Sleep Duration is Closely Associated with Suicidal Ideation and Suicide Attempt in Korean Adults: A Nationwide Cross-sectional Study

Abstract

Introduction: Suicidal ideation and suicide attempts are major risk factors for suicidal death, and sleep problems are associated with an increased risk for mental disorders. We investigated the relationship between sleep duration and suicidal ideation and suicide attempts in a representative sample of the Korean general population from a nationwide survey.

Methods: We analyzed data collected from the Korea National Health and Nutrition Examination Survey VI and VII (2013–2018). Suicidal ideation was identified via self-report and we accessed suicide attempt history. Sleep duration was divided into three categories: short sleep duration (SSD) (≤5 h), normal sleep duration (NSD) (>5 and <9 h), and long sleep duration (LSD) (≥9 h). Sampling weights were applied to obtain estimates for the general Korean population.

Results: Overall, 4015 (12.0%), 25,609 (76.5%), and 3857 (11.5%) participants were in the SSD, NSD, and LSD groups, respectively. Among these groups, 7.2%, 2.8%, and 3.3% reported suicidal ideation, 1.2%, 0.4%, and 0.7% reported a history of suicide attempts. Multiple regression analyses revealed that SSD was significantly more strongly associated with suicidal ideation (adjusted odds ratio [AOR] 1.46, p < 0.001) and attempts (AOR 2.05, p = 0.003) than NSD. No association was found between LSD and suicidal ideation/attempts.

Conclusion: Sleep duration is significantly associated with suicidal behavior, and SSD was particularly closely related with an increased risk for suicidal ideation and suicide attempt. Clinicians should carefully consider sleep duration in suicidal patients.

Introduction

Suicide is a major health problem worldwide, with nearly one million deaths to suicide per year ¹. In Korea, the suicide rate was 29.1 per 100,000 people in 2013, ranking first among developed countries, and was the fourth cause of death after cancer, cardiovascular disease, and cerebrovascular disease ². Suicidal ideation and suicide attempts are some of the strongest risk factors for suicidal death, and can result in injuries and hospitalizations that represent a financial societal burden of billions of dollars ³. Therefore, investigating the risk factors for suicidal ideation and attempts is considered an important element of formulating suicide prevention strategies.

Sociocultural, environmental, psychological, and biological factors contribute to suicidal ideation and suicide attempts ^4–6. Recently, sleep disorders such as insomnia and excessive sleep have been reported to be risk factors for suicidal ideation and suicide attempts ⁷. Sleep is essential for health and well-being, including cognitive abilities, physiological processes, emotional regulation, physical development, and quality of life ⁸. Sleep is also known to be closely related to depression and mental disorders such as bipolar disorder and anxiety disorder ⁹. Previous studies have reported that a short sleep duration is associated with a heightened suicide risk ^{7, 10, 11}. However, whether sleep duration and suicidality exist independently of other mental disorders is unclear, and the direct mechanisms underlying a potential causal relationship between sleep time and suicide have not been identified ¹².

Although multiple factors such as socioeconomic environment and mental health problems are associated with suicide, few studies have investigated the relationship between sleep duration and suicidal ideation after correcting for depression, health status, and sociodemographic factors in the general adult population in Asia ^{13, 14}. One previous study that did correct for these factors found an association between sleep duration and suicidal ideation in Korean adults ¹¹. However, that study did not consider suicide attempts, which, along with suicidal ideation, are a major risk factor for suicide.

To address this, we conducted a cross-sectional study using a large-scale sample representing Korean adults. We corrected for potential confounders such as depressive mood, health status, and sociodemographic factors to comprehensively evaluate the association between sleep duration and suicidal ideation and suicide attempts.

Materials And Methods

Results

A total of 42,217 people participated in the KNHANES examination and health survey during the study period. Excluding those under the age of 18 (10,110 people) and those who did not complete the sleep duration survey (3626 people), data from 33,481 people were included in the analyses (Fig. 1). 

Discussion

In this nationwide cross-sectional study based on a representative sample of the general population in Korea, we investigated the association between sleep duration and suicidal ideation and suicide attempts. We found that SSD (≤ 5 h) is an independent risk factor for suicidal ideation and suicide attempts.

When faced with suicidal patients, clinicians tend to focus on identifying events or stressors that may have triggered suicidal behaviors and treating any mood symptoms such as depression or anxiety. However, our data indicate that sleep duration, particularly SSD, is one of the strongest risk factors for suicide attempts, as well as suicidal ideation. This finding is consistent with previous studies, which have shown a U-shaped relationship between sleep duration and suicidal risk ^{10, 11, 18}, where suicidal risk is higher in short sleepers. In addition, a recent study reported that LSD is related to suicidal ideation and that SSD is related to suicidal behaviors in general ¹⁹. Therefore, clinicians should be aware that sleep duration is closely related with suicidality and thus carefully monitor sleep duration when treating suicidal patients.

Sleeping for a normal duration is necessary to regulate body functions and resources that are depleted during the day and plays an important role in the functional recovery of the central nervous system, which is essential for maintaining overall health ¹⁵. However, insufficient sleep can lead to various psychological and physiological disorders, including impaired judgment, decreased concentration, and poor impulse control, along with endocrine and immunological changes ^{20, 21}. Although the exact mechanism of the association between sleep disturbance and suicidal tendencies has not been clearly elucidated, it may be related to the inhibition of 5-hydroxytriptamine ^{22, 23}. In addition, inflammation markers, particularly interleukin-6, may be associated with suicidal risk in patients with sleep disorders ¹⁹. As we did not explore the mechanisms linking sleep and suicide risk in the present study, additional clinical trials are needed.

Low socioeconomic status, vulnerable health status, disability, and depression are well-known risk factors for suicide, and other factors such as marital status and family history have also been reported ^{24, 25}. An epidemiological survey of mental health conditions which was conducted nationwide in Korea indicated that mental disorders, alcohol consumption, and smoking were related to suicidal behaviors ²⁶. In this study, we adjusted not only for socioeconomic factors, marital status, health behavior, and health status, but also for depressive symptoms. We found that the odds ratio of suicidal ideation and suicide attempts in the SSD group gradually decreased as we increased the number of adjustments. This suggests that suicidal risk can be mediated by these factors.

The major strength of this study is the large, population-based dataset, which enabled us to evaluate the relationship between sleep duration and suicidal ideation and suicide attempts in the general population. Our results are consistent with those of previous studies on the relationship between sleep duration and suicidality conducted in Korea and China ^{10, 11}. Therefore, our findings can potentially be generalized not only to the Korean population but also to general Asian populations. To the best of our knowledge, this is the largest study to examine the association between sleep duration and suicidal ideation and suicide attempts in an Asian population.

However, some limitations must be considered. First, this study had a cross-sectional design and used data from a national health survey. Therefore, we were only able to evaluate simple correlations, and thus did not examine the causal relationship between sleep quantity and suicidal ideation and suicide attempts. Second, the relationship between sleep duration and suicide may vary depending on ethnicity and race. Because the KNHANES survey is based on the general population of Korea, care should be taken when applying findings from this dataset to other population groups. Third, we were unable to evaluate the mechanisms underlying the relationship between sleep and suicide risk. Therefore, a future well-designed large-scale study is needed to overcome these limitations.

Conclusion

Sleep duration was strongly associated with suicidal ideation and suicide attempts. Specifically, suicidal ideation and suicide attempts were significantly more frequent in people who had fewer hours of sleep, and short sleep duration was particularly strongly associated with suicide attempts. As such, sleep duration can be considered an independent and strong risk factor for suicidality, with important clinical implications for patients with suicidal ideation and who attempt suicide.

Declarations

Author’s contributions

SH designed the study. SH and JEM performed the analysis and YK wrote the manuscript. YK contributed to the interpretation of the results. SH conduct of the cross-sectional study as well as in critical reviewing of the manuscript. All authors approved the final version.

Conflicts of interest

The authors declared no potential conflicts of interest with respect to the research, authorship and/or publication of this article.

Consent for publication

Not applicable.

Acknowledgments

This work was supported by the Soonchunhyang University Research Fund.

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