Oral health in early- and mid-adulthood is essential for the improvement of one's QOL, this study was investigated to include an epidemiological analysis of the relationship between tooth loss and life style, such as smoking, regular exercise, and the food habits of approximately 2,000 employees. Compared with the group with mild or no periodontal disease (CPI of 0, 1, or 2), the frequency of tooth loss in the group with advanced periodontal disease (CPI of 4) was 2.00 times (odds ratio, 2.00; 95% confidence limit, 1.37 to 2.93). The probability of tooth loss showed statistical significance in relation to smoking, alcohol drinking, and frequency of meals. Compared with non-smokers, the probability that current smokers will lose teeth is 1.53 times greater (odds ratio, 1.53; 95% confidence limit, 1.20 to 1.96). It was concluded that periodontal disease and smoking must be averted for preventing tooth loss.