A Prospective Cohort Study of Shift Work and Risk of Ischemic Heart Disease in Japanese Male Workers

1. Yoshihisa Fujino
2. Hiroyasu Iso
3. Akiko Tamakoshi
4. Yutaka Inaba
5. Akio Koizumi
6. Tatsuhiko Kubo
7. Takesumi Yoshimur and
8. for the Japanese Collaborative Cohort Study Group

Author Affiliations

1. 
   
   
   ¹Department of Preventive Medicine and Community Health, University of Occupational and Environmental Health, Kitakyushu, Fukuoka, Japan
2. 
   
   
   ²Public Health, Department of Social and Environmental Medicine, Graduate School of Medicine, Osaka University, Osaka, Japan
3. 
   
   
   ³Department of Preventive Medicine/Biostatistics and Medical Decision Making, Field of Social Life Science, Program in Health and Community Medicine, Nagoya University Graduate School of Medicine, Nagoya, Japan
4. 
   
   
   ⁴Department of Epidemiology and Environmental Health, Juntendo University School of Medicine, Tokyo, Japan
5. 
   
   
   ⁵Department of Health and Environmental Sciences, Kyoto University Graduate School of Medicine, Kyoto, Japan
6. 
   
   
   ⁶Department of Clinical Epidemiology, University of Occupational and Environmental Health, Kitakyushu, Fukuoka, Japan
7. 
   
   
   ⁷Fukuoka Institute of Health and Environmental Sciences, Dazaifu-shi, Fukuoka, Japan

1. Correspondence to Dr. Yoshihisa Fujino, Department of Preventive Medicine and Community Health, University of Occupational and Environmental Health, 1-1, Iseigaoka, Yahata-nishi-ku, Kitakyushu 807-8555, Japan (e-mail: zenq@med.uoeh-u.ac.jp).

• Received September 5, 2005.
• Accepted February 16, 2006.

Abstract

This study prospectively examined the association between shift work and the risk of ischemic heart disease among Japanese male workers. A baseline survey, which involved 110,792 inhabitants (age range: 40–79 years) from 45 areas throughout Japan, was conducted between 1988 and 1990. The causes of death were identified from death certificates. The analysis was restricted to 17,649 men (age range: 40–59 years) who were employed at the time of the baseline survey. All subjects were asked to indicate the most regular shift work that they had undertaken previously: day work, rotating-shift work, or fixed-night work. The Cox proportional hazards model was used to estimate the risks of shift work for ischemic heart disease. During the 233,869 person-years of follow-up, a total of 1,363 deaths were recorded, 86 of which were due to ischemic heart disease. Compared with the day workers, the rotating-shift workers had a significantly higher risk of death due to ischemic heart disease (relative risk = 2.32, 95% confidence interval: 1.37, 3.95; p = 0.002), whereas fixed-night work was not associated with ischemic heart disease (relative risk = 1.23, 95% confidence interval: 0.49, 3.10; p = 0.658). In addition, subjects with coronary risk factors, such as hypertension, overweight, habitual alcohol consumption, and smoking, were highly susceptible to the effect of rotating-shift work on the risk of death due to ischemic heart disease.