Design
This study uses with methodological cross- sectional design. The aim of this study was to translate and evaluate the psychometric properties and the feasibility of a Persian version of the “11 items De Jong Gierveld Loneliness Scale”.
For performing this study, we selected our samples among older adult people of Tehran with this inclusion criteria: older adults over 65 years, have the ability to use social networks, have a minimum literacy, have a consent to participate in the study via written consent, and be Iranian and fluent in Persian, and older adults without cognitive and memory problems.
1.1 Measurement
We used two questionnaires including demographic questionnaire and Persian version of De Jong Gierveld Loneliness Scale in this study. The demographic questionnaire was composed of personal information including age, gender, marital status, educational level, economic status, employment status, and number of children. The original Loneliness Scale assessed the status of loneliness. This 11-item scale includes two factors: social loneliness (5 items) and emotional loneliness (6 items). This scale is useful because it examines feeling of loneliness and distinguishes between social and emotional loneliness. The Loneliness Scale uses response options on a 5-point Likert-type scale, where 0=None of the time, and 4=All of the time (23).
1.2 Translation
The process of translation and back translation used in the development of the Persian version of this scale was based on the WHO protocol of forward-backward translation technique (24). First, we obtained the written permission from the developer of the scale “Professor De Jong Gierveld “via e-mail for the process of translation and validation of the questionnaire. Second, we invited two English-Persian translators to translate the Loneliness Scale independently. Third, two Persian translations of the questionnaire were reviewed and evaluated by an expert panel (including some of this paper’s authors (H.SH and M.F) as well as two professional translators) and after reviewing both translations and discussing the differences between them, we created a single Persian version of this questionnaire. Fourth, two English -Persian translators (unlike the first two translators) who had no knowledge of the English version of the questionnaire, back-translated the Persian version back into English. Lastly, an expert panel reviewed the two English back-translations. After the necessary revisions and adjustments, the final English version was sent to De Jong Gierveld for confirmation by email.
1.3 Face validity
Face validity was established using both qualitative and quantitative methods. For the qualitative step, we gave the scale to 10 older adults aged over 65 years and asked them to comment on the appropriateness of the appearance, degree of clarity and ambiguity of the selected words and the rational for the sequence of the items in order to achieve the goals of the scale. These viewpoints were included in the final version. Then the final version was assessed using quantitative face validity by measuring item impact scores. In order to perform this phase of validity, 10 target population members were asked to rate items on a five-point scale; where 5= quite important, 4 = somewhat important, 3=medium important, 2= slightly important, and 1=not at all important. An impact score greater than 1.5 is considered appropriate. The impact score was calculated using the following formula: (Impact score=frequency (%) importance) (25).
1.4 Content validity
Both qualitative and quantitative methods were used to calculate content validity. In order to determine the quality of content validity, indicators such as grammar, use of appropriate words and item allocation were evaluated by reviewing the opinions of 10 measurement experts in the fields of measurement, psychology and aging. In addition, to assess the content validity quantitatively, we measured content validity ratios (CVR) and content validity index (CVI) via modified kappa coefficient (K). To calculate CVR, the questionnaire was administered to 10 persons representing education and psychometrics, psychology and aging were asked them to evaluate how essential each items on a three-point scale as follows: 1=Not essential, 2=Useful but not essential, and 3=Essential (26, 27). Then the CVR was evaluated using the following formula: CVR= (ne – [N/2])/(N/2). In this formula, nE is the number of experts who consider an item essential and N is the total number of experts’ panel. Since the number of expert panel was 10, based on Criterion in the Lawshe table, the minimum acceptable CVR is equal to 0.62 (28). Also Items relevancy of the 11-items scale was evaluated by 10 experts on a four-point scale as follows: 1= irrelevant, 2 = somewhat relevant, 3 = quite relevant, 4 = highly relevant. For evaluation CVI, the modified kappa coefficient (K), which is an important complement to CVI, was calculated to determines the degree of chance agreement of experts and eliminate of chance effect for each item was evaluated using the following formula: K = (I-CVI – Pc) / (1 – Pc). Evaluation criteria for Kappa is as follows: good = 0.60–0.74 and the excellent value of Kappa > 0.75. (29).
1.5 Construct validity
Construct validity was evaluated using Exploratory Factor Analysis (EFA) Confirmatory Factor Analysis (CFA) and Convergent and Divergent Validity. Based on this criterion for factor analysis, 10 subjects for each item of scale were needed. Thus, a sample of 200 older adults was considered sufficient for each two stages of EFA and CFA (30). In this study, we used De Jong Gierveld Loneliness Scale with 11 items. We also gathered data via online data gathering. We created the online questionnaire via Google Forms and sent its URL link by email or social networking applications such as a Telegram channel or WhatsApp for target population. Then Data were extracted from Google Form in the Excel file and prepared for analysis.
1.5.1 Exploratory Factor Analysis
EFA was performed with Maximum Likelihood Exploratory Factor Analysis (MLEFA) with varimax rotation. The quality of response and quality of samples was calculated with Kaiser-Meyer-Olkin (KMO) and Bartlett test, where acceptable values for KMO index are greater than 0.7. Furthermore, 95% confidence intervals (CIs) were estimated for each eigenvalue based on CI 95 width (z:1⋅96). Also Horn’s parallel analysis approach was used to determine the number of latent factors that items with communalities <0.2 were excluded from EFA (31). The number of extracted factors was determined based on tree modern approach: a) Exploratory Graph Analysis (EGA), b) parallel analysis, and c) Parallel Analysis Scree Plot (32). Items with factor loading values of 0.3 or greater were considered appropriate. Based on the three-indicator rules, at least three items must exist for each factor and the presence of a single item in the factor was estimated approximately 0.3 based on the formula CV= 5⋅152 ÷ √(n − 2), (in this formula, the ‘CV’ is the number of extractable factors and ‘n’ is the sample size) (33).
1.5.2 Confirmatory Factor Analysis
For this step the structure obtained through EFA was investigated by CFA. The most important objective of CFA is to determine the power of a predefined factor model, which in the present study was the same structure as obtained by EFA, with a set of observed data (34). In CFA, the model fitness was assessed according to the Parsimonious Normed Fit Index (PNFI), Parsimonious Comparative Fit Index (PCFI) and Adjusted Goodness of Fit Index (AGFI) (>0⋅5), Comparative of Fit Index (CFI) and Incremental Fit Index (IFI) (>0⋅9), Root Mean Square Error of Approximation (RMSEA) (>0⋅08), and Minimum Discrepancy Function divided by Degrees of Freedom (CMIN/DF) (<3) (35).
1.5.3 Convergent and divergent validity assessment
CFA is a multimethod-multi-trait approach suitable for construct validity that covers convergent and divergent validity. In order to determine convergent and divergent validity, the correlation between variables was determined using AMOS software and then the weighted standardized regression table was determined. Finally, using Gaskin's coded Excel software, convergent and divergent validity was obtained (36). Convergent and divergent construct validity of the concept of loneliness was measured by the Fornell and Larker approach based on the following parameters: The Average Variance Extracted (AVE) and Maximum Shared Squared Variance (MSV). For convergent validity, the AVE should be greater than 0.5, and for the divergent validity, the MSV must be less than AVE (37).
1.6 Reliability assessment
Reliability is actually the stability and repeatability of a tool. In this study, internal consistency was estimated using the Cronbach's alpha (α), McDonald's omega (Ω), and Average inter-item Correlation (AIC). Coefficients Ω and α values greater than 0.7 were acceptable (38). The AIC value between 0.2 and 0.4 indicated good internal consistency (30). The composite reliability (CR), which replaces Cronbach's alpha coefficient in structural equation modeling were evaluated. the CR values greater than 0.7 were considered acceptable (39).
1.7. Multivariate normality and outliers
Univariate distributions were examined for outliers, skewness, and kurtosis. Multivariate distributions were evaluated for normality and multivariate outliers. Multivariate normality can be assessed through the use of the Mardia's coefficient of multivariate kurtosis. One indication of deviation from a normal distribution is a Mardia's coefficient greater than 8 (40). Multivariate outliers were evaluated through the evaluation of a Mahalanobis distance. Items with a Mahalanobis distance of p < .001 were considered to be multivariate outliers (40). In this study all of the statistical analysis were performed by SPSS26, SPSS-R menu2, AMOS24 and JASP0.14.0.0 software.
Ethics statement
Ethical approval of this study was obtained from the Ethics Committee of Mazandaran University of Medical Sciences (Code: IR.MAZUMS.REC.1399.6682), Sari, Iran.