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 which are Shandong, Hunan, and Guangxi. Counties were divided into three stratums based on average income within each province. Counties were randomly selected from each stratum, and 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].
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 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 important people. For each pair of suicide and control, 4 interviews were conducted, a total of 968 interviews were completed for 242 pair. The survey was conducted through face-to-face interview with an average interview time of 90 minutes.
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 of 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.
Demographic variables included age (in years), gender (male/female), marital status (stable/unstable), family income (yuan), if having a physical disease (yes/no), if having a mental disorder (yes/no), if 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 event for the elderly
Stressful life events were measured by the Life Events Scale for the Elderly (LESE), which was developed specifically for older Chinese adults . LESE is a valid and reliable scale among the elderly generally, and elderly people who died by suicide in particular [15, 16]. A total of 46 life events were categorized into three separate categories: (1) Health/Hospital (16 items); (2) Family/Home (18 items); (3) Friends/Relationships (12 items). Each life event was assessed by five questions: (1) The date it happened (never occur, one month, one year, and more than one year); (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.
Both positive and negative life events can cause a psychological stress response to the participants. Stressful life events included positive life events as well as negative. In this study, stressful life events happened within one month were converted to recent stressful life event. Stressful life events happened within one year (excluding one month) or more than one year were converted to long-term stressful life events.
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 relied on. Answers which were 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 as long as 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-square test were used to compare the difference of demographic characteristics between the elderly who experienced fewer life events and more life events both among suicides and living controls. Chi-square test was used to analyze the incidence of 46 stressful life events between suicides and controls. Chi-square test was also used to compare the frequency of the top 10 stressful life events between males and females among 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 the study, statistical significance was determined if P less than 0.05.