Chronic Disease, Disability, Psychological Distress and Suicide Ideation among Rural Elderly: Results from a Population Survey in Shandong

Objective: Suicide is a major public health and social problem in contemporary societies. Previous studies showed that the older the seniors were, the more likely it was that they would experience disability, chronic disease, or both. The objective of this study was to examine the joint effects of chronic disease and physical disability on suicide ideation while controlling for psychological distress among the rural elderly living in Shandong Province, China. Method: A total of 5514 rural elderly individuals (60+) living in Shandong Province, China were included in this study. Suicidal ideation was assessed by using questions from the National Comorbidity Survey (NCS). Multiple logistic analyses were performed to examine the factors associated with suicide ideation. A path analysis was conducted to test the direct and indirect effects of chronic disease and of activity of daily living (ADL) limitation on suicide ideation while controlling for psychological distress. Results: The prevalence of suicide ideation among the rural elderly in Shandong, China was 11.0%. Psychological distress had the strongest direct (β = 0.392) and total effect (β = 0.392), chronic disease (β = −0.034; β = −0.063) had both direct and indirect impacts, and ADL (β = 0.091) had indirect impacts on suicide ideation. Psychological distress was a mediator between chronic disease, ADL limitation, and suicide ideation. Conclusions: Psychological distress was the greatest influencing factor of suicide ideation among the rural elderly, followed by chronic disease and disability. Effective intervention measures should be taken to facilitate the early detection of psychological distress in clinical practice among the rural elderly.


Introduction
Suicide is a major public health and social problem in contemporary societies, and lays a huge economic, social, and psychological burden on individuals, families, communities, and countries. Every year, around 800,000 people worldwide die due to suicide, which corresponds to an adjusted global rate of 11.4/100,000 in 2012 [1]. China, where suicide is ranked as the fifth leading cause of death, accounts for an estimated 22% of global suicides, or roughly 200,000 deaths per year [2].
Although the suicide rates in China have decreased in the past two decades [3], the peak for the elderly has remained relatively unchanged and has even slightly increased in recent years, making 2 of 10 suicide among the elderly in China a prevalent public health problem which we should address [4]. Some previous studies conducted in China and other countries have indicated that the suicide rate was higher among the elderly [5,6]. In addition, the rural elderly suicide rates are three to five times higher than those in urban areas [7,8]. Suicide ideation is an important risk factor for attempted and completed suicide [9]. For suicide ideation, S. H. Kim found that chronic illnesses and functional limitations were associated with an increased risk of suicide ideation [10]. H. Xu, L. Qin, and J. Wang et al. had similar results [11]. Chronic disease and disability were also determinants of "high" psychological distress [12,13]. Social demographics and other factors such as depression and insomnia have been associated with suicide ideation [14][15][16].
Previous studies have identified the relationship between chronic disease, disability, psychological distress, and suicide ideation. However, there have been few ideas concerning the direct and indirect effects of activity of daily living (ADL) limitation, chronic disease, and psychological distress on suicide ideation. The purpose of the current study is to examine the joint effects of chronic disease and physical disability on suicide ideation among the elderly while controlling for psychological distress. Specifically, chronic disease has a direct effect on suicide ideation, and both chronic disease and physical disability have an indirect effect on suicide ideation through psychological distress. In particular, the current study will address the following research questions and hypotheses. First, chronic disease and physical disability are associated with suicide ideation. Second, chronic disease has a partial direct effect and a partial indirect effect on suicide ideation through psychological distress. Third, physical disability has a full indirect effect on suicide ideation through psychological distress.

Settings and Participants
The design of the study consisted of face-to-face interviews using a structured questionnaire. This study was collected from the 2017 Survey of the Shandong Elderly Family Health Service, which was conducted by Shandong University. Stratified multi-stage random sampling was applied: in the first stage, six counties were selected from 137 counties as the primary sampling units (PSUs) throughout the eastern, central, and western regions of Shandong Province (which were divided into three districts and three counties that represented urban and rural areas, respectively). From each PSU, 18 villages in rural areas and 18 communities in suburban and urban areas were selected in the second stage as the secondary sampling units (SSUs). In the third stage, based on the roster of the residents by age and the total elderly population of each selected site provided by the local residential committee, an average of 66 individuals were stratified and randomly selected from each SSU, making up the total sample. The eligible participants for this survey were those aged 60 and above with local household registrations at the time of the interview. Initially, 7088 elderly individuals were selected and interviewed. Of these, 18 did not complete the survey because of an uncompleted questionnaire or an obvious logical error in the questionnaire. Finally, a total of 7070 individuals were included in the sample (Figure 1). Our current study focused on respondents who answered the question "Have you ever seriously thought about committing suicide?" among the rural elderly (n = 5514).

Dependent Variable
Suicide ideation was assessed by using a question from the baseline National Comorbidity Survey (NCS) [17]: "Have you ever seriously thought about committing suicide?" The question was designed to ask whether they had experienced this idea in their lifetime. For the purpose of the analysis, a positive response was considered to indicate the presence of suicide ideation.

Dependent Variable
Suicide ideation was assessed by using a question from the baseline National Comorbidity Survey (NCS) [17]: "Have you ever seriously thought about committing suicide?" The question was designed to ask whether they had experienced this idea in their lifetime. For the purpose of the analysis, a positive response was considered to indicate the presence of suicide ideation.

Physical Disability
The elderly individual's physical disability was measured using the ADL Scale, including ADL subscales [18] and instrumental activity of daily living (IADL) subscales [19]. The ADL subscale assesses six types of ability: feeding, dressing, bathing, toileting, grooming, and locomotion. The IADL subscale evaluates the ability to perform eight types of more complex activities, like using a telephone, using transportation, and shopping. Scores for performing activities range from 1 to 4 (1 point for each activity performed without help and 4 points for each activity that the individual is unable to perform). The maximum score is 56 (higher scores indicate greater dependence). Edwards confirmed the ADL scales in a Brazilian study, showing a Cronbach's α of 0.96-0.99 [20]. The Cronbach's α for the ADL was 0.93 in this sample.

Psychological Distress
Kessler 10 (K10) is a recognized and validated measure of psychological distress, in which respondents report how frequently they experienced specified symptoms of psychological distress [21,22]. An individual's sense of psychological distress is evaluated against ten items on a self-report questionnaire. Each item is rated on a five-point scale with numerical values assigned to the responses (none of the time, a little of the time, some of the time, most of the time, and all the time). The ratings are summed to yield a total score, with higher scores indicating higher levels of psychological distress. The scale's internal consistency, as assessed by Cronbach's α, was 0.87. The Cronbach's α for the K10 was 0.92 in this sample.

Socio-Demographic Characteristics
The socio-demographic characteristics included chronic diseases in the past 6 months, gender, age, education level, residential status, self-rated health, and family relationship. Chronic disease was coded as yes and no in the past 6 months. Gender was coded as male and female. Education

Physical Disability
The elderly individual's physical disability was measured using the ADL Scale, including ADL subscales [18] and instrumental activity of daily living (IADL) subscales [19]. The ADL subscale assesses six types of ability: feeding, dressing, bathing, toileting, grooming, and locomotion. The IADL subscale evaluates the ability to perform eight types of more complex activities, like using a telephone, using transportation, and shopping. Scores for performing activities range from 1 to 4 (1 point for each activity performed without help and 4 points for each activity that the individual is unable to perform). The maximum score is 56 (higher scores indicate greater dependence). Edwards confirmed the ADL scales in a Brazilian study, showing a Cronbach's α of 0.96-0.99 [20]. The Cronbach's α for the ADL was 0.93 in this sample.

Psychological Distress
Kessler 10 (K10) is a recognized and validated measure of psychological distress, in which respondents report how frequently they experienced specified symptoms of psychological distress [21,22]. An individual's sense of psychological distress is evaluated against ten items on a self-report questionnaire. Each item is rated on a five-point scale with numerical values assigned to the responses (none of the time, a little of the time, some of the time, most of the time, and all the time). The ratings are summed to yield a total score, with higher scores indicating higher levels of psychological distress. The scale's internal consistency, as assessed by Cronbach's α, was 0.87. The Cronbach's α for the K10 was 0.92 in this sample.

Socio-Demographic Characteristics
The socio-demographic characteristics included chronic diseases in the past 6 months, gender, age, education level, residential status, self-rated health, and family relationship. Chronic disease was coded as yes and no in the past 6 months. Gender was coded as male and female. Education level was coded as illiteracy, primary, and middle or above. Residential status was coded as single and couple. Self-rated health was coded as good and bad. Family relationship was coded as good and bad.

Statistical Analysis
All statistical analyses were performed using SPSS 22.0 (IBM Corp, Armonk, NY, USA) and Amos 21.0 (IBM Corp, Armonk, NY, USA). t-test or χ 2 test was used to compare the difference in continuous or categorical variables. Logistic regression analysis was performed to examine the association of suicide ideation with some variables. Gender, ADL, chronic disease, and psychological distress were chosen as the independent variables in a path analysis model. The reported CI was calculated at the 95% level, and statistical significance was set at the 5% level. Table 1 displays the socio-demographic details of the rural elderly about suicide ideation. A total of 5514 rural elderly individuals responded to the study. About 11.0% (n = 605) acknowledged suicide ideation (see Table 1). The age of the participants ranged from 60 to 101 (mean= 69.72; SD = 6.52), 57.1% were female, 80.8% lived with a spouse, and 39.2% was illiterate. Of the participants, 94.6% had a harmonious family. Furthermore, those people who had chronic disease accounted for 68.8%, whose self-rated health status was good accounted for 52.2%. The study compared participants in terms of the variables of age, gender, education level, residential status, self-rated health, family relationship, and chronic disease status in relation to suicide ideation. The participants differed significantly from each other in relation to suicide ideation.

Logistic Regression Analysis
The results of the logistic regression analysis of suicide ideation are shown in Table 2. ADL and chronic disease were significantly associated with suicide ideation (Models 1 and 2). When we adjusted for psychological distress, the OR of ADL changed from 1.03 to 0.99 (Models 1 and 3) and the chronic disease status changed from 1.71 to 1.14 (Models 2 and 4). Age (OR = 0.97), education (primary OR = 0.73, middle or above OR = 0.49) and family relationship (OR = 1.39) were significantly associated with suicide ideation among the rural elderly in Shandong, China (Model 5).  Figure 2 demonstrates the interaction between ADL limitation, chronic disease, psychological distress, and suicide ideation. Standardized regression coefficients are presented on each arrow. Using a path analysis, we found that psychological distress had a direct impact on suicide ideation. The influences of ADL on suicide ideation were mediated by psychological distress. Chronic disease had both direct and indirect effects on suicide ideation. The model had an absolute fit index (GFI) of 1.000, a simple fit index (P) of 0.866, a comparative fit index (CFI) of 1.000, and a root mean square error of approximation (RMSEA) of 0.000. Four fit indices indicated that the final path model adequately represented the data.

The Mediating Effect of Psychological Distress between ADL Limitation and Suicide Ideation
(primary OR = 0.73, middle or above OR = 0.49) and family relationship (OR = 1.39) were significantly associated with suicide ideation among the rural elderly in Shandong, China (Model 5). Figure 2 demonstrates the interaction between ADL limitation, chronic disease, psychological distress, and suicide ideation. Standardized regression coefficients are presented on each arrow. Using a path analysis, we found that psychological distress had a direct impact on suicide ideation. The influences of ADL on suicide ideation were mediated by psychological distress. Chronic disease had both direct and indirect effects on suicide ideation. The model had an absolute fit index (GFI) of 1.000, a simple fit index (P) of 0.866, a comparative fit index (CFI) of 1.000, and a root mean square error of approximation (RMSEA) of 0.000. Four fit indices indicated that the final path model adequately represented the data. Table 3 presents the total, direct, and indirect effects of the variables on suicidal ideation. The total effects are the sum of the direct and indirect effects. Indirect effects represent the effects of one variable on another variable through indirect routes. We found that the value of standardized total effects of psychological distress was (0.392), while chronic disease was 0.096 and ADL limitation was 0.091.

Figure 2.
Direct and indirect effects of chronic disease, disability, and psychological distress on suicide ideation among the rural elderly in Shandong, China (OR and its 95% CI). ** p < 0.01, *** p < 0.001. Figure 2. Direct and indirect effects of chronic disease, disability, and psychological distress on suicide ideation among the rural elderly in Shandong, China (OR and its 95% CI). ** p < 0.01, *** p < 0.001. Table 3 presents the total, direct, and indirect effects of the variables on suicidal ideation. The total effects are the sum of the direct and indirect effects. Indirect effects represent the effects of one variable on another variable through indirect routes. We found that the value of standardized total effects of psychological distress was (0.392), while chronic disease was 0.096 and ADL limitation was 0.091.

Discussion
The lifetime prevalence of suicide ideation among the rural elderly was 11.0% (605 of 5514) in the current study. It was lower than the lifetime prevalence of 13.0% among the rural elderly living in Hunan Province, China [23]. It was higher than the reported rates among the elderly in Shandong, China (4.2%) [24], Hong Kong (5.5%) [25], Taiwan (6.1%) [26], and Canada (8.4%) [27]. Because of the different levels of research backgrounds and the time point of definition, the prevalence of suicide ideation varied widely.
Psychological distress had the most powerful and direct relationship with suicide ideation in the current study. This is similar to previous studies. For example, one study found that psychological distress had a direct and mediating role in suicidal patients among adolescents [28], which was also a predictor for suicide ideation among the community-dwelling elderly [29]. This correlation was stronger in older people than in younger people [27]. The K10 scale was used to represent psychological distress. Psychological distress was an effective screener to measure suicide ideation, which was composed of two primary factors (depression and anxiety) [30,31].
In the current study, when psychological conditions were controlled, ADL limitation had little direct effect on suicide ideation. But suicide ideation was indirectly accompanied by psychological distress, which implies that psychological distress mediates the process of developing suicide ideation. Studies demonstrated that disability was significantly associated with suicidal ideation, particularly for the elderly [32,33]. Functional disability as a determinant of "high" psychological distress has been demonstrated by several studies [34]. One possible explanation for the mediating role of psychological distress was the lack of their daily housework and economic resources.
This study shows that chronic disease had both direct and indirect impacts on suicide ideation. Studies have found a positive association between chronic disease and suicide, such as coronary heart disease, diabetes and combined illness, etc. [35][36][37], which was similar to the findings of our study. Using a path analysis, we proposed that chronic disease would affect suicide ideation directly or through psychological distress, and we found that it had both direct and indirect effects on suicide ideation among the elderly. Some previous studies demonstrated that chronic disease was associated with psychological distress among the elderly [38][39][40]. Furthermore, psychological distress was found to be a predictor for suicide ideation among the elderly [41]. One possible explanation was that high levels of disease burden were more sensitive to psychological distress. In addition, the internet might also have positive effects on particularly older people who obtain information about their (chronic) diseases that contribute to their stress and access social support that is beneficial to their mental health [42][43][44]. There is a considerable body of research on the effects, both positive and negative, of media on suicide among different age groups [45][46][47][48][49]. The implication of this finding was that chronic disease may not only directly affect, but also prevent suicide ideation by reducing the psychological distress among elderly people.
Age, education, and family relationship were significantly associated with suicide ideation in our study, but we mainly studied the relationship between chronic disease, ADL limitation, psychological distress, and suicide ideation.

Strength and Limitations
The large sample size (n > 5000) provided strong statistical support for our study. However, the study still has several limitations, as indicated below. First, this study was based on a house-to-house interview, but village clinic interviews and house-to-house interviews were combined. The results may be biased because the individuals who arrived to the clinics usually had normal ADL, whereas the elderly with ADL limitation may not have been able to be interviewed. Second, information, including suicide ideation and health status, was self-reported, inevitably leading to the possibility of subjective bias. Third, we mainly focused on the risk factors for suicide ideation in the current study, and gave little consideration to the relationship between suicide ideation and attempted and completed suicide. Fourth, the dependent variable was lifetime suicide ideation. Chronic disease was diagnosed clearly by the medical staff in the first half of the investigation, but this study could not determine if suicide ideation occurred before, after, or both before and after experiencing psychological distress and health problems. Finally, the ORs for all of these variables were low. There were many statistically significant findings, but the effects noted in the data provided a limited ability to predict suicide ideation.

Conclusions
Psychological distress was found to have the greatest total and direct effect on suicide ideation among rural elderly, followed by chronic disease and disability. Chronic disease had a partial direct effect and a partial indirect effect on suicide ideation through psychological distress, but disability only had an indirect effect on suicide ideation through psychological distress. These findings imply a