were recorded every 30 min as represented by the blue dotted line. The gray rectangle indicates the mean self‐reported sleep period during day shift ± SEM. The red rectangle indicates the mean self‐reported sleep period during night shift ± SEM.

FIGURE 2

Systolic blood pressure (left; a), diastolic blood pressure (middle; b) and heart rate (right; c) readings assessed every 30 min during each condition and analyzed by mixed‐effects model. Data are presented as least square means ± SEM. The gray rectangle indicates the mean self‐reported sleep period during day shift ± SEM. The red rectangle indicates the mean self‐reported sleep period during night shift ± SEM. *p value <0.05.

FIGURE 3

Individual blood pressure dip (a and b) and surge (c and d) responses to day shift versus night shift work. Blood pressure dip was calculated as the percent change from mean waking to mean sleeping blood pressure. Blood pressure surge was calculated as the absolute difference between the mean blood pressure from the 2 h before to the 2 h after waking up. Individual responses indicated by the solid lines; mean responses for each outcome are indicated by the dashed lines. Data were analyzed using mixed‐effects models. *p value <0.05.