Suicide is a serious public health burden worldwide, with nearly 800,000 deaths from suicide in 2016.1 An estimated 24.6 persons per 100,000 died from suicide in 2016 in Korea, which has had a top suicide rate among the Organization for Economic Co-operation and Development countries since 2003.2 Suicide rates increase with age, especially in Korea, and suicide rates among the elderly are almost 13-fold higher than those of teenagers.3 Though the suicide rate among the elderly has been decreasing, it remains high, at 48.6 persons per 100,000 in 2018.4

The elderly are likely to plan and choose highly lethal suicide methods rather than attempting suicide impulsively, thereby leading to higher suicide success rates.56 Among the elderly, more complex factors are known to contribute to suicide, which is in contrast to younger individuals, where a single dominant factor is often the root cause.7 Mental illness such as depression, as well as physical illness due to chronic disease, and low socioeconomic status are independent risk factors for suicide attempts.8910 Social isolation and functional disability due to aging are known to interact with other factors and increase suicidal ideation and attempts.111213

According the National Emergency Department Information System data in 2017, which is a nationwide emergency department (ED)-based database in Korea, self-poisoning was the most common method among those who attempted suicide. The proportion of choosing self-poisoning as a suicide attempt increased with age, from 2.9% among those aged < 9 years, to 76.7% among individuals in their 80s.14 One study conducted in Korea reported that among drug-related suicide attempts, the elderly used hypnotics more frequently, and had a higher admission rate and required longer hospital stays.15 Because the ED is the first place where medical intervention takes place after suicide attempts, it is important to provide adequate medical assistance in the ED to those who attempted suicide.16 Korea has been providing an ED-based case management program for people who attempt suicide since 2013. Though it has the advantage of providing psychosocial treatment and rehabilitation programs to these patients, it has only reported limited clinical outcomes so far.1718

To our knowledge, there is no nationwide research on the clinical characteristics of elderly patients who attempted poisoning by suicide in Korea. The purpose of this study was to evaluate the characteristics of elderly patients who attempted suicide by poisoning, and to identify risk factors affecting suicide attempts.

A total of 44,480 patients visited the ED for suicide attempts during the study period. Patients younger than 19 years old and missing values for ED outcomes were excluded. Out of 40,677 adult patients, 25,904 (63.8%) attempted suicide by poisoning, of which elderly patients accounted for 19.9% thereof (5,164) (Fig. 1).

Elderly patients were more likely to be male and unemployed with an education level below high school, and use EMS (all P < 0.001). Less alcohol consumption at the time of ED visit and, no prior suicide history were observed in the elderly compared to younger patients (45.9% vs. 25.4% for alcohol consumption, and 55.1% vs. 66.6% for no previous suicide attempts, respectively, all P < 0.001). Among the type of self-poisoned substances, psychiatric drugs (43.4%) were the most common, but elderly patients more used pesticides (50.3%). The most common suicide motive among all patients was an interpersonal problem (32.2%) but, a large proportion of elderly patients attempted suicide due to poor physical health (26.7%). The interval from injury to ED arrival, and ED length of stay were longer, and admission rates to hospital and intensive care units (ICU) were higher among the elderly (all P < 0.001). Elderly patients showed greater mortality than the younger group (13.8% vs. 2.9%, P < 0.001) (Table 1).

Though the mortality rate of patients who attempted suicide in both groups decreased across the study period, the mortality rate of the elderly patients was 6-fold higher than that of the younger group (Fig. 2). Fig. 3 shows the trends in the type of self-administered poison on a 10-year age band. The proportion of psychiatric drugs was high across all age groups and pesticides were the most common substance for self-poisoning among those aged > 60 years. Fig. 4 shows the differences in mortality rates by self-administered poison between the two groups. It was found that 79.5% of the elderly patients died from pesticide poisoning, while in the non-elderly group, 59.1% died from pesticide, and 24.4% died of gas-poisoning.

Factors that were identified as independent risk factors among elderly patients who attempted suicide were: male sex, unemployed status, an education level of high school or less, being injured during the day-time, having national health insurance, no alcohol consumption, the use of pesticides in the suicide attempts, poor medical health as a suicide intention, and no prior suicide attempt history (Table 2).

Suicide among the elderly is an important public health concern as life expectancy is increasing rapidly and suicide rates increase with age. According to Korean statistics, hanging is the most common suicide method, affecting 12.7 persons per 100,000 (52.3%), but among those who attempted suicide and subsequently visited the ED, self-poisoning was the predominant suicide method.14 Therefore, it is necessary to identify the characteristics of elderly patients who attempt poisoning and classify the substances ingested. In our study, elderly patients who attempted suicide by poisoning were more likely to be admitted to a hospital and ICU, and the average ED length of stay was longer and total mortality higher than in younger patients. All these poor outcomes were consistent with previous studies, which implied more distinct suicide intent or lower physical resilience among the elderly.152021

There are some variations in the frequency of self-administered poisons. Two studies conducted in Australia reported that benzodiazepine was the most commonly ingested drug for poisoning by elderly patients.2122 Other studies conducted in a single medical center in Korea showed that the most commonly ingested drugs among elderly patients were hypnotics (59.1%) and psychotropics (54.6%), respectively.1520 However, when expanding the scope of the self-administered poison to drugs, a 5-year observational study in Korea reported that the most common self-administered substance was pesticides in male patients and sedative-hypnotics in female patients.23 Our results also showed that the proportion of those who self-administered pesticides increased with age, and accordingly, the mortality rate in the elderly was higher than in the younger patients.

Risk factors associated with elderly patients who attempted suicide through poisoning were similar in previous reports.91012 Being male, with a low socioeconomic status (such as being unemployed) and education level, and poor physical health as a suicide intention were independent risk factors for suicide attempts by poisoning among the elderly, which were consistent with previous studies. Poor physical health, caused by multiple comorbidities as well as frailty due to aging, may exacerbate the lethality of suicide attempts and therefore, is known to be a unique risk factor for suicide among the elderly. Various types of stressors such as the death of a spouse, family discord, loneliness, and poor social support, were difficult to evaluate from our results, and may contribute to suicidal ideation and attempts among the elderly.24 Elderly patients who attempted suicide by poisoning showed specific characteristics at the ED visit: lower alcohol consumption, a history of fewer prior suicide attempts and fewer treatments for psychiatric illnesses, with diagnosed mental disorder such as depression. These factors were related to the fact that elderly patients tended to plan suicide attempts rather than being impulsive, and used pesticides to ensure a higher success rate.15202122 By identifying those risk factors, we should be able to identify the elderly who are at high risk for suicide, and apply proper strategies for suicide prevention.

Pesticides are well known to be fatal substances that are directly linked to death. In Korea, paraquat has been prohibited since 2011, and several studies have reported a decrease in suicide rates using this method since then.2526 However, strong regulation and control of pesticides should be maintained as the suicide rate through pesticide poisoning is still high among the elderly.27 Similarly, in Korea, there is an effort to establish a poisoning information database to provide emergency treatment information for patients presenting to the ED with poisoning.28 Community-based suicide prevention programs are also effective for enhancing physical health, reducing stress, and decreasing depressive symptoms. It can identify the elderly at high risk for suicide, and provide additional timely interventions.2930 Case management provides those who attempt suicide with psychosocial treatment from ED admission, and links them to the appropriate community services. Although the clinical effect of case management on suicide prevention has been reported to be controversial,31 recent studies conducted in Korea reported its effectiveness for reducing the risk of suicide.1718

This study has several limitations. First, this is a retrospective observational study and may have potential confounders that influenced the exposure and outcomes. Second, there are quite a few missing values for some variables, such as occupation or education level because they are defined as mandatory variables only at admission. Finally, since the EDIIS database used in this study comprises mainly injury-related information, and certain psychosocial variables such as psychiatric disorders (especially like depression), current psychiatric medication, marital status, and cohabitant status, which are known to be important risk factors for suicide attempts in the elderly, were not available; therefore, it is difficult to generalize the results of our study.

In conclusion, attempted suicide by poisoning among the elderly is associated with poor clinical outcomes compared to that among younger patients. Male sex, low socioeconomic status, poor physical health, pesticide use, lower alcohol consumption, and a history of fewer prior suicide attempts were found to be risk factors for suicide among the elderly. Suicide among the elderly is a potentially preventable public health problem, where further multidisciplinary interventions are needed.