Sudden unexplained death syndrome in north-east Thailand.

To study sudden unexplained death syndrome (SUDS) in north-east Thailand, a mailed screening questionnaire and direct retrospective interview of relatives or witnesses of the incident was carried out in four administrative districts of Khon Kaen Province, north-east Thailand. Healthy villagers, 20-49 years, who died suddenly without explanation were identified as cases. Live healthy villagers who were age- and sex-matched with the dead served as controls. The study showed that all but one case were male with a mean age of 38 +/- 8 years. The incidence of SUDS was 38 per 100,000 men 20-49 years old per year. The peak risk was at 45-49 years. About 75% of SUDS cases had an annual income per household of less than the mean per capita income in Thailand. There were more SUDS cases in the hot season than any other season. The onset was nocturnal in 84% of cases. Presence of SUDS in family members was more frequently found in cases than in controls (P < 0.001). A history of muscle soreness, malaise and recent hard labour were seen as frequently in SUDS victims as in controls. In witnessed cases, symptoms usually lasted for a few minutes prior to death. Common symptoms or signs were respiratory (groaning, choking or coughing) and muscular spasticity or paralysis. The most consistent but yet unexplained finding in this study is the association between the onset of SUDS and the rest period.