Chronic sleep deprivation is increasingly common in industrialized societies. Short sleep duration has been associated with a number of negative health outcomes. The objectives of this study were to investigate the association between self-reported sleep duration and the presence of metabolic syndrome (combination of central obesity, triglyceride, high density lipoprotein, blood pressure, fasting plasma glucose) in adults during midlife. The Korean Genomic Rural Cohort (KGRC) is a cohort study of aged 40 to 70 years in rural Korea. This study focuses on the prevalence, incidence, and risk factors for chronic degenerative disorders, such as hypertension, diabetes, osteoporosis, respiratory diseases, and metabolic syndrome. The baseline sample of participants in the KGRC study was recruited in 2005-2006 (phase 1). Respondents were followed until 2008-2009 (phase 2). The final sample included 1,107 subjects: 386 males (34.9%) and 721 females (65.1%). The incidence rate of metabolic syndrome in our sample was 18.4% (21.2% for males and 16.9% for females). Subjects sleeping < 6 hours a day (HR: 1.798; 95% CI: 1.06-3.05) were significantly more likely to experience metabolic syndrome than participants sleeping 6 to 7.9 hours a day after controlling for potential covariates (age, body mass index, menopause, smoking, alcohol and physical activity). Shorter sleep duration was associated with the high incidence of metabolic syndrome among females only. In conclusion, shorter sleep duration may be a significant risk factor for the development of metabolic syndrome in women.