Participants and procedures
A two-stage stratified cluster sampling method was used to select research sites. Three provinces were randomly selected from the GDP ranking of the top 10, 11-20, 21-31 provinces in mainland China these are Shandong, Hunan, and Guangxi. Counties were divided into three strata based on the average income within each province. Counties were randomly selected from each stratum, and a total of 12 counties were selected as research sites. A case-control psychological autopsy study was devised and implemented from June 2014 to September 2015 [13, 14]. A detailed description of the sampling methods, participants, and interview procedures was reported in our previous publication [15].
In each of the selected counties, suicide cases aged 60 years and older were collected consecutively from the death certification system. The controls were community members matched 1:1 with suicide case by age (± 3 years), gender, and location. For every participant, two informants were selected to obtain the data related to them. Generally, the first informant was a family member, and the second informant was a friend, a neighbor, or other relevant people. The survey was conducted through face-to-face interview with an average interview time of 90 minutes. For each pair of suicide and control, 4 interviews were conducted; a total of 968 interviews were completed for 242 pairs.
The investigators consisted of teachers and graduate students from Shandong University, Central South University and Guangxi Medical University. All investigators were trained intensively for 10 days in a standardized way on the instruments and the skills necessary for the interview.
The study was approved by the Institutional Review Board of the Shandong University, Central South University, and Guangxi Medical University. The aim and procedure of the research were explained to all participants. Written informed consent was obtained before interviews were conducted.
Measurements
Demographic characteristics
Demographic variables included age (in years), gender (male/female), marital status (stable/unstable), family income (Yuan), presence of physical disease (yes/no), presence of mental disorder (yes/no), living alone (yes/no) and left behind by children (yes/no). In the study, people who were married and living with a spouse, or cohabitation with a partner were classified as “stable marital status”, while people with other marital status were classified as “unstable”.
Stressful life events for the older adults
Stressful life events were measured by the Life Events Scale for the Elderly (LESE), which was developed specifically for older Chinese adults [16]. LESE is a valid and reliable scale among the older adults in general, and for older adults who died by suicide in particular [16, 17]. A total of 46 life events were categorized into three separate categories: (1) Health/Hospital (16 items); (2) Family/Home (18 items); and (3) Friends/Relationships (12 items). Each life event was assessed by five questions: (1) The date it happened (never occurred, one month, one year, and more than one year ago); (2) Whether it was positive or negative for the participant; (3) The effect on participants’ mental health, measured by a five-point Likert scale from 1 = no impact, to 5 = very severe impact; (4) The duration of the event (three months, six months, one year, and more than one year); and (5) The number of times it happened.
It should be noted that both positive and negative life events can cause a psychological stress response in participants. Therefore, stressful life events included positive as well as negative life events. In this study, stressful life events that happened within one month before suicide/interview for living control were converted to recent stressful life event. Stressful life events that happened within one year (excluding those within one month) or more than one year were converted to long-term stressful life events.
Statistical analysis
The information provided by two informants was combined as proxy data for the suicides and controls. The demographic characteristics based on the information provided by the first informant was used. Answers associated with an increased risk of suicide were used when two informants reported differently for each item of LESE. The rationale for this practice is that a targeting behavior may exist if one of the two informants has observed it.
All participants were divided into two groups using the median number of stressful life events. The t-test and chi-squared test were used to compare the differences in demographic characteristics between the older adults who experienced fewer life events and more life events, for both among suicides and living controls. A chi-squared test was used to analyze the incidence of 46 stressful life events between suicides and controls. A chi-squared test was also used to compare the frequency of the top 10 stressful life events between males and females among the suicide cases. Logistic regression analysis was used to explore the relationship between stressful life events and suicide.
All analyses were performed using SPSS 24.0 for Windows (SPSS Inc, Chicago, IL). In this study, statistical significance was set as P less than 0.05.