Suicide has long been recognized as a major public health and economic problem in various cultures [1,2]. In 2002, an estimated 877,000 lives were lost worldwide through suicide, representing 1.5% of the total global burden of disease and more than 20 million disability-adjusted life-years (years of healthy life lost through premature death or disability) [3]. In contrast to the overall decrease in suicides among most industrialized countries over the last decade, Korea have experienced an increase in suicides. Between 1995 and 2006, Korea recorded the highest degree of suicide increase among the Organization for Economic Cooperation and Development countries, from 11.2 deaths per 100,000 to 21.5 [4]. Korea currently ranks first in the world, with a suicide rate of 33.4 for men and 18.7 for women in 2008 [4].

Sudden cardiac arrest (SCA) is normally the final process of successful suicides. Suicide-associated SCA (S-SCA) is most likely to be treated at the scene by emergency medical service (EMS) providers, transported by EMS, and subsequently managed by emergency department (ED) physicians as SCAs with a cardiac etiology. S-SCAs can provide valuable information on many different factors surrounding suicide attempts, such as the attempt method, time-course of the attempt, geospatial characteristics, presence or absence of witnesses, bystanders and bystander activity, EMS response time and services, and treatments initiated at the hospital. Previous studies described this information in S-SCAs caused by drowning, poisoning, and hanging [5-7].

This study aimed to describe the epidemiologic characteristics of SCA associated with suicide attempts and to investigate outcomes after S-SCA stratified by the different suicide attempt methods.

The study was approved by the Institutional Board of Review at the study institution and financially supported by the Korea Centers for Disease Control and Prevention (2008 to 2011).

Mechanisms for suicidal attempt are various, differ according to cultural background, and may change over time [2]. People who have suicidal ideations generally seek isolated areas to avoid bystanders, use fast-acting suicide methods to reduce fear and pain, and ensure success via methods with a high rate of lethality [13-15].

Suicide attempt patients are typically found in three different types of clinical situations: aborted suicide attempt, SCA, or death due to prolonged cardiac arrest (PCA). Aborted suicide is an incomplete suicide, while SCA and PCA are complete. Due to social, cultural, or religious backgrounds that regard suicide as a crime, conflicts within families, psychiatric disorders, and confidentiality, data on aborted suicides are extremely difficult to collect and analyze [16]. Patients who experience PCA secondary to suicide are directly transported to the mortuary. The death certificates in these cases have limited information, making it difficult to adequately interpret the environment and characteristics of the suicide [17].

This study is important for several reasons. An S-SCA database may be a good resource to understand various characteristics of suicide and to develop suicide prevention programs. Patients with S-SCA possess a host of information from the scene, which is a source of insight into primary prevention, EMS services, and hospital care and support for secondary prevention of suicide. Nationwide or community-based SCA registries, in particular OHCA registries, have been developed in both Asian and Western communities [18]. Most SCA research focuses on SCA with presumed cardiac etiology or trauma-associated SCA rather than S-SCA. In Korea, which has a higher incidence of suicide, an S-SCA registry could prove to be a key resource in understanding the suicidal environment and method of choice; these data in turn may help to prevent suicide and improve resuscitation efforts and outcomes.

Suicide-associated SCA was observed to occur most commonly from hanging (58%) and was responsible for 13.4% of the total mortality rate from suicide of 32.1 per 100,000 persons, or 4.3 deaths per 100,000 persons. The survival to discharge rate was extremely low in all mechanisms of suicide and found to be even lower in falls compared with other methods of suicide in our nationwide S-SCA patients.

Our findings also demonstrated epidemiologic and geographic variability stratified by potential risk factors according to the different mechanisms of suicide. For example, non-metropolitan areas showed a relatively higher use of poisoning as a method of suicide rather than falls or hangings. This is in contrast to a separate study that demonstrated higher proportions of hanging in urban (18.0%) compared to rural environments (14.9%) [19]. In another population-based study from metropolitan Melbourne, Australia, hanging for suicide was common in the younger (median age 39 years) and male group (88%) [20]. In another study from Taiwan, poisoning was found in higher rates in rural areas (32.1%) than in urban environments (30.5%) [21]. Our study showed hanging and poisoning was 57.7% and 73.5% in non-metropolitan areas, respectively. Poisoning has been a common method to attempt suicide in rural areas; however, our SCA registry showed much higher proportions of poisoning in rural areas than previously reported.

Our study suggests that different age groups tend to select different methods of attempting suicide. The young adult population (15 to 65 years) preferred hanging (62.6%) over poisoning (12.1%) or falls (18.6%), whereas elderly people selected hanging (34.3%). More than half of the pediatric patients (<15 years) selected falls (56.9%) as the preferred method of suicide. One study showed much higher proportion of hanging (53.1%) in young adult compared with poisoning (34.1%) or falls (12.8%) [22]. In another study from Hong Kong, carbon oxide from charcoal burning was an emerging method to commit suicide [23]. Charcoal burning constituted 18.3% of all suicides in the study. Additionally, 88% of those that used charcoal burning were from the middle years (25 to 59) of life. The mechanism used to attempt or commit suicide has very strong sociocultural background and may change over time.

We found very interesting findings when analyzing monthly trends in this study. October 2008 showed a peak of hangings, which continued to the end of the observational period. We searched social events in this period and found two consecutive celebrity suicides on September 8 and October 2, 2008. In particular, the latter celebrity was a popular actress starring on a television drama in Korea. Major television news, newspaper reports, and internet media reports continued to report the event and method daily for a month. The first had attempted suicide via gas poisoning from charcoal burning, and the second used the hanging method. We believe the peak in October was due to copycat suicides and Werther’s effect [24], as has been reported in many communities [25,26].

We found very low rates of survival to discharge and neurological recovery in this study. Most previous studies reported outcomes on SCA with cardiac etiologies or trauma. From our previous reports, survival to discharge rates of SCA with presumed cardiac etiology transported by EMS was 3.7% in 2008 [27]. Other reports on survival to discharge rates of SCA with an etiology of trauma was 1.0% [28]. Hanging-associated SCA showed a very low survival to discharge rate (0.5%) in another study with a small sample size [20]. Our study demonstrated that lower survival to discharge rates in S-SCA is associated with lower witness rates (10.0%), a private place (81.9%), lower bystander CPR rate (2.6%), asystolic rhythm (81.6%), and more serious methods of suicide such as falls (17.6%). Being in an isolated, private place for a suicide attempt is the main cause of extremely low witness rates and bystander CPR rates. This in turn leads to a high proportion of patients found by EMS to be in asystole and unable to be resuscitated. Our strategy for improving outcomes is to increase bystander CPR, even if the patient’s suicide attempt is not witnessed and the patient is found at the scene after S-SCA. To improve bystander activity, we can encourage more specific population programs, such as dispatcher-assisted bystander CPR [29]. However, more specific strategies for preventing suicide as well as improving bystander activity should be considered to remove the environmental conditions that favor suicide and to enable earlier detection in people at high risk of attempting suicide.

EMS-assessed and S-SCA registries can be extracted daily, as many communities have automated and electronic database systems in place. These registries will be very helpful for preventive strategies, because they allow for surveys and for the formation of daily and monthly suicide event trends. They may therefore assist in finding persons and locations at high risk of a suicide.

This study used a retrospective medical record review for measuring outcomes and risk factors. Additionally, there were many missing cases in some important variable categories. There were 1,539 cases without information on intentionality of the patient’s suicide attempt. Although many observational studies on suicide have huge proportion of unknown intentionality, this unknown group can cause bias and underestimate the incidence rate by specific method. This study was performed in an EMS system with intermediate service level, which is a relatively lower level compared with those of North America and Europe [9]. Therefore, our results may not be generalized to those communities. This study included cases in SCA status at the time when bystander witnessed or found the patients. If we added more cases of aborted suicide attempts or PCAs not requiring an ambulance transport, our results may be significantly changed.

In conclusion, from an EMS-assessed suicide-associated SCA registry, we found a suicide rate of 39.4 per million persons and a 2.1% rate of survival to discharge. Suicide by falls was associated with a significantly lower chance of survival to discharge as compared with suicide by hanging.