Lifestyle factors such as alcohol consumption, dietary habits, exercise and sleep patterns are included in the questions. Alcohol consumption is defined as type of alcoholic drink, amount per day and date when consumption began. Dietary habits include meal frequency and consumption of salts, meats, vegetables and 7 types of beverages (coffee, black tea, oolong tea, green tea, ginseng tea, fruit juice and carbonated beverage) during the past year. Exercise will be calculated according to the International Physical Activity Questionnaire (IPAQ), which is a standardized instrument for measuring the amount of exercise.9 Duration of sleep, sleep latency, frequency of waking-up after sleep onset (WASO), snoring severity, duration of naps, history of using sleeping pills and length of time in bed without sleeping will be reported to evaluate sleep patterns. Investigators will also add the validated Korean version of the Epworth Sleepiness Scale for measuring daytime sleepiness,10 and questions about restless leg syndrome.