Sudden and unexplained death in sleep (SUDS) is a leading cause of death of young men in several Asian populations. The immediate cause is ventricular fibrillation in the absence of known disease. A strong environmental component may be inferred from the regional nature of SUDS in groups that are culturally and genetically distinct and the rapid decline in rates of SUDS after migration of Southeast (SE) Asian refugees to the United States. Risk of SUDS rises sharply to a peak among men aged 35 years of age, then declines with increasing age. In a pilot studies of SE Asian refugee men in Thailand with the highest known risk of SUDS, the investigators documented high-prevalences of prolonged heart rate corrected QT interval (QTc), thiamine deficiency, hypokalemia, and a positive association between poor thiamine status, measured by erythrocyte transketolase activity (ETK), and QTc. These limited studies were unable to precisely quantify the relationship between QTc and thiamine status, lacked sufficient power to examine the relationship between QTc and hypokalemia, did not include other electrolytes, and did not address the striking differences in risk of SUDS by sex and age.