By 1981–1982, the annual rate in the United States was high with 92/100,000 among Laotians-Hmong, 82/100,000 among other Laotian ethnic groups, and 59/100,000 among Cambodians.In a 2008 study it was found that over half of SADS deaths could be attributed to inherited heart disease: unexplained premature sudden deaths in family, long QT syndrome, Brugada syndrome, arrhythmogenic right ventricular cardiomyopathy and others.A national SADS study in England, funded by the British Heart Foundation, reported results in a 2007 journal article published in Health. The study surveyed 117 coroners jurisdictions in England. Researchers found that deaths from SADS reported by these coroners occurred "predominantly in young males". There were 500 cases a year in England, which is 8 times more than was previously estimated. Families are more at risk of SADS if they have a genetic cardiac disease. The study recommended that affected families should undergo "specialised cardiological evaluation". Asia
Southeast Asian immigrants, who were mostly fleeing the Vietnam War, most often had this syndrome, marking Southeast Asia as the area containing the most people with this fatal syndrome. There are other Asian populations that were affected, such as Filipinos and Chinese Filipinos, Japanese in Japan, and natives of Guam in the United States and Guam. The immigrants with  this syndrome were about 33 years old and seemingly healthy, and all but one of the Laotian Hmong refugees were men. The condition appears to primarily affect young Hmong men from Laos (median age 33) and Northeastern Thailand (where the population is mainly of Laotian descent).
Although there is no real known definite cause, extensive research showed people 18 years or older were found to have had a hypertrophic cardiomyopathy, a condition in which the heart muscle becomes oddly thickened without any obvious cause. This was the most commonly identified abnormality in sudden death of young adults. In the instances where people experience sudden death, it is most commonly found that they had had CAD (coronary artery disease) or ASCAD (atherosclerotic coronary artery disease), or any level of stress. However, studies reveal that people experienced early symptoms within the week before the terminal event such as chest pain at ~52% of patients, dyspnea at ~22%, syncope at ~7% and ~19% who experienced no symptoms. Scientists have also associated this syndrome with the gene SCN5A that is mutated and affects the function of the heart. However, all autopsies done on those who had this syndrome came back negative.In the Philippines, bangungot (or in their term, sudden adult death syndrome) is mainly caused by the Brugada syndrome. Diagnosis
Diagnosis occurs post-mortem. Treatment
The only proven way to prevent SADS is with an implantable cardioverter-defibrillator. Oral beta-blockers such as propranolol are ineffective. Epidemiology
In 1980, a reported pattern of sudden deaths was brought to the attention of the Centers for Disease Control. The first reported sudden death occurred in 1948 when there were 81 similar deaths of Filipino men in Oahu County, Hawaii. However, it did not become relevant because there was no associated pattern. This syndrome continued to become more significant as years went on.