To prevent "life style-related diseases", it is necessary to evaluate not only the factors directly related to sleep but also the relationship between sleep and other life style-related factors (such as smoking, alcohol drinking, food habits, and exercise routines). There have been no extensive studies conducted on these relationships. A survey was conducted on 2,000 employees of a large plant over a 6-year period to provide data that would allow one to analyze correlation between hours of sleep and other life style factors, such as smoking, alcohol drinking, dietary habit, and exercise. It focused on a serial evaluation, with special reference to the correlation between sleep and smoking and drinking habits, exercise, and food habits. In relation to smoking or an alcohol drinking habit, no significant correlation was found between those who did not get enough sleep and those who got adequate sleep. For the dietary habits, the group with insufficient hours of sleep was related to a less than satisfactory frequency of meal taking, irregularity of eating, snacking habits, excessive seasoning of food, and consumption of insufficient quantities of vegetables. Conversely, it was recognized that those who have satisfactory food habits are more likely to enjoy an appropriate amount of sleep. Those who fail to get sufficient sleep engage in food habits that are more likely to cause life style-related diseases.