One of the strengths of a biocultural perspective in anthropology is its broad approach to understanding human biology and health (Wiley and Allen 2008). Such a framework seems particularly appropriate when looking at the fascinating phenomenon of SUDS (Sudden Unexplained Death During Sleep). Though SUDS first appeared in the medical literature 1917 in the Philippines, where it is referred to as ‘bangungut’ (Guazon 1917), it was largely forgotten until the late 1970s when it regained notoriety as an important cause of mortality among Southeast Asian refugees in the United States, particularly among young men (Baron et al 1983).
Unlike the similar-sounding condition of SIDS (Sudden Infant Death Syndrome), SUDS has a completely different and more mysterious epidemiology and etiology. Although both conditions are sleep-related, the vast majority of SUDS cases are males (75-100% in various studies), young adults (average age of 30-34), with no previous history of health problems (Munger 1987). In addition, it appears to be largely concentrated among, if not exclusive to, persons of East and Southeast Asian origin. Family members who witnessed a SUDS case reported that victims had difficulty breathing, made groaning sounds, and were generally unresponsive. In short, it’s pretty bizarre. To solve the puzzle of SUDS, one needs to account for all of these factors (Asian, male, young adult, previously healthy, and during sleep).
At first, there was a tendency to view SUDS as a culture-bound syndrome, limited to persons of Hmong ethnicity. A new term, ‘Hmong Death Syndrome,’ was coined to describe the mysterious illness (Bliatout 1982; New Scientist 1982) before recognizing that other ethnic groups residing in both western and Asian countries were similarly afflicted, such as the Khmer, Lao, Khmu, Thai, Vietnamese, Filipinos, Japanese, and Guamanian Chamorros (Munger and Booton 1998; Tatsanavivat et al 1992). The focus on the Hmong was likely due to an American view of them as exotic newcomers from the highlands of Laos, but was also fed by Hmong animistic spiritual beliefs of the phenomenon (Fadiman 1998). Many persons of Hmong ethnicity have described being personally attacked and held down by a malevolent spirit during sleep (tsog tsuam), leaving them conscious but paralyzed (Adler 1995). Obviously, these attacks were not fatal.
What is interesting is that such experiences are found in many cultures, not just the Hmong. Al Cheyne at the University of Waterloo in Ontario has documented that the concept of being crushed by a ghost at night exists throughout the world (even the English word ‘nightmare’ may trace its origins to this), and that this may be related to a condition called sleep paralysis. In effect, sleep paralysis occurs when someone experiences a disconnect between waking and REM sleep (when muscle activity is suppressed), leaving a person conscious but unable to move voluntarily. However, while sleep paralysis appears to fit the nocturnal pattern of SUDS and the common cultural view of a being paralyzed by a ghost, it remains unclear why some of these cases would be fatal.
The immediate or proximate cause of death in SUDS has been determined to be ventricular fibrillation- a rapid, ineffective beating of the ventricles of the heart. By chance, three cases of SUDS attacks endured long enough to allow medical personnel to examine the victims while still alive, all of whom exhibited ventricular fibrillation (Otto et al 1984).
If ventricular fibrillation is the proximate cause of SUDS, the ultimate cause remains elusive. Hypotheses have ranged from genetics to infection to nutritional deficiencies to culture shock in newly adjusting refugees (Wong et al 1992). The notion of culture shock or psychological stress (while intriguing) never gained much traction, as it could not address important components of SUDS epidemiology, including why males were disproportionately affected, why individuals succumbed during sleep, and why refugees from regions other than Southeast Asia were not affected.
A genetic predisposition seems a necessary component for SUDS in order to account for its concentration in males from Asian populations, though it appears insufficient by itself. Instead, a complex interaction between genes and environmental factors may be in play. For the cases in the U.S., most fatalities occurred in refugees who had recently arrived (median length of time in the country was 4 years), with risk decreasing with time (CDC 1988). Furthermore, death rates from SUDS in the late 1980s were actually higher in refugee camps in Thailand than in the U.S. (Munger and Booton 1990), which was yet another strike against the culture shock hypothesis. In fact, while research continues in Asia, cases appear to have leveled off in the U.S. almost completely (or at least have not received much attention).
The biology of SUDS appears complex. Genetic studies have inquired whether there is a link between SUDS and cardiac sodium channel gene (SCN5A) mutations (Sangwatanaroj et al 2002), and whether it is linked to Brugada Syndrome, a fairly newly recognized condition with a similar electrocardiographic (ECG) profile and is also concentrated more in males (Brugada et al 1999). Brugada Syndrome has been described as being an autosomal dominant genetic condition, with a mutation traced to chromosome #3.
However, if SUDS and Brugada are in fact the same condition, some questions still remain. For one, why is sleep such an important factor in SUDS? (Brugada is not described as sleep-dependent.) Why are males vastly more likely to be affected if the condition has a simple autosomal inheritance? Is the suspected allele more common in Asian populations?
Most importantly, are there environmental variables that increase the risk for SUDS? Munger et al (1991) reported that ECG tests revealed that a prolonged QT heart interval (a specific measure of the heart’s electrical cycle) was found in 12% of the Thai camp refugees, 1.3% of Southeast Asian refugees in the U.S., and 0.5% of U.S. Blacks and Whites. QT intervals are normally lengthened during sleep, but an excessively prolonged interval may induce heart arrhythmias, including ventricular fibrillation. Munger and Booton (1990) suspected that a deficiency in thiamin (vitamin B-1) could lead to prolonged QT intervals. Perhaps substandard diets in refugee camps could help trigger the condition, partly explaining why rates were higher there and why rates have declined in the U.S. over time.
There is still much to be worked out regarding SUDS, given its complex epidemiology and biology. Anecdotally, I know Hmong individuals who described experiencing tsog tsuam/ sleep paralysis in the recent past, in both the U.S. and French Guiana. Fortunately, the fatalities have dropped considerably in the U.S., though they appear to remain steady in Asia. The mystery continues.
The above photo shows Hmong men in Huay Nam Khao refugee camp, praying for a peaceful life. From the Bangkok Post.
Adler SR. 1995. Refugee stress and folk belief: Hmong sudden deaths. Social Science and Medicine. 40 (12): 1623-9. Link
Bliatout, Bruce Towpaou. 1982. Hmong Sudden Unexpected Nocturnal Death Syndrome: a Cultural Study. Portland, Oregon: Sparkle Publishing Enterprises, Inc. Link (full ref)
Baron RC, Thacker SB, Gorelkin L, Vernon AA, Taylor WR, Choi K. 1983. Sudden death among Southeast Asian refugees. An unexplained nocturnal phenomenon. JAMA.250(21):2947-51. Link
Brugada J Brugada P Brugada R. 1999. The syndrome of right bundle branch block ST segment elevation in V1 to V3 and sudden death—the Brugada syndrome. Europace 1: 156-166. Link (full ref)
CDC. 1988. Update: Sudden Unexplained Death Syndrome among Southeast Asian refugees — United States. MMWR 37: 568-570. Link
Fadiman A. 1998. The Spirit Catches You and You Fall Down. Farrar, Giroux, & Strauss. Link
Guazon MP. 1917. Algunas notas sobre bangungut. Revista Filipina de Medicina Y Farmacia, 8: 437-42.
Munger RG. 1987. Sudden death in sleep of Laotian-Hmong refugees in Thailand: a case-controlled study. American Journal of Public Health 77(9):1187-90. Link (full ref)
Munger RG, Booton EA. 1990. Thiamine and sudden death in sleep of South-East Asian refugees (letter). The Lancet, 335 (8698): 1154-5. Link
Munger RG, Booton EA. 1998. Bangungut in Manila: sudden and unexplained death in sleep of adult Filipinos. International Journal of Epidemiology 27: 677-84. Link (full ref)
Munger RG, Prineas RJ, Crow RS, Changbumrung S, Keane V, Wangsuphachart V, Jones MP. 1991. Prolonged QT interval and risk of sudden death in South-east Asian men. The Lancet, 338 (8762): 80-1. Link
New Scientist. 1982. Independent evidence of yellow rain. Mar 11, p. 626. Link
Otto CM, Tauxe RV, Cobb LA, Greene L, Gross BW, Werner JA, Burroughs RW, Samson WE, Weaver WD, Trobaugh GB. 1984. Ventricular fibrillation causes sudden death in Southeast Asian immigrants. Annals of Internal Medicine 100: 45-7. Link
Sangwatanaroj S, Yanatasneejit P, Sunsaneewitayakul B, Sitthisook S. 2002. Linkage analyses and SCN5A mutations screening in five sudden unexplained death syndrome (Lai-tai) families. Journal of the Medical Association of Thailand. 85 Suppl 1:S54-61. Link
Tatsanavivat P, Chiravatkul A, Klungboonnkrong V, Chaisiri S, Jarerntanyaruk L, Munger RG, Saowakonthra S. 1992. Sudden and unexplained deaths in sleep (Laitai) of young men in rural northeastern Thailand. International Journal of Epidemiology 21(5): 904-10. Link
Wiley AS and Allen JS. 2008. Medical Anthropology: A Biocultural Approach. Oxford University Press. Link
Wong ML, Ong CN, Tan TC, Phua KH, Goh LG et al. 1992. Sudden unexplained death syndrome. A review and update. Tropical and Geographical Medicine 44(4):S1-19. Link
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Great post, Patrick! I’ve been studying sleep paralysis cross-culturally for many years, but remain as fascinated by the topic as I was as a graduate student. My book (Sleep Paralysis: Night-mares, Nocebos, and the Mind-Body Connection) is just coming out–let me know how I can get you a copy.
Thanks, Shelley! I’ll reply via email.
I find this very interesting Patrick. Some years ago i had an experience that i can best describe’ like being held down and suffocated while i was awake, with such a strong sense of a supernatural nature to what ever was squashing me’ As bizaree as this sounds, i put this ‘nightmare’ down to the house i was in being haunted and left it.
However now 20 years later i have recently been diagnosed with type 1 Brugada syndrome and now feel there might be more to the experience than i realised at the time.
I am of Dutch heritage
Hi Mr. Clarkin, I’m a medical doctor here in the Philippines and I don’t have the exact statistics of “sudden death” among males in my country, but it’s quite common and I personally know 3 young men who have suddenly died without any background medical condition. I’ve encountered some of the beliefs during my undergrad in one of my anthropology classes but they were mostly superstitions and not the exact explanation of their condition.
There are many theories about it…from acute pancreatitis to pulmonary thrombosis. But during med school, our doctors believe that it may be a hypertrophic cardiomyopathy, common among young adult (usually athletic) men. This usually can cause fatal arrhythmias, and it can strike any time of the day, like the brother of my friend who suddenly collapsed while in class and didn’t recover.
Thank you for the post…it’s an interesting perspective seeing a medical condition in a cultural perspective.
How does one get tested and diagnosed? My husband has lost both his brothers to this I believe – one aged 31 (coroner hinted to this disease) and the other 36 yesterday who is yet to be autopsies. He is 1 of 8 children 4 girls and 4 boys there are only 2 boys left. He is of Vietnamese heritage and fled as a refugee from Vietnam 30+ years ago
I’ll reply via email.
Great piece. We discussed this in my AP Psych class after a student brought up SUDS while we were discussing sleep disorders. I was not familiar with it so I did a little digging and came upon this. Thanks.
Hi Dr, Clarkin. I am a genetic counseling student from the Philippines. Your article was very enlightening considering that many cases of bangungut have been documented in the country since the publication of Dr. Guanzon’s article in early 1900s. I am particularly interested in Brugada syndrome and bangungut. Since this is a genetic condition, I wanted to know how the diagnosis affects the health seeking behaviors of people diagnosed with it including that of their family. I am also interested in exploring the professional and folk explanatory models of this disorder. I hope I could get in touch with you. Thanks again for this article.
Hi PJ, please contact me via email, which you can find in the “About me” tab at the top of this page.
I came i across this article while researching about brugada syndrome, My niece is suspected to have a brugada its not confirm yet until she undergo a genetic test which is unfortunately not available here in the Philippines. Anyway she is just turning 2 this Feb so they called it infantile brugada.
Hi, I am PJ Abad, a genetic counseling student from the Philippines. May I know your e-mail address? Perhaps, I could raise this up to our genetic counselor instructors from the US and the geneticists here in the Philippines. Thank you very much.
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Interesting article. My father died of SUDS in the early 1980s when we first arrived in California and my uncle apparently died of the same thing a few months later in the Thailand refugee camps. For years I never understood what happened that caused my father to died. He was young and healthy, in his early to mid 20s. It is nice to have some answers.
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