Participants
The 2013 CSLC targeted 295,367 households based on 5,530 randomly selected enumeration districts (EDs) of the 2010 Population Census, and 234,383 households (79.4%) completed the ‘household questionnaire’ and the ‘health questionnaire’ in June-July 2013 [13]. All household members, except for those who did not live at home during the survey period, responded to the questionnaires. The ‘LTC questionnaire’ was distributed (n=7,270) to 2,500 randomly selected EDs from the original 5,530 EDs, and 6,342 questionnaires were collected from households with a member who was officially certified as needing LTC at the time of the survey.
The flowchart showing the process of extracting the data for our quantitative analysis is presented in Figure 1. Among the 6,342 responses to the LTC questionnaire, we identified the nursing care recipients whose main reason for receiving care was dementia (n = 1,042). Based on the household questionnaire, the main CGs for the abovementioned household members were identified, and 683 CRDs with family CGs were extracted. We then excluded CGs who lacked data on age, sex, and psychological distress. The remaining 643 dyads of CRDs and their main CGs were included in the analysis.
This study was approved by the ethics review committee of the National Center of Neurology and Psychiatry (approval number: A2017-001) and it conformed to the provisions of the Declaration of Helsinki, and Japanese Ethical Guidelines for Medical and Health Research Involving Human Subjects. We obtained permission to use certain data from the 2013 CSLC for purposes other than those originally intended by the MHLW according to the Statistics Act, Article 33. Because we did not use any personally identifiable information, the requirement for written informed consent was waived by the Ethics Committee and the Statistics Act since the study involved record review only.
Measures
Kessler’s Psychological Distress scale (K6) was used to measure psychological distress in the CSLC. The K6 scale was developed as a brief screening tool for nonspecific psychological distress in adults and consists of 6 questions asking about psychological symptoms in the previous month [15, 16]. In line with the recommended K6 cutoff point, we defined serious psychological distress according to a K6 score ≥13 [17].
As independent variables of the CRDs, we included data on levels of LTC needs as well as demographics (age, and sex). Regarding the main CGs, we extracted data from the 2013 CSLC on the following variables: age, sex, relationship with the CRD, marital status, educational attainment, having someone to consult with, knowing how to access consulting services, time spent on nursing care (almost all day, other), participation in 16 nursing activities, the presence or absence of subjective symptoms within the last few days, paid work, and regular visit of hospitals. With respect to household factors, we used data concerning the number of family members at home, total household monthly expenditures, the presence or absence of other family members in need of nursing care, and house ownership.
Statistical Analysis
Analyses were conducted using SAS version 9.4 (SAS Institute Inc., Cary, NC, USA). To describe the sociodemographic characteristics of participants stratified by the presence or absence of serious psychological distress, we conducted unpaired Student's t-tests and chi-square tests for continuous variables and categorical variables, respectively. Continuous variables are presented as the means ± SDs.
To examine the association between CGs’ psychological distress (K6 ≥13) and factors related to CRDs, CGs, and households, we conducted multivariable logistic regression analysis using a forward selection method based on the score test (selection criteria: p<0.05). In that analysis, the dependent variable was CGs’ psychological distress, and the independent variables were factors related to the CRDs (age, sex, and level of LTC required), CGs (age, sex, relationship with CRD, marital status, educational attainment, having someone to consult with, knowing how to access consulting services, time spent on nursing care, participation in 16 nursing activities, having subjective symptoms within a few days, and regularly visiting hospitals), and household (number of family members at home, house ownership, total household monthly expenditures, and other family members in need of nursing care). The C statistic and Hosmer-Lemeshow test were employed to evaluate the goodness-of-fit of the estimated logistic model. We considered a value of P < 0.05 to be significant.