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Comparison of Coronary Microcirculation in Female Nurses After Day-Time Versus Night-Time Shifts

2011; Elsevier BV; Volume: 108; Issue: 11 Linguagem: Inglês

10.1016/j.amjcard.2011.07.028

1879-1913

Tomoichiro Kubo, Shota Fukuda, Kumiko Hirata, Kenei Shimada, Kumiko Maeda, Kenichi Komukai, Yasushi Kono, Reiko Miyahana, Koki Nakanishi, Kenichiro Otsuka, Satoshi Jissho, Haruyuki Taguchi, Minoru Yoshiyama, Takashi Akasaka, Junichi Yoshikawa,

Climate Change and Health Impacts

Nightshift work, which is known to cause mental stress and disrupt normal biological diurnal rhythms, leads to endothelial dysfunction resulting in increased risk for cardiovascular disease. This study aimed to investigate the acute effect of night-shift work on coronary microcirculation through assessment of coronary flow reserve (CFR) by transthoracic Doppler echocardiography. This study consisted of 36 women nurses who underwent transthoracic Doppler echocardiographic examinations after working a nightshift and on a regular day without previous nightshift work. Flow velocity in the distal portion of the left anterior descending coronary artery was measured at baseline and during adenosine infusion. CFR was calculated as the ratio of hyperemic to basal mean diastolic flow velocity. CFR after night work was lower than that on a regular workday (3.8 ± 0.6 vs 4.1 ± 0.6, p <0.001). Degree of decreases in CFR after night work was correlated to Framingham risk score (r = 0.35, p = 0.036). In conclusion, this study demonstrated that coronary microcirculation was impaired after nightshift work in women nurses. Nightshift work, which is known to cause mental stress and disrupt normal biological diurnal rhythms, leads to endothelial dysfunction resulting in increased risk for cardiovascular disease. This study aimed to investigate the acute effect of night-shift work on coronary microcirculation through assessment of coronary flow reserve (CFR) by transthoracic Doppler echocardiography. This study consisted of 36 women nurses who underwent transthoracic Doppler echocardiographic examinations after working a nightshift and on a regular day without previous nightshift work. Flow velocity in the distal portion of the left anterior descending coronary artery was measured at baseline and during adenosine infusion. CFR was calculated as the ratio of hyperemic to basal mean diastolic flow velocity. CFR after night work was lower than that on a regular workday (3.8 ± 0.6 vs 4.1 ± 0.6, p 30 kg/m2). Framingham risk score was then calculated.14Wilson P.W. D'Agostino R.B. Levy D. Belanger A.M. Silbershatz H. Kannel W.B. Prediction of coronary heart disease using risk factor categories.Circulation. 1998; 97: 1837-1847Crossref PubMed Scopus (7608) Google Scholar The study was approved by the institutional review board of each participating institution. Written informed consent for participation was obtained from each subject. TTDE was performed using a Sequoia 512 (Siemens Medical Solutions, Mountainview, California) or a Vivid 7 (GE Medical Systems, Milwaukee, Wisconsin) as previously described.15Hozumi T. Yoshida K. Ogata Y. Akasaka T. Asami Y. Takagi T. Morioka S. Noninvasive assessment of significant left anterior descending coronary artery stenosis by coronary flow velocity reserve with transthoracic color Doppler echocardiography.Circulation. 1998; 97: 1557-1562Crossref PubMed Scopus (380) Google Scholar, 16Caiati C. Montaldo C. Zedda N. Bina A. Iliceto S. New noninvasive method for coronary flow reserve assessment: contrast-enhanced transthoracic second harmonic echo Doppler.Circulation. 1999; 99: 771-778Crossref PubMed Scopus (304) Google Scholar Coronary blood flow velocity in the distal portion of the left anterior descending coronary artery coronary artery was estimated at baseline and after intravenous infusion of adenosine triphosphate (ATP) at a rate of 140 μg/kg per minute for 2 minutes to produce hyperemia. CFR was calculated as the ratio of hyperemic to basal mean diastolic flow velocity (MDFV). Values were expressed as mean ± SD. Comparisons of laboratory and echocardiographic data between 2 time points were made with paired t test. Linear regression analysis was used for correlation of variables of interest. Differences in hemodynamics and transthoracic Doppler echocardiographic results after ATP infusion between the 2 time points were evaluated by 2-way repeated-measures analysis of variance testing for group effect (2 different times), ATP effect, and interaction. Differences were considered statistically significant at a p value <0.05. All subjects had no history of cardiovascular disease and none were taking any medications except for hypercholesterolemia in 1 subject, smoking in 8 subjects, and hypercholesterolemia and smoking in 1 subject. These subjects did not receive contraceptive hormonal therapy. Mean body mass index was 20.9 ± 3.4 kg/m2. All subjects had normal results on their echocardiographic examinations. Average duration of nightshift work was 7.6 ± 6.1 years (range 0.1 to 23) and mean number of nightshifts per month was 5.4 ± 1.9 times the level observed at the start of the study. Table 1, Table 2 present baseline hemodynamic and laboratory results, respectively. Because young nurses working the nightshift were enrolled in this study, mean Framingham risk score was low (−10.4 ± 5.6, range −16 to 1).Table 1Hemodynamics and echocardiographic results on regular workday and after nightshift workVariableRegular WorkdayAfter Nightshift WorkOverall p Value⁎Interaction of nightshift work with adenosine triphosphate effect by 2-way repeated-measures analysis of variance.Heart rate (beats/min) Baseline69 ± 1067 ± 90.5 Adenosine triphosphate infusion73 ± 1073 ± 10Systolic blood pressure (mm Hg) Baseline101 ± 13101 ± 110.8 Adenosine triphosphate infusion97 ± 1197 ± 13Mean diastolic flow velocity (cm/s) Baseline0.17 ± 0.040.16 ± 0.040.06 Adenosine triphosphate infusion0.67 ± 0.180.60 ± 0.15 Interaction of nightshift work with adenosine triphosphate effect by 2-way repeated-measures analysis of variance. Open table in a new tab Table 2Laboratory data on regular workday and after nightshift workVariableRegular WorkdayAfter Nightshift Workp ValueLeukocyte count (/mm3)6,079 ± 18866,013 ± 19000.8High-sensitive C-reactive protein (mg/dl)0.082 ± 0.110.089 ± 0.130.5Total cholesterol (mg/dl)184 ± 24183 ± 290.7Low-density lipoprotein cholesterol (mg/dl)100 ± 2099 ± 250.6High-density lipoprotein cholesterol (mg/dl)67 ± 1467 ± 140.9Triglyceride (mg/dl)70 ± 3465 ± 430.3Glucose (mg/dl)96 ± 1292 ± 70.1Estradiol (pg/ml)119 ± 118102 ± 1110.4Cortisol (μg/dl)11 ± 510 ± 30.3Norepinephrine (pg/ml)238 ± 170235 ± 1680.8Epinephrine (pg/ml)31 ± 3631 ± 200.9 Open table in a new tab Results of CFR measurements are summarized in Figure 1. CFR was lower after nightshift work than on a regular workday. Values of MDFV before and after ATP infusion at 2 different time points are listed in Table 1. Two-way analysis of variance showed no significant interaction in MDFV between the 2 groups during ATP infusion. Table 1, Table 2 present results of hemodynamics and laboratory tests, respectively. There were no significant interactions in heart rate and systolic blood pressure between the 2 groups during ATP infusion. There was no significant difference in any laboratory variable between the 2 time points. Ten subjects who had hypercholesterolemia and/or smoking tended to have larger decreases of CFR after nightshift work than other subjects (−0.48 ± 0.38 vs −0.23 ± 0.47, p = 0.1). Degree of decreases in CFR after nightshift work was correlated to Framingham risk score as shown in Figure 2. There were no significant relations between degree of decreases in CFR after night work and other clinical and laboratory parameters (Table 3).Table 3Relation between degree of decreases in coronary flow reserve after night work and clinical and laboratory resultsVariablerp ValueAge0.010.9Duration of nightshift work0.040.8Number of nightshifts per month0.020.9Body mass index0.200.2Systolic blood pressure0.060.7Leukocyte count0.050.8High-sensitive C-reactive protein0.10.5Total cholesterol0.320.05Low-density lipoprotein cholesterol0.310.06High-density lipoprotein cholesterol0.040.8Triglyceride0.040.8Glucose0.030.9Estradiol0.080.6Cortisol0.20.2Norepinephrine0.050.8Epinephrine0.10.6 Open table in a new tab The present study demonstrated for the first time that coronary microcirculation was impaired after nightshift work in medical personnel. There is increasing evidence for the detrimental effects of shift work on health status, in particular cardiovascular disease, and other chronic diseases. Epidemiologic studies have reported increased risk of cardiovascular disease in shift workers.1Olsen O. Kristensen T.S. Impact of work environment on cardiovascular diseases in Denmark.J Epidemiol Community Health. 1991; 45: 4-9Crossref PubMed Scopus (79) Google Scholar, 2Kawachi I. Colditz G.A. Stampfer M.J. Willett W.C. Manson J.E. Speizer F.E. Hennekens C.H. Prospective study of shift work and risk of coronary heart disease in women.Circulation. 1995; 92: 3178-3182Crossref PubMed Scopus (404) Google Scholar Amir et al12Amir O. Alroy S. Schliamser J.E. Asmir I. Shiran A. Flugelman M.Y. Halon D.A. Lewis B.S. Brachial artery endothelial function in residents and fellows working night shifts.Am J Cardiol. 2004; 93: 947-949Abstract Full Text Full Text PDF PubMed Scopus (77) Google Scholar and our group13Shimada K. Fukuda S. Maeda K. 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In the absence of epicardial coronary narrowing CFR is considered a physiologic index of coronary microcirculation. Because of its noninvasive, relatively inexpensive, and physiologic nature, TTDE has been used to evaluate serial changes in CFR for several cardiovascular risk factors including hyperglycemia,19Fujimoto K. Hozumi T. Watanabe H. Tokai K. Shimada K. Yoshiyama M. Homma S. Yoshikawa J. Acute hyperglycemia induced by oral glucose loading suppresses coronary microcirculation on transthoracic Doppler echocardiography in healthy young adults.Echocardiography. 2006; 23: 829-834Crossref PubMed Scopus (24) Google Scholar hyperlipidemia,20Hozumi T. Eisenberg M. Sugioka K. Kokkirala A.R. Watanabe H. Teragaki M. Yoshikawa J. Homma S. Change in coronary flow reserve on transthoracic Doppler echocardiography after a single high-fat meal in young healthy men.Ann Intern Med. 2002; 136: 523-528Crossref PubMed Scopus (40) Google Scholar and smoking.21Otsuka R. Watanabe H. Hirata K. 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"Passive exercise" using whole body periodic acceleration: effects on coronary microcirculation.Am Heart J. 2010; 159: 620-626Crossref PubMed Scopus (25) Google Scholar has been also demonstrated with TTDE. We demonstrated that nightshift work aggravated coronary microcirculation in women nurses. Taking into account that working night shifts simultaneously cause sleep and mental problems, the result of this study is consistent with previous observations. Sekine et al25Sekine T. Daimon M. Hasegawa R. Toyoda T. Kawata T. Funabashi N. Komuro I. The impact of sleep deprivation on the coronary circulation.Int J Cardiol. 2010; 144: 266-267Abstract Full Text Full Text PDF PubMed Scopus (16) Google Scholar investigated the influence of sleep deprivation on coronary microcirculation and demonstrated that CFR after approximately 4 hours of sleep was lower than that after 7 hours of sleep. Furthermore, temporary mental stress has been reported to decrease flow-mediated dilation26Ghiadoni L. Donald A.E. Cropley M. Mullen M.J. Oakley G. Taylor M. O'Connor G. Betteridge J. Klein N. Steptoe A. Deanfield J.E. Mental stress induces transient endothelial dysfunction in humans.Circulation. 2000; 102: 2473-2478Crossref PubMed Scopus (546) Google Scholar and CFR.27Hasegawa R. Daimon M. Toyoda T. Teramoto K. Sekine T. Kawata T. Watanabe H. Kuwabara Y. Yoshida K. Komuro I. Effect of mental stress on coronary flow velocity reserve in healthy men.Am J Cardiol. 2005; 96: 137-140Abstract Full Text Full Text PDF PubMed Scopus (10) Google Scholar Our recent study demonstrated that 30-minute aromatherapy alleviated peripheral endothelial dysfunction of medical staff after nightshift work, suggesting that concomitant mental stress was also enough to cause impairment of CFR after nightshift work.13Shimada K. Fukuda S. Maeda K. Kawasaki T. Kono Y. Jissho S. Taguchi H. Yoshiyama M. Yoshikawa J. Aromatherapy alleviates endothelial dysfunction of medical staff after night-shift work: preliminary observations.Hypertens Res. 2011; 34: 264-267Crossref PubMed Scopus (20) Google Scholar A similar transient disorder of the coronary microcirculation was observed in association with several risk factors including hyperglycemia,19Fujimoto K. Hozumi T. Watanabe H. Tokai K. Shimada K. Yoshiyama M. Homma S. Yoshikawa J. Acute hyperglycemia induced by oral glucose loading suppresses coronary microcirculation on transthoracic Doppler echocardiography in healthy young adults.Echocardiography. 2006; 23: 829-834Crossref PubMed Scopus (24) Google Scholar hypertriglyceridemia,28Vogel R.A. Corretti M.C. Plotnick G.D. Effect of a single high-fat meal on endothelial function in healthy subjects.Am J Cardiol. 1997; 79: 350-354Abstract Full Text Full Text PDF PubMed Scopus (680) Google Scholar and smoking.29Giannini D. Leone A. Di Bisceglie D. Nuti M. Strata G. Buttitta F. Masserini L. Balbarini A. The effects of acute passive smoke exposure on endothelium-dependent brachial artery dilation in healthy individuals.Angiology. 2007; 58: 211-217Crossref PubMed Scopus (45) Google Scholar Such transient but repetitive endothelial dysfunction could potentially promote the early stages of atherosclerosis and the development of cardiovascular disease. Furthermore, negative effects of nightshift work might be additive or synergistic in the presence of underlying cardiovascular diseases. There were several limitations to this study. First, the study population was relatively small (n = 36). Thus, the impact of the intensity/accumulation of nightshifts on results of this study was unclear. Further study of a larger population with long-term follow-up should be performed to confirm the results of the present study. Second, the transthoracic Doppler echocardiographic method allows measurement of coronary flow velocity without estimation of coronary artery diameter. In fact, CFR derived from changes only in coronary flow velocity was used in previous large invasive studies.30Serruys P.W. de Bruyne B. Carlier S. Sousa J.E. Piek J. Muramatsu T. Vrints C. Probst P. Seabra-Gomes R. Simpson I. Voudris V. Gurné O. Pijls N. Belardi J. van Es G.A. Boersma E. Morel M.A. van Hout B. Doppler Endpoints Balloon Angioplasty Trial Europe (DEBATE) II Study GroupRandomized comparison of primary stenting and provisional balloon angioplasty guided by flow velocity measurement.Circulation. 2000; 102: 2930-2937Crossref PubMed Scopus (103) Google Scholar Third, because CFR was measured immediately after nightshift work, further investigation is necessary to clarify when the CFR value after nightshift work returns to baseline level. Fourth, there is a high interindividual variability in tolerance to shift work. Although sleep and mental disorders are considered the main adverse effects of shift work on overall health status, other confounding factors may influence the outcome.