Effects of timed physical exercise on arterial stiffness in night shift workers

Background: Night shift workers have a higher incidence of cardiovascular and cardiometabolic diseases. Indeed, frequent to chronic disruption of the circadian rhythm promotes arterial stiffening, which is associated with cardiovascular diseases and negatively influenced by lack of physical activity, smoking, a proatherogenic diet and aging. Since regular physical activity is generally cardioprotective it was the aim of this study to assess whether physical exercise training before each night shift exerts comparable effects on markers of cardiovascular risk. This trial is part of the European wide study, called EuRhythDia, analyzing the influence of different kinds of interventions on the circadian rhythm in night shift workers (EU-project, study coordination University Medical Center Hamburg-Eppendorf ). Methods: Normotensive night shift workers from Salzburg (n = 57; median age 35 (21–57) years) were enrolled and randomized into an intervention (IG, n = 47) or a control (CG, n = 10) group. Subjects in the intervention group but not in the control group performed 35 minutes of high intensity interval training on cycle ergometers not longer than 2 hours before each night shift (≥4/month) for 12 weeks. All subjects were followed for further 12 weeks without structured exercise training. At baseline, 12 and 24 weeks arterial stiffness parameters, e. g. central systolic blood pressure (cSBP), central pulse pressure (cPP), augmentation index corrected for heart rate of 75 bpm (AIx@75), reflection coefficient, amplitude of the backward- (Pb) and of the forward pressure wave (Pf ) as well as the pulse wave velocity (PWV) were measured non-invasively by oscillometry. Results: After 12 weeks of exercise training, all parameters of arterial stiffness but the reflection coefficient were significantly improved (p < .05). No significant effects were examined in the control group. Gender correlated with the reflection coefficient in both groups (IG, r = 0.455, p < .01, CG, r = 0.922, p < .001), where values in women (–3.1%) but not men (+3.1%) decreased. Furthermore, in the intervention group there was a negative correlation between age, cPP and Pf. Within the control group, smoking correlated negatively with cPP, Pf and PWV (all p < .05). Conclusions: High intensity interval training no longer than 2 hours before night shift work improves arterial stiffness already after 12 weeks of training. Greater responses correlated with the number of exercise training sessions. Our data demonstrate for the first time that exercise training before night shift work can lead to an improvement in cardiovascular risk.