Materials and Methods
This quantitative, cross-sectional survey was conducted in the Rehabilitation and Physiotherapy Department of Tongji Hospital, China among individuals with SCI from July to December 2020. Convenience sampling was used to recruit participants exclusively from Tongji Hospital, and all questionnaires were administered in a written format with checkbox responses. For participants unable to complete the questionnaires independently, three trained researchers provided assistance, while self-administration was encouraged whenever possible. Inclusion criteria required participants to be at least 18 years old, have traumatic or non-traumatic SCI for a duration exceeding 6 months, and reside within the community. Individuals with mental health or cognitive impairments were excluded from the study.

The survey included demographic and injury-related questions, alongside two validated instruments: the WHOQOL-BREF for assessing quality of life and the Satisfaction with Life Scale (SWLS) ( Hao, 2000 ; Diener et al., 1985 ).

The WHOQOL-BREF scale was utilized to assess QoL among individuals with physical disabilities ( Power, Green & Group, 2010 ). Introduced in mainland China in 1998 ( Hao, 2000 ), the Chinese version of the WHOQOL-BREF has demonstrated acceptable reliability, validity, and suitability as a comprehensive generic health-related QoL measure, supporting its use in studies of QoL and disability among Chinese individuals with SCI ( Lin et al., 2007 ; Tian, 2009 ). The initial two items of the Chinese version assess general QoL and overall health. The remaining 24 items are rated on a five-point Likert scale and categorized into four domains: physical health (seven items), psychological well-being (six items), social relationships (three items), and environmental health (eight items). Domain-specific summary scores were calculated and converted to a 0–100 scale, following the manual’s guidelines, where a score of 0 denotes the lowest QoL and 100 signifies the highest QoL ( World Health Organization, 1998 ). In this study, after conducting the initial assessment, the WHOQOL-BREF questionnaire was re-administered to 30 participants after a 2-week interval. The Intraclass Correlation Coefficient (ICC) was then computed to evaluate the reliability of the measurements. The Cronbach’s alpha for the WHOQOL-BREF was found to be 0.82, indicating good internal consistency, while the ICC for the total scale score was 0.95, with subscale ICC values ranging from 0.89 to 0.98, demonstrating excellent reliability.

The Satisfaction with Life Scale (SWLS) is one of the most widely used instruments for measuring subjective well-being ( Diener et al., 1985 ). The SWLS demonstrates validated psychometric properties, including high internal consistency and acceptable test-retest correlations ( López-Ortega, Torres-Castro & Rosas-Carrasco, 2016 ). Developed in 1985, the SWLS was specifically designed to assess subjective well-being across various patient populations, including individuals with spinal cord injuries ( Post et al., 2012 ). The scale comprises five items, each rated on a seven-point Likert scale ( e.g ., Item 1: “In most ways, my life is close to ideal”). All five items are positively keyed, allowing for the calculation of an overall score. Scores range from 5 to 9, indicating “extremely dissatisfied” with life; 20 to 30, signifying a “good” level of satisfaction; and 31 to 35, reflecting “extremely satisfied” respondents, with scores in this range suggesting a high level of life satisfaction ( Pavot & Diener, 2008 ). In this study, we analyzed scores from 223 Chinese participants aged over 18 years and compared them to those of healthy Chinese adults recruited from the general community. Following the initial assessment, the WHOQOL-BREF questionnaire was re-administered to 30 participants after a 2-week interval. The Intraclass Correlation Coefficient (ICC) was calculated to measure reliability. The Cronbach’s alpha for the scale was 0.89, and the ICC for the total scale score was 0.98, indicating excellent reliability.

Data analysis was conducted using SPSS version 23 and R (version 4.0.2, R Foundation for Statistical Computing, Vienna, Austria), reporting descriptive statistics, means, and standard deviations. The data were found to follow a normal distribution, and Student’s independent t-test was computed to explore differences between SCI groups. Additionally, Pearson’s correlation coefficients were calculated to determine associations between the WHOQOL-BREF and the SWLS.

Multiple linear regressions were utilized to identify key determinants of the WHOQOL domain scores, excluding items 1 and 2, with the SWLS score serving as the outcome variable. Variables were selected based on their theoretical or clinical significance, as controls to mitigate confounding effects, and according to their statistical significance. This methodical approach aimed to ensure the robustness of the model by integrating essential clinical insights and statistically reliable relationships.

Cronbach’s alpha was calculated to evaluate the internal consistency of the WHOQOL-BREF questionnaire, while test-retest reliability was assessed through the application of the ICC. All statistical tests were two-tailed, with a significance level set at p < 0.05. The research project was approved by the ethics committees of two affiliated hospitals of Tongji Medical College, with ethical approval granted under number TJ-IRB20210314.