Participants and procedures
The cross-sectional study was conducted in two general hospitals (the Second Affiliated Hospital of Dalian Medical University and the Zhongshan Affiliated Hospital of Dalian University) in Dalian, a metropolitan region located on the northeast coast of China. Dalian’s gross domestic product (GDP) ranked 26th nationally in 2018, falling into the medium level among all the cities in China. Patients who were hospitalized in the oncology settings at the two hospitals were consecutively recruited from January to December 2015. Eligibility criteria included 1) diagnosis of cancer by pathology or cytology; 2) age of 18 years or older; 3) patient awareness of their own cancer diagnosis; 4) provision of written informed consent. Exclusion criteria were 1) inability to participate in the survey independently due to serious illness, cognitive impairment (such as dementia or delusions) or other medical conditions; 2) language communication barriers or lack of capability to cooperate in the interview; 3) family caregivers who required confidentiality of the cancer diagnosis from the patient. All the procedures were approved by the Committee on Human Ethics of Dalian Medical University. All enrolled patients signed the written informed consent.
Trained research staff conducted the interview after the patients had undergone at least three days of clinical treatments. We asked whether they were bothered by each of fourteen physical symptoms over the previous two days in the interview. The face-to-face interviews lasted 40-50 minutes. All the measures were verbally administered to enhance data accuracy and reduce the frequency of missing data. Cancer-related clinical information, i.e. type of cancer, stage at diagnosis, medical treatment, and metastatic status, were extracted from the patients’ medical records.
Measures
Suicidal ideation
The Yale Evaluation of Suicidality scale is a 16-item structured questionnaire that assesses current suicidal thoughts and actions, history of suicide attempts, and feelings/attitudes on suicide[35]. It has demonstrated adequate validity in cancer patients [3,35] (see Additional file 1). The first four items in the questionnaire compose a screening measure that assesses the strength of the patients’ wish to live and wish to die (passive SI), the existence of thoughts of killing himself/herself (active SI), and the weighing of dying over living. Because of the rarity with which any suicidality was endorsed, all four screening items were used to assess SI in this study (Cronbach'sα=0.93). Aiming to detect both clear and potential suicidal thoughts, we dichotomized the patients’ scores, where a positive screen (endorsement of any of the four items) =1 and a negative screen = 0.
Independent variables and covariates
Physical symptoms were measured with one item from the McGill Quality of Life Questionnaire (MQOL)[36]. Participants were asked whether they were bothered by each of 14 symptoms over the previous two days with a response of yes and no. Fourteen items were included: pain, shortness of breath, insomnia, weakness, fatigue, nausea, lack of appetite, constipation, diarrhea, edema, cough, vomiting, fever, and bloating.
Health self-efficacy
We measured health self-efficacy by using the Chinese version of the Strategies Used by People to Promote Health (SUPPH)[37], a 29-item validated scale including three dimensions. Each item is rated on a five-point scale ranging from “little confidence” =1 to “quite a lot of confidence” =5. All the items were summed into a score with a higher score indicating a higher sense of health self-efficacy. To evaluate the relative risk of SI, the scores were categorized into high (≥50) and low groups (<50) by the median. The Cronbach's α of the present data was 0.96.
Depression
Clinical diagnosis of depression was evaluated by the 17-item version of the Hamilton Depression Rating Scale (HDRS-17) that assesses the severity of depression symptoms over the past week [38]. It contains 17 items to detect depressive disorders and identifies the severity classification by semi-structured interview. A higher total score indicates a greater severity of depression. Severity classifications are defined as follows: 0–7 for no depression, 8–16 for mild depression, 17–23 for moderate depression, and ≥24 for severe depression. According to the proposal by Zimmerman et al[39], we used the cut-off value of 8 to identify depressive disorders, which showed satisfying reliability (Cronbach’s α=0.84; Split reliability=0.79).
Other variables
Socio-demographic characteristics included sex, age, marital status, education, residence, employment status, household income, smoking, and drinking. Cancer-related clinical variables included cancer type, stage at diagnosis, medical treatment, time since diagnosis, and metastasis status.
Statistical analysis
Descriptive analyses and chi-square were used to compare the socio-demographics and clinical variables between the cancer patients with and without SI. Multivariate logistic regression was conducted to determine the associations between physical symptoms and SI with three models.
We also tested the interaction of health self-efficacy and each physical symptom on SI using multivariate regression analysis. The ratios were adjusted for potential confounding factors to SI, which included socio-demographics, clinical characteristics, and diagnosed depression. All statistical analyses were performed by using IBM SPSS version 21.0. The reported CIs were calculated at the 95% and the statistical significance was set at 0.05 level. All tests were two-sided.