Juliane Hannemann1, Anika Laing1, Benita Middleton2, Jonathan Cridland3, Bart Staels4, Nikolaus Marx5, Peter J Grant6, Massimo Federici7, Tarja Stenberg8, Debra J Skene2, Rainer Böger1. 1. Institute of Clinical Pharmacology and Toxicology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany. 2. Sleep, Chronobiology and Addiction Research Group, University of Surrey, Guildford, Surrey, England. 3. Outside In (Cambridge) Ltd., Cambridge, UK. 4. University of Lille, Inserm, CHU Lille, Institut Pasteur de Lille, U1011- EGID, Lille, France. 5. Department of Cardiology, University Medical Center Aachen, Aachen, Germany. 6. Leeds Institute of Cardiovascular and Metabolic Medicine, University of Leeds, Leeds, UK. 7. Center for Atherosclerosis, University of Rome 'Tor Vergata' School of Medicine, Rome, Italy. 8. Institute of Biomedicine/Sleep Research Group, University of Helsinki, Finland.
Abstract
OBJECTIVES: Night shift work is associated with high rates of hypertension and cardiometabolic disease, which are linked to disrupted circadian rhythms. We hypothesized that timed light therapy might improve disrupted circadian rhythms and stabilize diurnal control of blood pressure and glucose in night shift workers. METHODS: We randomized 24 rotating night shift workers (mean age, 36 ± 13 years, 7 men) who had spent a median of 6 years on rotating night shifts (median, six night shifts per month) to 12 weeks of light therapy or no intervention and compared them with 12 daytime workers (37 ±11 years, 6 men). We measured oral glucose tolerance (OGTT), 24-h blood pressure and arterial stiffness, and the circadian profiles of melatonin, cortisol, metanephrine and nor-metanephrine at baseline, after 12 weeks of intervention, and 12 weeks after the end of intervention. RESULTS: At baseline, fewer night shift workers showed dipper status as compared with daytime workers (29 vs. 58%; P < 0.001). After 12 weeks of light therapy, there was a highly significant increase in the proportion of dippers (to 58%; P < 0.0001). We also observed a significant decrease in serum glucose during OGTT in the light therapy group (-22%; P < 0.05) with no change in serum insulin. Whilst circadian profiles of melatonin and cortisol were unchanged, plasma metanephrine and nor-metanephrine levels were significantly reduced in the light therapy group (P < 0.01). CONCLUSION:Timed light therapy improves diurnal blood pressure control and glucose tolerance in rotating night shift workers. This effect is unrelated to melatonin and cortisol but is paralleled by reduced catecholamine levels.
RCT Entities:
OBJECTIVES: Night shift work is associated with high rates of hypertension and cardiometabolic disease, which are linked to disrupted circadian rhythms. We hypothesized that timed light therapy might improve disrupted circadian rhythms and stabilize diurnal control of blood pressure and glucose in night shift workers. METHODS: We randomized 24 rotating night shift workers (mean age, 36 ± 13 years, 7 men) who had spent a median of 6 years on rotating night shifts (median, six night shifts per month) to 12 weeks of light therapy or no intervention and compared them with 12 daytime workers (37 ± 11 years, 6 men). We measured oral glucose tolerance (OGTT), 24-h blood pressure and arterial stiffness, and the circadian profiles of melatonin, cortisol, metanephrine and nor-metanephrine at baseline, after 12 weeks of intervention, and 12 weeks after the end of intervention. RESULTS: At baseline, fewer night shift workers showed dipper status as compared with daytime workers (29 vs. 58%; P < 0.001). After 12 weeks of light therapy, there was a highly significant increase in the proportion of dippers (to 58%; P < 0.0001). We also observed a significant decrease in serum glucose during OGTT in the light therapy group (-22%; P < 0.05) with no change in serum insulin. Whilst circadian profiles of melatonin and cortisol were unchanged, plasma metanephrine and nor-metanephrine levels were significantly reduced in the light therapy group (P < 0.01). CONCLUSION: Timed light therapy improves diurnal blood pressure control and glucose tolerance in rotating night shift workers. This effect is unrelated to melatonin and cortisol but is paralleled by reduced catecholamine levels.