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  • Research article
  • Open Access
  • Open Peer Review

Insomnia as an independent predictor of suicide attempts: a nationwide population-based retrospective cohort study

BMC Psychiatry201818:117

https://doi.org/10.1186/s12888-018-1702-2

  • Received: 7 January 2018
  • Accepted: 23 April 2018
  • Published:
Open Peer Review reports

Abstract

Background

Numerous studies have verified that insomnia is associated with suicidal ideation, suicide attempts, and death by suicide. Limited population-based cohort studies have been conducted to examine the association. The present study aimed to analyze whether insomnia increases the risk of suicide attempts and verify the effects of insomnia on suicide risk.

Methods

This study is a cohort study using 2000–2013 hospitalization data from the National Health Insurance Research Database (NHIRD) to track the rate of suicide attempts among insomnia patients aged 15 years or older. In addition, a 1:2 pairing based on sex, age, and date of hospitalization was conducted to identify the reference cohort (patients without insomnia). Cox proportional hazard model was used to assess the effects of insomnia on suicide risk.

Results

The total number of hospitalized patients aged 15 years or older was 479,967 between 2000 and 2013 (159,989 patients with insomnia and 319,978 patients without insomnia). After adjusting for confounders, suicide risk in insomnia patients was 3.533-fold that of patients without insomnia (adjusted hazard ratio [HR] = 3.533, 95% confidence interval [CI] = 3.059–4.080, P < 0.001). Suicide risk in low-income patients was 1.434-fold (adjusted HR = 1.434, 95% CI = 1.184–1.736, P < 0.001) that of non-low-income patients. Suicide risk in patients with drug dependence and with mental disorders was 1.592-fold (adjusted HR = 1.592, 95% CI = 1.220–2.077, P < 0.001) and 4.483-fold (adjusted HR = 4.483, 95% CI = 3.934–5.109, P < 0.001) that of patients without drug dependence and without mental disorders, respectively. In the female population, suicide risk in insomnia patients was 4.186-fold (adjusted HR = 4.186, 95% CI = 3.429–5.111, P < 0.001) that of patients without insomnia. Among patients aged 25–44 years, suicide risk in insomnia patients was 5.546-fold (adjusted HR = 5.546, 95% CI = 4.236–7.262, P < 0.001) that of patients without insomnia. Furthermore, the suicide risk of insomnia patients with mental disorders was 18.322-fold that of patients without insomnia and mental disorders (P < 0.001).

Conclusion

Insomnia, low income, drug dependence, and mental disorders are independent risk factors for suicide attempts. Female patients and those aged 25–44 years are at high risk of suicide due to insomnia. Insomnia, mental disorders, and low income exhibit a synergistic effect on suicide attempts. Clinicians should pay attention to mental status and income level of insomnia patients.

Keywords

  • Insomnia
  • Suicide
  • National Health Insurance Research Database (NHIRD)

Background

Suicide is a serious public health problem around the world. The World Health Organization (WHO) reported that approximately 800,000 people worldwide die from suicide every year (an average of one death every 40 s). In addition, suicide is the second leading cause of death among those aged 15–29 years globally, and the fifth leading cause of death among those aged 30–49 years [1]. Compared with death by suicide, there are many more suicide attempts every year [2], and according to a meta-analysis from Japan in 2008, a prior suicide attempt is the most important predictor of suicide [3]. Suicide, moreover, causes immense socioeconomic burdens on families, communities, and nations [4]. In 2016, the number of deaths from suicide in Taiwan was 3765 (a suicide death rate of 16.0 persons per 100,000 population), making suicide the twelfth leading cause of death in Taiwan. The suicide death rate among men was approximately 2.1-times higher than that among women (17.0 men and 7.7 women per 100,000 population). The suicide death rate in all age groups increased with age [5].

Insomnia is one of the most prevalent sleeping disorders in the world [6]. According to epidemiological studies around the world, the prevalence of insomnia in general populations is 10%–25% [710]. A 2017 report by the Taiwan Society of Sleep Medicine indicated that a tenth of the population across Taiwan suffers from chronic insomnia (prevalence rate of 11.3%) [11]. Insomnia refers to difficulty falling asleep, remaining awake while trying to sleep, waking up often during the night, or still feeling tired after sleeping for a brief period, factors that subsequently influence daytime activities of daily living for more than four weeks. If insomnia persists for more than six months, it becomes a chronic condition influencing not only the person’s psychology and physiology but also his or her health and activities of daily living (e.g., learning and working) [12].

Numerous studies have indicated that insomnia is associated with suicidal ideation [1316], suicide attempts [1719], and death by suicide [2022] among adolescents and adults. These studies laid the foundation for the relationship between insomnia and suicide. However, there are some weakness in methodology and need future research to fill this gap. For example, some studies used a questionnaire asking a single question as criteria for determining insomnia or suicide [22]. Furthermore, mental disorders are a major confounding factor for insomnia and suicide, and over 90% of suicide decedents have at least one mental disorder [23]; however, some studies assessing the link between insomnia and suicide did not adjust for mental disorders [17, 20].

There are still different arguments about whether insomnia is an independent factor of suicide or if insomnia, as a symptom of mental disorders such as depression, increases the risk of suicide. Some studies have found that the relationship between insomnia and suicide is fully mediated by mental disorders [13, 14, 24]. Other studies have shown that insomnia remains an independent factor of suicidal ideation [15, 16], suicide attempt [19], and death by suicide [21, 22] after adjustments for mental disorders, substance abuse and alcohol abuse.

A meta-analysis by Pigeon et al. indicated that insomnia is still a predictor of suicide even after other factors have been adjusted for. However, the authors asserted that the samples collected are non-homogeneous, and samples for observational and clinical studies are confined to adolescents or adults only. Additionally, numerous studies are cross-sectional studies [25], which cannot be used to elucidate whether insomnia increases suicide risk. Hence, we employed the National Health Insurance Research Database (NHIRD) in Taiwan to conduct a retrospective cohort study of whether insomnia increases the risk of suicide attempts.

Methods

Data source

Introduced in Taiwan in 1995, the NHRID contains the medical records of all insured. The database encompasses the information of more than 99% of the 23 million people who live in Taiwan; thus, the health care information contained therein represents evidence-based data in the medicine and healthcare sector [26]. This study analyzed the 2000–2013 inpatient expenditure files and the registry for contracted medical facilities in the NHRID.

Design and sample

The retrospective cohort study design method was adopted in this study. Inpatients aged 15 years or older who were newly diagnosed with insomnia (International.

Classification of Diseases, 9th Revision, Clinical Modifications [ICD-9-CM]: 307.41, 307.42, 780.52) were allocated to the study cohort. To ensure that the patients were newly diagnosed, we also excluded patients who were diagnosed with insomnia between 1997 and 1999. The study period began on January 1, 2000 and ended on December 31, 2013. In total, 159,989 participants were included. The average of follow-up for the diagnosis of insomnia was 6.47 years. To facilitate comparison of the study cohort, propensity score-matching based on sex, age group, and date of hospitalization was performed for a 1:2 pairing to identify the reference cohort (n = 319,978 inpatients who were diagnosed as not having insomnia). Furthermore, there was no difference in the cause of hospitalization at baseline (Additional file 1: Table S1).

Outcome assessment

All research participants were observed until the incidence of suicide attempts (ICD-9-CM E code: 950–959), loss to follow up, or until the end of December 31, 2013.

Covariates of interested

The participants in this study were allocated into four groups by age: 15–24, 25–44, 45–64, and ≥ 65 years. Urbanization levels were categorized into high, moderate, and low levels of urbanization [27]. Low income included insured individuals in Category 5 (those to which laws and regulations governing social relief apply). Catastrophic illness was indicated in the copayment remarks of inpatient expenditure files. The Charlson comorbidity index (CCI) was used to weigh the 19 types of diseases by assigning each with a score of 1, 2, or 6, and the scores were summed according to whether each patient had any of these diseases [28, 29]. Because drug dependence, alcohol dependence, and mental disorders are risk factors for suicide attempts, drug dependence (ICD-9-CM 292, 304), alcohol dependence (ICD-9-CM 291, 303), and mental disorders (ICD-9-CM 290–319, excluding 291, 292, 303, 304) were incorporated in the regression model for adjustments.

Statistical analysis

All analyses were performed using SPSS 22 (SPSS, Inc., Chicago, IL, U.S.). The χ2 test and Fisher exact test were used to compare the categorical variables of the two groups, and a t-test was conducted to compare the continuous variables of the two groups. With adjustments for sex, age, low income, catastrophic illness, urbanization, CCI, drug dependence, alcohol dependence, and mental disorders, Cox proportional hazards regression analyses were performed to assess the effects of insomnia on the risk of suicide attempts and presented as hazard ratio (HR) with a 95% confidence interval (CI). Furthermore, differences in the risk of suicide attempts between the study and reference cohort were estimated using the Kaplan-Meier method with the log-rank test. A 2-tailed p-value < 0.05 was considered to indicate statistical significance.

Results

Figure 1 shows the case-screening process (inclusion and exclusion) and follow-up results as well as the cumulative risk of suicide incidence between the two groups (patients with/without insomnia). Between 2000 and 2013, 16,716,547 patients were hospitalized, 178,589 of which had insomnia. After exclusion criteria were applied (18,600 excluded), there were a total of 159,989 insomnia cases (319,978 patients were placed in the reference cohort based on 1:2 pairing) with a subsequent suicide incidence of 0.69% (1098/159,989), whereas the reference cohort exhibited a suicide incidence of 0.09% (297/319,978). The groups demonstrated significant difference (log-rank P < 0.001). In other words, the probability (risk) of suicide attempts in insomnia patients was considerably higher than that in patients without insomnia. In addition, both groups exhibited a statistically significant difference after one year follow up (Fig. 2, Table 1). Furthermore, an average follow-up period for the diagnosis of insomnia to suicide attempts was 2.38 years.
Fig. 1
Fig. 1

Flowchart of study sample selection from the National Health Insurance Research Database in Taiwan

Fig. 2
Fig. 2

Kaplan-Meier analysis of the cumulative risk of suicide attempts in 13 years of tracking stratified by insomnia with log-rank test

Table 1

Kaplan-Meier analysis of the cumulative risk of suicide attempts in 13 years of tracking stratified by insomnia with log-rank test

Insomnia

With (N = 159,989)

Without (N = 319,979)

P-value

X-year(s) of suicide attempts

Numbers of suicide attempts

1

285

101

< 0.001

2

525

157

< 0.001

3

700

195

< 0.001

4

808

222

< 0.001

5

890

248

< 0.001

6

965

265

< 0.001

7

1020

276

< 0.001

8

1052

286

0.001

9

1070

295

< 0.001

10

1084

296

< 0.001

11

1198

297

< 0.001

12

1198

297

< 0.001

13

1198

297

< 0.001

Table 2 presents the basic characteristics of the 479,967 patients at the endpoint of the follow-up process (study cohort = 159,989 insomnia patients; reference cohort = 319,978 non-insomnia patients). The study cohort exhibited a substantially higher incidence of suicide attempts compared with the reference cohort (0.7% vs 0.1%; P < 0.001). The study cohort comprised significantly higher numbers of low income patients (4.0% vs 1.5%; P < 0.001), patients with catastrophic illness (31.2% vs 19.8%; P < 0.001), and those who lived in working class urbanized townships (33.4% vs 22.3%; P < 0.001) than the reference cohort. The numbers of patients with drug dependence (1.0% vs 0.1%; P < 0.001), alcohol dependence (3.5% vs 0.7%; p < 0.001), and mental disorders (33.5% vs 7.1%; p < 0.001) and other comorbidities in the study cohort were significantly higher than those of the reference cohort.
Table 2

Characteristics of study in the endpoint

 

Total

With insomnia

Without insomnia

P-value

Variables

n

%

n

%

n

%

Total

479,967

100.0

159,989

33.3

319,978

66.7

 

Suicide attempts

      

< 0.001

 with

1395

0.3

1098

0.7

297

0.1

 

 without

478,572

99.7

158,891

99.3

319,681

99.9

 

Gender

      

0.880

 male

235,771

49.1

78,615

49.1

157,156

49.1

 

 female

244,196

50.9

81,374

50.9

162,822

50.9

 

Age group (years)

      

0.958

 15–24

15,901

3.3

5330

3.3

10,571

3.3

 

 25–44

99,058

20.6

33,030

20.6

66,028

20.6

 

 45–64

172,650

36.0

57,504

35.9

115,146

36.0

 

65

192,358

40.1

64,125

40.1

128,233

40.1

 

Low income

      

< 0.001

 yes

11,251

2.3

6441

4.0

4810

1.5

 

 no

468,716

97.7

153,548

96.0

315,168

98.5

 

Catastrophic illness

      

< 0.001

 yes

113,150

23.6

49,914

31.2

63,236

19.8

 

 no

366,817

76.4

110,075

68.8

256,742

80.2

 

Urbanization

      

< 0.001

 high

150,124

31.3

41,562

26.0

108,562

33.9

 

 medium

205,154

42.7

65,049

40.7

140,105

43.8

 

 low

124,689

26.0

53,378

33.4

71,311

22.3

 

CCI

2.36 ± 3.82

2.97 ± 4.10

2.06 ± 3.63

 

< 0.001

Drug dependence

      

< 0.001

 yes

2051

0.4

1597

1.0

454

0.1

 

 no

477,916

99.6

158,392

99.0

319,524

99.9

 

Alcohol dependence

      

< 0.001

 yes

7846

1.6

5674

3.5

2172

0.7

 

 no

472,121

98.4

154,315

96.5

317,806

99.3

 

Mental disorders

      

< 0.001

 yes

76,322

15.9

53,537

33.5

22,785

7.1

 

 no

403,645

84.1

106,452

66.5

297,193

92.9

 

P-value (category variable: Chi-square/Fisher exact test; continue variable: t-test)

Table 3 shows the univariate and multivariate analysis results of the factors of suicide attempts. After the research variables (sex, age, low income, catastrophic illness, urbanization, CCI, drug dependence, alcohol dependence, and mental disorders) were adjusted for, the risk of suicide attempts among insomnia patients was 3.533-fold that of non-insomnia patients (P < 0.001). The risk of suicide attempts among female patients was 1.522-fold (P < 0.001) that of male patients. The risk of suicide attempts among patients aged 15–24, 25–44, 45–64 years was 6.000-fold, 3.581-fold, and 1.595-fold (P < 0.001) that of patients aged 65 years or older, respectively. The risk of suicide attempts among low-income patients and patients with catastrophic illness was 1.434-fold and 1.286-fold that of their counterparts, respectively (P < 0.001). The risk of suicide attempts among patients with drug dependence and mental disorders was 1.592-fold and 4.483-fold that of their counterparts, respectively (P < 0.001).
Table 3

Factors of suicide attempts by Cox proportional hazard model analysis

Variables

Crude HR

95% CI

P-value

Adjusted HR

95% CI

P-value

Insomnia

 no

reference

   

reference

   

 yes

7.416

6.524

8.431

< 0.001

3.533

3.059

4.080

< 0.001

Gender

 female

reference

   

reference

   

 male

1.289

1.159

1.433

< 0.001

1.522

1.361

1.702

< 0.001

Age group (years)

65

reference

   

reference

   

 15–24

6.477

5.292

7.928

0.001

6.000

4.876

7.383

< 0.001

 25–44

4.909

4.238

5.687

< 0.001

3.581

3.069

4.177

< 0.001

 45–64

1.747

1.487

2.052

< 0.001

1.595

1.357

1.876

< 0.001

Low income

 no

reference

   

reference

   

 yes

3.940

3.267

4.751

< 0.001

1.434

1.184

1.736

< 0.001

Catastrophic illness

 No

reference

   

reference

   

 Yes

1.972

1.771

2.196

< 0.001

1.286

1.143

1.446

< 0.001

Urbanization

 high

reference

   

reference

   

 medium

1.045

0.916

1.193

0.510

1.013

0.887

1.157

0.847

 low

1.569

1.372

1.795

< 0.001

1.073

0.937

1.230

0.309

CCI

0.983

0.969

0.998

0.025

0.989

0.973

1.005

0.179

Drug dependence

 no

reference

   

reference

   

 yes

9.614

7.407

12.479

< 0.001

1.592

1.220

2.077

0.001

Alcohol dependence

 no

reference

   

reference

   

 yes

5.872

4.899

7.038

< 0.001

1.164

0.955

1.420

0.133

Mental disorders

 no

reference

   

reference

   

 yes

9.742

8.723

10.879

< 0.001

4.483

3.934

5.109

< 0.001

Table 4 shows the hierarchical analysis of various variables to elucidate the difference in risk of suicide attempts between insomnia and non-insomnia patients. The results indicated that (after other factors were adjusted for), in the female population, suicide risk in insomnia patients was 4.186-fold (adjusted HR = 4.186, 95% CI = 3.429–5.111, P < 0.001) that of patients without insomnia. Among patients aged 25–44 years, suicide risk in insomnia patients was 5.546-fold (adjusted HR = 5.546, 95% CI = 4.236–7.262, P < 0.001) that of patients without insomnia.
Table 4

Factors of suicide attempts stratified by variables listed in the table by Cox proportional hazard model analysis

Variables

With insomnia

Without insomnia

Ratio

Adjusted HR

95%CI

P-value

Event

PYs

Rate (per 103 PYs)

Event

PYs

Rate (per 103 PYs)

Total

1098

953,594

115.143

297

1,913,519

15.521

7.418

3.533

3.059

4.080

< 0.001

Gender

 female

633

468,954

134.981

153

941,910

16.244

8.310

4.186

3.429

5.111

< 0.001

 male

465

484,640

95.948

144

971,609

14.821

6.474

2.861

2.323

3.523

< 0.001

Age group (years)

 15–24

119

42,625

279.179

33

85,435

38.626

7.228

2.778

1.747

4.417

< 0.001

 25–44

546

198,523

275.031

80

400,512

19.974

13.769

5.546

4.236

7.262

< 0.001

 45–64

264

317,825

83.065

105

637,466

16.471

5.043

2.637

2.053

3.389

< 0.001

65

169

394,621

42.826

79

790,106

9.999

4.283

2.900

2.188

3.844

< 0.001

Low income

 no

987

915,626

107.795

288

1,884,404

15.283

7.053

3.487

3.009

4.040

< 0.001

 yes

111

37,968

292.351

9

29,115

30.912

9.458

4.069

2.012

8.228

< 0.001

Catastrophic illness

 no

635

645,939

98.306

220

1,504,259

14.625

6.722

3.769

3.171

4.479

< 0.001

 yes

463

307,655

150.493

77

409,260

18.814

7.999

2.916

2.255

3.770

< 0.001

Urbanization

 high

291

243,831

119.345

84

661,398

12.700

9.397

3.911

2.964

5.161

< 0.001

 medium

398

369,572

107.692

132

835,185

15.805

6.814

3.320

2.655

4.153

< 0.001

 low

409

340,191

120.227

81

416,936

19.427

6.188

3.355

2.592

4.342

< 0.001

Drug dependence

 no

1044

942,877

110.725

292

1,910,198

15.286

7.243

3.569

3.086

4.127

< 0.001

 yes

54

10,717

503.872

5

3321

150.557

3.347

2.079

0.817

5.286

0.207

Alcohol dependence

 no

978

916,596

106.699

288

1,899,319

15.163

7.037

3.513

3.032

4.072

< 0.001

 yes

120

36,998

324.342

9

14,200

63.380

5.117

3.844

1.936

7.634

< 0.001

Mental disorders

 no

300

618,043

48.540

181

1,763,589

10.263

4.730

4.798

3.968

5.801

< 0.001

 yes

798

335,551

237.818

116

149,930

77.369

3.074

2.223

1.823

2.711

< 0.001

Figures 3 and 4 show the interactive effects of insomnia, mental disorders, and low income after other factors were adjusted for. The risk of suicide attempts in insomnia patients without mental disorders was 4.960-fold that of patients without insomnia and mental disorders. The risk of suicide attempts in non-insomnia patients with mental disorders was 8.237-fold that of patients without insomnia and mental disorders. The risk of suicide attempts in insomnia patients with mental disorders was 18.322-fold that of patients without insomnia and mental disorders (P < 0.001) (Fig. 3). The risk of suicide attempts in non-low-income patients with insomnia was 3.521-fold that of non-insomnia patients who were not in the low-income group. The risk of suicide attempts in low-income patients without insomnia was 1.330-fold that of non-insomnia patients who were not in the low-income group. The risk of suicide attempts in low-income patients with insomnia was 5.084-fold that of non-insomnia patients who were not in the low-income group (P < 0.001) (Fig. 4).
Fig. 3
Fig. 3

Interaction for risk of suicide attempts by insomnia and mental disorders

Fig. 4
Fig. 4

Interaction for risk of suicide attempts by insomnia and low income

Discussion

Our study found that insomnia remained an independent risk factor for suicide attempts after adjustments for mental disorders, alcohol dependence, and drug dependence. To the best of our knowledge, our study is the first retrospective cohort study to use population-based data and clinical diagnosis as the criteria for determining insomnia and suicide. The findings can reinforce the deficiencies of other relevant studies.

In recent years, some studies found that mental disorders, alcohol abuse, and drug abuse do not fully mediate the association between insomnia and suicide. A study conducted in 2012 regarding members of the military in the United States reported that insomnia was an independent risk factor for suicidal ideation after adjustments for depression, hopelessness, post-traumatic stress disorder, anxiety, drug abuse, and alcohol abuse. However, there were no significant associations between insomnia and suicide attempts [15]. Different from the above study [15] using a 3-item questionnaire as the criteria for insomnia, our study used the clinical diagnosis as the criteria for determining insomnia. Another study conducted in the United States in 2016 revealed that insomnia symptoms increase the risk of suicidal ideation and attempts in adolescents with adjustments for mental disorders and substance use disorders [19]. However, the above study [19] had several limitations. First, the study was cross-sectional. No temporal relationships could be established. Second, all measures were based on self-report, thus the data were subject to response and recall bias. Therefore, based on above study [19], we established insomnia as an independent predictor of suicide attempts.

Our study found that insomnia and mental disorders have a synergistic effect on the risk of suicide attempts. The risk of suicide attempts in insomnia patients with mental disorders was 18-fold that of patients without insomnia and mental disorders. However, no comparison with past studies can be made because investigations concerning the interactive effects of insomnia and mental disorders on suicide attempts are lacking. A cross-sectional study conducted in 2018 in the United States reported that poor sleep quality will increase the risk of suicide after adjusting for depression among adolescents. However, sleep problems and depression do not interact with the risk of suicide [30]. Different from above study [30] focus on the association between sleep problems and suicide, our study focused on insomnia and suicide attempts. Therefore, it cannot be compared.

The mechanisms underlying the relationship between insomnia and suicide remain unclear. In 2013, a systematic literature review of adult insomnia and suicide conducted in the United States indicated that the mechanisms of insomnia and suicide involve both physiological and psychological dimensions [31]. The physiological mechanism includes a reduction in serotonin [32] and hypothalamic-pituitary-adrenal (HPA) axis dysfunction [33]. The psychological mechanism is associated with dysfunctional beliefs and attitudes about sleep (DBAS) [15] and depression [34]. Furthermore, a previous study found that fatigue resulting from sleep disorders may lead to hopelessness and decrease impulse control, both demonstrated risk factors for suicide [35]. The above possible mechanisms between insomnia and suicide require further studies for confirmation.

Our study determined that the risk of suicide attempts in patients with drug dependence was 1.592-fold that of patients without drug dependence. Several studies have indicated that the abuse of drugs such as marijuana [36], heroin [37, 38], and nicotine [39] are risk factors for suicide. A review article reported that 25% to 50% of people who are suicidal are dependent on alcohol or drugs, and the risk of suicide increases if these people have mental disorders [40]. A study conducted in 1995 regarding indigenous peoples in Taiwan reported that the risk of suicide in people with substance dependence and depression was 470.2-fold that of people without substance dependence and depression [41]. In our study, we found that the risk of suicide attempts in patients with both substance dependence and depression was 22.7-fold that of their counterparts who did not fact these issues, which is lower than the finding of the aforementioned study. This difference might be attributable to social group, population, and cultural discrepancies. Another study conducted in the United States in 1993 revealed that the risk of suicide in patients with substance dependence and an emotional disorder was 17.0-fold that of their counterparts [42]. By contrast, we determined that the risk of suicide attempts in patients with both substance dependence and emotional disorder was 23.4-fold that of their counterparts. Similar to the Taiwan study [41], the focus of substance abuse in this study was alcohol and drugs; however, we reported a lower rate of substance abuse (alcohol abuse = 9.2% and drug abuse = 4.3%) compared with that of [41] (alcohol abuse = 24.3% and drug abuse = 13.4%). This difference is possibly attributed to the more stringent standard of substance abuse (individuals exhibiting substance dependence) adopted in the present study.

Our study found that the risk of suicide attempts in patients with mental disorders was 4.483-fold that of patients without mental disorders. In western countries such as the United Kingdom, a study reported that 90% of suicides were associated with a history of mental disorders [43]. In Asian countries such as China, 40% to 70% of suicides were associated with a history of mental disorders [44, 45]. Multiple studies have indicated that different types of mental disorders predict different levels of suicide risk [4649]. In particular, schizophrenia has the highest risk for suicide [50]. In our study, depression had the highest risk for suicide attempts, followed by schizophrenia. Another study revealed that the risk of suicide in patients with more than one mental disorders was 1.5–2.5-fold that of patients with only one type of mental disorders [43]. We incorporated depression, anxiety, bipolar disorder, and schizophrenia for further analysis and found that for every increase in the number of mental disorders, the risk of suicide attempts increased by 0.6-fold. This finding is somewhat similar to that reported in the aforementioned study.

In 2016, a United Kingdom systematic literature review indicated that low income, low socioeconomic status, and unemployment predicted higher levels of suicidal ideation, suicidal behavior, and death by suicide [51]. Our study found that risk of suicide attempts in low-income patients was 1.434-fold that of their counterparts (adjusted HR = 1.431, 95% CI = 1.182–1.732, P < 0.001). Furthermore, the risk of suicide attempts in insomnia patients who earn low levels of income was 4.960-fold that of their counterparts (P < 0.001). This result implies that under the interactive effects of an economic stressor (low income) and insomnia, suicide became a major option for this particular population (particularly women, people aged 25–44 years, and breadwinners in the family), thereby leading to regrettable circumstances.

Our study has the following limitations. First, due to the limited types of data provided in the NHIRD, we were unable to acquire important suicide-related information (e.g., stigma, family history of suicide, occurrence of material events, and network of support). Second, our study adopted inpatient expenditure files from the NHIRD for analysis; therefore, our study findings may not be generalizable to the entire population without including outpatient cases. Third, all information was collected from medical record (NHIRD). The possibility of information bias cannot be ruled out.

Conclusions

Insomnia is a risk factor for suicide attempts and, indeed, increases the risk for suicide. In addition, low income, drug dependence, and mental disorders are risk factors for suicide attempts. Female patients and those aged 25–44 years are high-risk groups. Risk of suicide attempts is higher in low-income individuals with insomnia and mental disorders. Clinicians should pay attention to the mental status and income level of insomnia patients and implement early suicide prevention intervention. If members of the general public have friends who suffer from insomnia, they should pay attention to the mental and financial status of their friends in order to reduce the probability of suicide.

Abbreviations

CCI: 

The Charlson comorbidity index

CI: 

Confidence interval

HR: 

Hazard ratio

ICD-9-CM: 

The International Classification of Diseases, 9th Revision, Clinical Modifications

NHIRD: 

National Health Insurance Research Database

WHO: 

World Health Organization

Declarations

Acknowledgments

This study was supported by grants from Tri-service Hospital Research Foundation (TSGH-C107-004), and the sponsor has no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Availability of data and materials

Data are from the National Health Institute Research Database (NHIRD), which are available to researchers in Taiwan and have been extensively used in epidemiologic studies. It is permissible to use these data for academic purposes only after providing proof to National Health Research Institute. Thus, the data cannot be made publicly available. Data requests may be sent to National Health Institute Research Database (http://nhird.nhri.org.tw/) at nhird@nhri.org.tw.

Authors’ contributions

CCH, LCH and CWC contributed to the study design. Data analyses and interpretation were performed by LHT, PHJ, WCC, CWL and CWC. LHT, LCH and CWC drafted and revised the manuscript. All authors read and approved the final manuscript.

Ethics approval and consent to participate

The study protocol was approved by the approval institutional review board, Tri-Service General Hospital. (TSGHIRB No. 1–106–05-169).

Competing interests

The authors declare that they have no competing interests.

Publisher’s Note

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Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

Authors’ Affiliations

(1)
National Defense Medical Center, School of Public Health 4325R, No. 161, Section 6, Min-Chuan East Road, Neihu District, Taipei City, 11490, Taiwan, Republic of China
(2)
National Defense Medical Center, Graduate Institute of Life Sciences 7115R, No. 161, Section 6, Min-Chuan East Road, Neihu District, Taipei City, 11490, Taiwan, Republic of China
(3)
Department of Family and Community Medicine, National Defense Medical Center, Tri-Service General Hospital Taipei, No. 325, Section 2, Cheng-Kung Road, Taipei City, 11490, Taiwan, Republic of China
(4)
Department of Medical Research 7115R, National Defense Medical Center, Tri-Service General Hospital Taipei, No. 325, Section 2, Cheng-Kung Road, Taipei City, 11490, Taiwan, Republic of China

References

  1. World Health Organization. Suicide: Fact sheet. 2017 [http://www.who.int/mediacentre/factsheets/fs398/en/].Google Scholar
  2. Nock MK, Borges G, Bromet EJ, Cha CB, Kessler RC, Lee S. Suicide and suicidal behavior. Epidemiol Rev. 2008;30:133–54.View ArticlePubMedPubMed CentralGoogle Scholar
  3. Yoshimasu K, Kiyohara C, Miyashita K. Stress research Group of the Japanese Society for hygiene. Suicidal risk factors and completed suicide: meta-analyses based on psychological autopsy studies. Environ Health Prev Med. 2008;13(5):243–56.View ArticlePubMedPubMed CentralGoogle Scholar
  4. World Health Organization. Preventing suicide: A global imperative. 2014 [http://www.who.int/mental_health/suicide-prevention/world_report_2014/en/].Google Scholar
  5. Ministry of Health and Welfare, Taiwan. 2016 statistical results on causes of death in Taiwan. 2016 [https://www.mohw.gov.tw/cp-16-33598-1.html].Google Scholar
  6. Unbehaun T, Spiegelhalder K, Hirscher V, Riemann D. Management of insomnia: update and new approaches. Nat Sci Sleep. 2010;28(2):127–38.Google Scholar
  7. Doghramji K. The epidemiology and diagnosis of insomnia. Am J Manag Care. 2006;12(Suppl 8):S214–20.PubMedGoogle Scholar
  8. Cho YW, Shin WC, Yun CH, Hong SB, Kim J, Earley CJ. Epidemiology of insomnia in korean adults: prevalence and associated factors. J Clin Neurol. 2009;5(1):20–3.View ArticlePubMedPubMed CentralGoogle Scholar
  9. Chan-Chee C, Bayon V, Bloch J, Beck F, Giordanella JP, Leger D. Epidemiology of insomnia in France. Rev Epidemiol Sante Publique. 2011;59(6):409–22.View ArticlePubMedGoogle Scholar
  10. Ikeda M, Kaneita Y. The newest epidemiology trend of insomnia. Nihon Rinsho. 2014;72(3):573–7.PubMedGoogle Scholar
  11. Taiwan Society of Sleep Medicine. 2017 trend in prevalence of sleep problems in Taiwan: a 10-years cross sectional study. 2017 [http://www.tssm.org.tw/file/1494489550.pdf].Google Scholar
  12. Chung WS, Li FC, Ho FM. Classification and Treatment of insomnia. Taiwan Med J. 2013;56(12):642–5.Google Scholar
  13. Nadorff MR, Nazem S, Fiske A. Insomnia symptoms, nightmares, and suicidal ideation in a college student sample. Sleep. 2011;34(1):93–8.View ArticlePubMedPubMed CentralGoogle Scholar
  14. Nadorff MR, Fiske A, Sperry JA, Petts R, Gregg JJ. Insomnia symptoms, nightmares, and suicidal ideation in older adults. J Gerontol B Psychol Sci Soc Sci. 2013;68(2):145–52.View ArticlePubMedGoogle Scholar
  15. Ribeiro JD, Pease JL, Gutierrez PM, Silva C, Bernert RA, Rudd MD, et al. Sleep problems outperform depression and hopelessness as cross-sectional and longitudinal predictors of suicidal ideation and behavior in young adults in the military. J Affect Disord. 2012;136(3):743–50.View ArticlePubMedGoogle Scholar
  16. Richardson JD, Thompson A, King L, Corbett B, Shnaider P, St Cyr K, et al. Insomnia, psychiatric disorders and suicidal ideation in a National Representative Sample of active Canadian forces members. BMC Psychiatry. 2017;17(1):211.View ArticlePubMedPubMed CentralGoogle Scholar
  17. Hall RC, Platt DE, Hall RC. Suicide risk assessment: a review of risk factors for suicide in 100 patients who made severe suicide attempts. Evaluation of suicide risk in a time of managed care. Psychosomatics. 1999;40(1):18–27.View ArticlePubMedGoogle Scholar
  18. Kay DB, Dombrovski AY, Buysse DJ, Reynolds CF, Begley A, Szanto K. Insomnia is associated with suicide attempt in middle-aged and older adults with depression. Int Psychogeriatr. 2016;28(4):613–9.View ArticlePubMedGoogle Scholar
  19. Wong MM, Brower KJ, Craun EA. Insomnia symptoms and suicidality in the National Comorbidity Survey - adolescent supplement. J Psychiatr Res. 2016;81:1–8.View ArticlePubMedPubMed CentralGoogle Scholar
  20. Fujino Y, Mizoue T, Tokui N, Yoshimura T. Prospective cohort study of stress, life satisfaction, self-rated health, insomnia, and suicide death in Japan. Suicide Life Threat Behav. 2005;35(2):227–37.View ArticlePubMedGoogle Scholar
  21. Goldstein TR, Bridge JA, Brent DA. Sleep disturbance preceding completed suicide in adolescents. J Consult Clin Psychol. 2008;76(1):84–91.View ArticlePubMedPubMed CentralGoogle Scholar
  22. Bjorngaard JH, Bjerkeset O, Romundstad P, Gunnell D. Sleeping problems and suicide in 75,000 Norwegian adults: a 20 year follow-up of the HUNT I study. Sleep. 2011;34(9):1155–9.View ArticlePubMedPubMed CentralGoogle Scholar
  23. Bertolote JM, Fleischmann A, De Leo D, Wasserman D. Psychiatric diagnoses and suicide: revisiting the evidence. Crisis. 2004;25(4):147–55.View ArticlePubMedGoogle Scholar
  24. Bernert RA, Joiner TE, Cukrowicz KC, Schmidt NB, Krakow B. Suicidality and sleep disturbances. Sleep. 2005;28(9):1135–41.View ArticlePubMedGoogle Scholar
  25. Pigeon WR, Pinquart M, Conner K. Meta-analysis of sleep disturbance and suicidal thoughts and behaviors. J Clin Psychiatry. 2012;73(9):e1160–7.View ArticlePubMedGoogle Scholar
  26. National Health Research Institutes, Taiwan. The National Health Insurance Research Database: background. 2003 [https://nhird.nhri.org.tw/en/index.html].Google Scholar
  27. Liu CY, Hung YT, Chuang YL, Chen YJ, Weng WS, Liu JS, et al. Incorporating development stratification of Taiwan townships into sampling Design of Large Scale Health Interview Survey. J Health Manag. 2006;4(1):1–22.Google Scholar
  28. Charlson ME, Pompei P, Ales KL, MacKenzie CR. A new method of classifying prognostic comorbidity in longitudinal studies: development and validation. J Chronic Dis. 1987;40(5):373–83.View ArticlePubMedGoogle Scholar
  29. Deyo RA, Cherkin DC, Ciol MA. Adapting a clinical comorbidity index for use with ICD-9-CM administrative databases. J Clin Epidemiol. 1992;45(6):613–9.View ArticlePubMedGoogle Scholar
  30. Becker SP, Dvorsky MR, Holdaway AS, Luebbe AM. Sleep problems and suicidal behaviors in college students. J Psychiatr Res. 2018;99:122–8.View ArticlePubMedGoogle Scholar
  31. McCall WV, Black CG. The link between suicide and insomnia: theoretical mechanisms. Curr Psychiatry Rep. 2013;15(9):389.View ArticlePubMedPubMed CentralGoogle Scholar
  32. Elmenhorst D, Kroll T, Matusch A, Bauer A. Sleep deprivation increases cerebral serotonin 2A receptor binding in humans. Sleep. 2012;35(12):1615–23.View ArticlePubMedPubMed CentralGoogle Scholar
  33. Bonnet MH, Arand DL. 24-hour metabolic rate in insomniacs and matched normal sleepers. Sleep. 1995;18(7):581–8.View ArticlePubMedGoogle Scholar
  34. Kitamura S, Hida A, Watanabe M, Enomoto M, Aritake-Okada S, Moriguchi Y, et al. Evening preference is related to the incidence of depressive states independent of sleep-wake conditions. Chronobiol Int. 2010;27(9–10):1797–812.View ArticlePubMedGoogle Scholar
  35. Joiner TE, Brown JS, Wingate LR. The psychology and neurobiology of suicidal behavior. Annu Rev Psychol. 2005;56:287–314.View ArticlePubMedGoogle Scholar
  36. Borges G, Benjet C, Orozco R, Medina-Mora ME, Menendez D. Alcohol, cannabis and other drugs and subsequent suicide ideation and attempt among young Mexicans. J Psychiatr Res. 2017;91:74–82.View ArticlePubMedGoogle Scholar
  37. Kazour F, Soufia M, Rohayem J, Richa S. Suicide risk of heroin dependent subjects in Lebanon. Community Ment Health J. 2016;52(5):589–96.View ArticlePubMedGoogle Scholar
  38. Darke S, Ross J, Marel C, Mills KL, Slade T, Burns L, et al. Patterns and correlates of attempted suicide amongst heroin users: 11-year follow-up of the Australian treatment outcome study cohort. Psychiatry Res. 2015;227(2–3):166–70.View ArticlePubMedGoogle Scholar
  39. Bohnert KM, Ilgen MA, McCarthy JF, Ignacio RV, Blow FC, Katz IR. Tobacco use disorder and the risk of suicide mortality. Addiction. 2014;109(1):155–62.View ArticlePubMedGoogle Scholar
  40. Schneider B. Substance use disorders and risk for completed suicide. Arch Suicide Res. 2009;13(4):303–16.View ArticlePubMedGoogle Scholar
  41. Cheng AT. Mental illness and suicide. A case-control study in East Taiwan. Arch Gen Psychiatry. 1995;52(7):594–603.View ArticlePubMedGoogle Scholar
  42. Brent DA, Perper JA, Moritz G, Allman C, Friend A, Roth C, et al. Psychiatric risk factors for adolescent suicide: a case-control study. J Am Acad Child Adolesc Psychiatry. 1993;32(3):521–9.View ArticlePubMedGoogle Scholar
  43. Cavanagh JT, Carson AJ, Sharpe M, Lawrie SM. Psychological autopsy studies of suicide: a systematic review. Psychol Med. 2003;33(3):395–405.View ArticlePubMedGoogle Scholar
  44. Zhang J, Xiao S, Zhou L. Mental disorders and suicide among young rural Chinese: a case-control psychological autopsy study. Am J Psychiatry. 2010;167(7):773–81.View ArticlePubMedPubMed CentralGoogle Scholar
  45. Jia CX, Wang LL, Xu AQ, Dai AY, Qin P. Physical illness and suicide risk in rural residents of contemporary China: a psychological autopsy case-control study. Crisis. 2014;35(5):330–7.View ArticlePubMedGoogle Scholar
  46. Indu PS, Anilkumar TV, Pisharody R, Russell PSS, Raju D, Sarma PS, et al. Prevalence of depression and past suicide attempt in primary care. Asian J Psychiatr. 2017;27:48–52.View ArticlePubMedGoogle Scholar
  47. Thibodeau MA, Welch PG, Sareen J, Asmundson GJ. Anxiety disorders are independently associated with suicide ideation and attempts: propensity score matching in two epidemiological samples. Depress Anxiety. 2013;30(10):947–54.View ArticlePubMedGoogle Scholar
  48. McGrady A, Lynch D, Rapport D. Psychosocial factors and comorbidity associated with suicide attempts: findings in patients with bipolar disorder. Psychopathology. 2017;50(2):171–4.View ArticlePubMedGoogle Scholar
  49. Jakhar K, Beniwal RP, Bhatia T, Deshpande SN. Self-harm and suicide attempts in schizophrenia. Asian J Psychiatr. 2017;30:102–6.View ArticlePubMedGoogle Scholar
  50. Limosin F, Loze JY, Philippe A, Casadebaig F, Rouillon F. Ten-year prospective follow-up study of the mortality by suicide in schizophrenic patients. Schizophr Res. 2007;94(1–3):23–8.View ArticlePubMedGoogle Scholar
  51. Iemmi V, Bantjes J, Coast E, Channer K, Leone T, McDaid D, et al. Suicide and poverty in low-income and middle-income countries: a systematic review. Lancet Psychiatry. 2016;3(8):774–83.View ArticlePubMedGoogle Scholar

Copyright

© The Author(s). 2018

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