Translate this page into:
Psychometric properties of the Life Satisfaction Index version A (LSIA) among older adults in Iran
Correspondence to MOHAMMAD TAGHI BADELEH SHAMUSHAKI: Badeleh@gmail.com
[To cite: Chehrehgosha M, Eskandari N, Pahlavanzadeh B, Badeleh Shamushaki M. Psychometric properties of the Life Satisfaction Index version A (LSIA) among older adults in Iran. Natl Med J India 2025;38:326-31. DOI: 10.25259/NMJI_988_2022]
Abstract
Background
One of the most important indicators of mental health in old age is life satisfaction. We aimed at verifying the psychometric properties of the Life Satisfaction Index-A (LSIA), used to evaluate life satisfaction and well-being, among older Iranians.
Methods
The forward–backward procedure was used for translating the English version of the LSIA into Persian. Thereafter, face and content validity were done by 15 specialists. Confirmatory factor analysis (CFA) was done for construct validity. Reliability was evaluated by using the Cronbach’s alpha method. Statistical analysis was performed using Mplus 7.4. p<0.05 was considered statistically significant.
Results
In the face validity, more than 90% of all questions had an impact score above 1.5, content validity ratio (CVR) >0.6, and content validity index (CVI) >0.8. CFA showed that the first-level factors ‘resolution and fortitude’, ‘Zest’ and ‘congruence between desired and achieved goals in life’ explain the first factor of the second level which is ‘the perception of reality’, and the first level factors ‘positive self-concept’ and ‘mood tone’ explain the second factor of the second level which is ‘mental perception’. The proposed structural model showed acceptable to the data and Cronbach’s alpha for the LSIA’s dimensions ranged between 0.89 and 0.95.
Conclusion
The findings suggest that the LSIA appears to be an appropriate instrument for older adults in Iran, but it needs further validation to explore different sub-cultural aspects in the older Iranian population.
INTRODUCTION
The increasing number of the elderly population deserves to live with dignity.1 This population has an opportunity to live longer. However, maintaining the quality of life over these long years and measuring their mental perception, is a major concern for gerontology researchers.2 In general, life satisfaction (LS) is a structure of mental well-being that deals with how people assess the quality of some dimensions of their lives, such as marriage, health, leisure, religion, as well as the quality of happiness, mood, and desire for life.3
Everyone understands and experiences their life differently from other people because everyone has their own social relations, health, economic status, etc. Additionally, people’s perceptions may change over time. Many studies have focused on the concept of LS over the years4–6 because it is one of the most widely used measures of subjective well-being. In addition, it is related to other important concepts such as physical and mental health and quality of life.7–10
LS is a broad concept and is measured using a variety of instruments. Several scales measure LS, but there is no consensus on using a standard tool.11 The Satisfaction with Life Scale (SWLS) can assess and weigh different dimensions of LS but does not assess satisfaction in specific areas of life, such as health or finance.12
The Life Satisfaction Scale (LSS), which assesses the status of health, social factors, and inter-personal relationships, as well as their associations is another such scale. The cultural aspect of each society may influence some dimensions of LSS.2
The Life Satisfaction Index (LSI), which covers general feelings of well-being, negative and positive attitudes about life. The LSI version A (LSIA) is particularly attractive because it is concise, can be implemented and scored quickly, and has acceptable validity and reliability.13 LSIA has been used in various studies and settings, and it seems a good instrument for researchers.13–16
LS is interpreted differently in different cultures, and some socioeconomic factors influence the perception of older adults about their life; thus, it is important to use a suitable instrument for each culture.17
Despite the importance of the concept of LS in older adults, the LSIA has not been validated in the Persian language; therefore, we translated the original LSIA version into Persian to evaluate the psychometric properties of the Persian version of this scale in older Iranian adults.
METHODS
Participants and procedure
For this cross-sectional study, 376 participants were selected by stratified random sampling from among older adults living in 22 cities of Mazandaran Province, Iran. The participants were more than 65 years old, able to read and write, and did not report psychological problems, cognitive impairment, or sensory loss. Based on Munro’s Guideline, between 3 and 10 participants are required for each item for factor analysis (FA).18
After explanation of the aim of the study, the participants signed the consent form, and filled their socio-demographic information (age, sex, education, marital status). Subsequently, the participants completed the LSIA questions with the help of the researcher.
Translation process
The translation into the Persian language was done based on the International Quality of Life Assessment (IQOLA) project guidelines.19 LSIA was translated into Persian by two native Persian translators in accordance with the IQOLA protocol. Two versions of Persian translation were evaluated by another Persian translator and clarified; conceptual equality and acceptability of the items were modified in the translation process. At this stage, to assess the translation process, the researcher in charge held meetings with two native Persian translators who translated the phrases or concepts based on the IQOLA protocol. Inappropriate phrases were identified and rewritten, and any discrepancies between the original version and the translated one were checked. Furthermore, another translator evaluated the two versions of the Persian translation; therefore, the differences and inconsis-tencies between them could be corrected. Finally, the last version of the translated tool was obtained from the integration of the initial translations. In the next step, the last version of the translated tool (from the previous step) was translated from Persian into English by an independent bilingual translator who was not involved in the previous stages of the translation process. The English-translated version was reviewed by the principal researcher and the same first group, and the inconsistencies were assessed to approve the final version. The confirmed questionnaire was filled out by the 20 older adults to evaluate any obscure and vague items for the elderly.
Instrument
Life satisfaction scale. The LSIA is a 20-item questionnaire that measures LS. Neugarten et al.12 developed LSIA with five components; these include zest, resolution and fortitude, congruence between desired and achieved goals, positive self-concept, and mood tone. Twelve items have a positive construct, and the responses are disagree: 0; don’t know: 1; and agree: 2. Eight items have a negative construct, and the ‘agree’ response was equivalent to the zero score. It was assumed that the higher score was associated with higher life satisfaction. Neugarten et al. reported a mean (SD) score of 12.4 (4.4) for the LSIA.12
Psychometric validation
Face validity. Both qualitative and quantitative approaches were used for this study. Qualitative face validity was evaluated by the opinions of 10 older people. The researcher interviewed 10 elderly people of the target group (systematic sampling), face-to-face, to check face validity qualitatively. They were asked to express their understanding of the items and provide their suggestions. Difficulty in comprehending the phrases and misunderstanding about the meaning of some expressions was discussed face-to-face, and the necessary corrections were made to the LSIA based on their comments. The older adults in the qualitative section evaluated the importance of each item on a Likert scale (not important to completely important). The frequency of each item (%) multiplied by its importance was calculated for an impact score, and the impact score >1.5 was considered an appropriate item.20
The researcher also interviewed 10 elderly people of the target group face-to-face to check face validity in a qualitative manner and asked them to express their understanding of the items and provide their opinions and suggestions.
Content validity. Content validity ratio (CVR) and content validity index (CVI) were done for the evaluation of quantitative content validity. CVR evaluated whether the items were essential from the viewpoint of the professionals. In this regard, 3 PhD-qualified nurses, 5 gerontology professionals, and 5 psychologists gave their comments about the LSIA items as follows: necessary, beneficial, or unnecessary. All comments were collected, and the CVR was calculated. Based on the experts’ opinion, CVR was computed for each item. According to the Lawshe table, the acceptable score for CVR based on 15 experts’ viewpoints was 0.49.21 Modification was made based on the collected comments from the reviewers, and the LSIA was resubmitted for the reviewers to analyse the LSIA items by focusing on the relativity, simplicity, and clarity of each item based on a 4-point Likert scale. The CVI was calculated for all LSIA items. CVR >0.8 and CVR >0.49 were assumed to be acceptable for the present study.22
Construct validity. We used confirmatory factor analysis (CFA) to assess the fit of factor structure models of Neugarten et al.12 Because the factor indicators were Likert-type items, and they were ordinal rather than continuous, we based the CFAs on the polychoric correlations of the items. Therefore, we used robust weighted least squares (WLSMV) estimation, which has been shown to perform well for this type of data. Model fit was assessed using the Tucker–Lewis index (TLI), the comparative fit index (CFI), and the root mean square error of approximation (RMSEA). In the current study, TLI and CFI values >0.9 indicated acceptable fit, while values >0.95 reflected excellent fit to the data. For the RMSEA, the values below 0.08 were considered acceptable, while the values under 0.06 were preferred, indicating a close fit to the data.23 The reliability of the measure was assessed by calculating Cronbach’s alpha for each subscale. Statistical analysis was done using Mplus 7.4 at an α=0.05 significance level.
Reliability. The internal consistency was calculated for test reliability. Cronbach’s alpha coefficients >0.7 considered as acceptable reliability.24
RESULTS
In our study, 255 (67.1%) participants were women, 261 (68.7%) were in the age group of 60–69 years, 255 (67.1%) were married, and 306 (80.5%) had a high school education. The highest mean score was for ‘Congruence between desired and achieved goals in life’ domain with 10.40 (1.79), and the lowest mean score was for ‘positive self-concept’ dimension 5.86 (1.44).
Psychometric properties
Face validity. In face validity, the ‘impact score’ was calculated, and the results indicated an agreement above 90% and an impact score above 1.5, which suggests that the items had good face validity and were easily understood by the sample group.
Content validity. According to the participants’ viewpoint, some items needed to be reviewed and corrected. In our study, all items had a CVR >0.6 and CVI >0.8. The means of CVR and CVI for the whole questionnaire were 0.73 and 0.90 (Table 1).
| Question | Disagree | No idea | Agree | CVI | CVR |
|---|---|---|---|---|---|
| 1. As I grow older, things seem better than I thought they would be | 172 (45.7) | 79 (21) | 125 (33.2) | 0.93 | 0.6 |
| 2. I have gotten more of the breaks in life than most of the people I know | 116 (31) | 85 (22.7) | 173 (46.3) | 1 | 0.73 |
| 3. This is the dreariest time of my life | 159 (42.4) | 152 (40.5) | 64 (17.1) | 0.86 | 0.6 |
| 4. I am just as happy as when I was younger | 186 (49.6) | 65 (17.3) | 124 (33.1) | 1 | 0.86 |
| 5. My life could be happier than it is now | 70 (18.7) | 238 (63.6) | 66 (17.6) | 0.8 | 0.6 |
| 6. These are the best years of my life | 161 (42.9) | 94 (25.1) | 120 (32) | 1 | 1 |
| 7. Most of the things I do are boring or monotonous | 114 (30.5) | 187 (50) | 73 (19.5) | 1 | 0.73 |
| 8. I expect some interesting and pleasant things to happen to me in the future | 71 (19.1) | 77 (20.7) | 224 (60.2) | 0.86 | 0.6 |
| 9. The things I do are as interesting to me as they ever were | 116 (30.9) | 103 (27.4) | 157 (41.8) | 0.93 | 0.73 |
| 10. I feel old and sometimes tired | 75 (20.1) | 254 (68.1) | 44 (11.8) | 0.8 | 0.6 |
| 11. I feel my age, but it does not bother me | 115 (30.8) | 46 (12.3) | 212 (56.8) | 0.93 | 1 |
| 12. As I look on my life, I am fairly well satisfied | 106 (28.2) | 56 (14.9) | 214 (56.9) | 1 | 1 |
| 13. I would not change my past life even if I could | 162 (43.3) | 80 (21.4) | 132 (35.3) | 0.8 | 0.6 |
| 14. Compared to other people my age, I’ve made a lot of foolish decisions in my life | 141 (37.5) | 116 (30.9) | 119 (31.6) | 0.8 | 0.6 |
| 15. Compared to other people my age, I make a good appearance | 80 (22.1) | 109 (30.1) | 173 (47.8) | 0.8 | 0.6 |
| 16. I have made plans for things I’ll be doing a month or a year from now | 105 (28.5) | 114 (31) | 149 (40.5) | 0.86 | 0.73 |
| 17. When I think back over my life, I didn’t get most of the important things I wanted | 88 (23.9) | 203 (55.2) | 77 (20.9) | 0.93 | 0.73 |
| 18. Compared to other people, I get down in the dumps too often | 143 (38.9) | 136 (37) | 89 (24.2) | 1 | 0.86 |
| 19. I have gotten pretty much what I expected out of life | 165 (44.7) | 82 (22.2) | 122 (33.1) | 1 | 0.86 |
| 20. In spite of what people say, the lot of the average man is getting worse | 114 (31.1) | 114 (31.1) | 139 (37.9) | 0.8 | 0.6 |
Reliability. The Cronbach’s alpha for the LSIA’s dimensions ranged between 0.89 and 0.95 (Table 2).
| Factor | Mean (SD) | Cronbach’s alpha | ||
|---|---|---|---|---|
| First order factors | Second order factors | First order factors | Second order factors | |
| Zest | 8.25 (1.48) | 28.46 (3.55) | 0.94 | 0.97 |
| Resolution and fortitude | 9.79 (1.89) | – | 0.89 | – |
| Congruence between desired and achieved goals in life | 10.40 (1.79) | – | 0.94 | – |
| Positive self-concept | 5.86 (1.44) | 11.87 (1.97) | 0.88 | 0.96 |
| Mood tone | 6.03 (1.16) | – | 0.97 | – |
CFA. The results showed that a ve-factor solution of the LSIA did not exhibit an acceptable t to the data. In further analysis, a significant correlation was observed between ‘Zest’, ‘resolution and fortitude’, and ‘Congruence between desired’ and achieved goals in life. In addition, a significant correlation was observed between ‘positive self-concept’ and ‘mood tone’; therefore, the existence of potential multicollinearity was examined. There was no sign of multicollinearity between the dimensions.
To consider the correlations between dimensions, the second-order structure was used. Accordingly, the first level factors ‘resolution and fortitude’, ‘Zest’ and ‘Congruence between desired and achieved goals in life’ explain the first factor of the second level, i.e. the perception of reality. The first level factors ‘positive self-concept’ and ‘mood tone’ explain the second factor of the second level, i.e. mental perception. The goodness-of-fit indices of this model showed that although the chi-square test was significant (p<0.001), CFI (0.971) and TLI (0.967) showed excellent and RMSEA (0.078, 95% CI: 0.071, 0.86) showed an acceptable fit of data to the proposed model (Fig. 1).
- Confirmatory factor analysis model for the Life Satisfaction Index version A χ2=545.08, p<0.001, comparative fit index=0.971, Tucker–Lewis index=0.967, root mean square error of approximation=0.078 CBD and ALG congruence between desired and achieved goals in life
DISCUSSION
We aimed to assess a valid and reliable instrument that could be used for older adults in Iran. Many studies have been done to measure LS with different tools, but there is still no consensus on the use of a standard tool. Our study shows that the LSIA is a multidimensional scale and has acceptable psychometric properties. We used the CFA method to confirm this scale. The CFA can evaluate the goodness of fit indices in accordance with the factor structure of the scale, which can provide a more accurate and conclusive assessment of the hidden factors.
The results of content validity showed that the items of the LSIA were understandable by older adults in Iran. The CVI and CVR scores were in an acceptable range. These results indicate that the LSIA is a suitable instrument to assess LS. In line with our results, Franchignoni et al. reported satisfactory internal consistency of the scale.25
In a systematic review, Powell et al., reported LSIA to have a satisfactory score in content validity in relevance, comprehensiveness, and comprehensibility.26
Tagharrobi et al., did a psychometric evaluation of the Life Satisfaction Index-Z (LSI-Z) in older adults in Iran, and found the internal consistency to be 0.78–0.79.27 Elmståhl et al. reported high internal consistency for the LSIA.28
Assessment of abstract components is difficult, especially in the elderly population. Hence, the fluency and simplicity of each question is important. In the second step, the goal was to incorporate the viewpoints of all experts involved with the elderly community to evaluating the questions of this instrument. All questions that needed to be reconsidered were edited and reconsidered by experts. Therefore, by researchers being sensitive to the correct meaning of each question, acceptable results can be obtained for face and content validity.
We used the CFA for the evaluation of construct validity. The CFA can evaluate the goodness-of-fit of the results in accordance with the factor structure of the scale. Our data analysis confirmed that the final model was suitable for the investigation of LS in older adults. The CFI, TLI, and RMSEA were used as goodness-of-fit indices. The results showed the final model based on CFA had an acceptable goodness-of-fit. In the study of Franchignoni et al., EFA was done for the psychometric assessment of LSIA, and the results indicated that the Italian version of LSIA had cultural equivalence with the English LSIA, and LSIA was a suitable instrument from a psychometric standpoint.25 In the study of Tagharrobi et al., construct validity was assessed using the known-groups comparison method and found that the scores obtained from the questionnaire indicated that the LSI-Z is a valid tool.27
Neugarten et al., the LSIA scale developer, assumed 12 positive and 8 negative items for 5 dimensions of the LSIA scale—Zest, Resolution and fortitude, Congruence between desire, Positive self-concept, and Mood tone.12 Liang et al. explored the dimensions of the LSIA, and reported that LSIA had one second-order factor and three first-order factors, and 11 items loading on first-order factors.29 They stated that although the extracted model was conducted on those over 65 years old, the role of variables such as age, gender, and race were not considered in the final model. These factors may change the proposed model or uncover possible variations in the final model; therefore, they suggested being careful in generalizing and interpreting the results when using LSIA according to the studied population.
Shmotkin et al. explored the structure of the LSIA in older adults in Israel. Their results confirmed that the LSIA has one second-order factor and a three-factor first-order structure (20 loaded items). The results of their analysis revealed that Zest has two alternate forms that are called Zest-Via-Time (by growing old, the potentialities of time might be decreased while the remaining time is valuable) and Zest-Via-Interest (feeling good about the surrounding atmosphere without having a negative sense). It seems that the two concepts of Zest can be considered in the two different models, although they may overlap with each other.14 Shmotkin et al. validated the LSIA in community-dwelling older adults in Israel without consideration of any heterogeneity variants in the study population. Never-theless, due to the subjective nature of this component (LS), they stated that there is a need for further research with a more accurate assessment of the elderly population.14
In a Swedish National study, Fagerström et al. reported that the three-factors, mood, zest and congruence, had an acceptable fit to the data. They considered the effect of age, functional ability, and depression. They believed that evaluation of the psychometric properties of LSIA without taking into account the influencing factors, such as age and comorbid conditions, can lead to a different arrangement of loading of the first or second-order factors in LSIA.30 They also measured the effect of time on LSIA structure and mentioned that the final construct of LSIA had not changed over 6 years. They emphasized that none of the previous studies had examined the interaction of time and LSIA. Accordingly, time may change the final model in different populations.
The results of various studies show that regardless of the development of the 5-dimensional model by Neugarten et al. in the validation of this tool in different years and in different populations12, the concepts of the questionnaire have changed, and even the number of items has decreased. As the results of Fagerström et al.30 study in 2012 show, in validating the LSIA in the elderly population, we must pay attention to the heterogeneity of the population because it can change the structure and arrangement of items in the questionnaire.
Hoyt and Creech believed that for the evaluation of LS, it was better to use groups with homogeneous characteristics.31 In other words, researchers should test the factorial validity of LSIA and check the homogeneity in subgroups before interpreting the information about LS.
It is also noteworthy that recent models extracted in different studies were done based on the limited number of LSIA models that were taken from previous studies. Thus, it can be said that there may be different models of LSIA that researchers have not yet tested, and some of them may have different models.30
In our study, unlike other studies, the concepts have been defined in two second-order factors, which are not consistent with the studies that have been published in this field. Each dimension of LSIA may be related, in a distinct way, to certain independent variables. Perhaps, in evaluating the concept of LS, careful attention should also be paid to its predictive variables such as heterogeneity of the older population.
Considering different types of heterogeneity, it seems that conducting more studies in the field of LSIA in different cultures and ethnicities can clarify more dimensions of this instrument. Thus it can improve the precise assessment of LS in the older population.
Unfortunately, not many studies have been done to validate the LSI for the elderly, but the results of our study, as well as the mentioned studies, show that this instrument has the ability to assess LS properly in the elderly. The instruments developed for LS are a concept that has been formed from a western perspective and with an individualistic approach. Since the standards for judging LS are different across cultures, modern researchers consider LS in the context of different cultural aspects in different countries.32,33
Importantly, any instrument that is to be implemented from the primary society in another society must first be adapted to the culture of the target society. Hence, psychometric studies of LS instruments must be conducted in different cultures in order to have a precise assessment of LS in the elderly.34 Given that the LSIA is a potentially useful scale for the elderly, it needs further research to be validated in order to use it in any culture.
Limitations
We did not do test–retest reliability convergent, and divergent validity. These could be considered for future studies.
Conclusion
Our findings suggest that the LSIA is an appropriate instrument in older adults in Iran and can be considered a useful scale for conducting research. Based on the findings of our study, the LSIA is easy to use and comprehensible for older adults. The LSIA is suitable for the evaluation of health and social care domains in older people. However, it needs more studies exploring different sub-cultural aspects in the older Iranian population.
Conflicts of interest
None declared
References
- Analysis of life satisfaction of the elderly population on the example of Sweden, Austria and Germany. Popul Econ. 2019;3:102-16.
- [CrossRef] [Google Scholar]
- The Persian Version of the “Life Satisfaction Scale”: Construct Validity and Test-Re-Test Reliability among Iranian Older Adults. J Cross Cult Gerontol. 2018;33:121-34.
- [CrossRef] [PubMed] [Google Scholar]
- Factors associated with life satisfaction in older adults with chronic pain (PainS65+) J Pain Res. 2020;13:475-89.
- [CrossRef] [PubMed] [Google Scholar]
- The psychometric properties of the Turkish version of the Riverside Life Satisfaction Scale-Adult Form. SAGE Open. 2020;10:215824402097982.
- [CrossRef] [Google Scholar]
- Predictors of life satisfaction among multicultural African families in South Korea. J Psychol Afr. 2019;29:7-12.
- [CrossRef] [Google Scholar]
- Immigrant life satisfaction in Europe: The role of social and symbolic boundaries. J Ethn Migr Stud. 2019;45:1027-50.
- [CrossRef] [Google Scholar]
- What matters, and what matters most, for change in life satisfaction in the oldest-old? A study over 6 years among individuals 80+. Aging Ment Heal. 2009;13:191-201.
- [CrossRef] [PubMed] [Google Scholar]
- Psychological and physical dimensions explaining life satisfaction among the elderly: A structural model examination. Arch Gerontol Geriatr. 2009;48:291-5.
- [CrossRef] [PubMed] [Google Scholar]
- Life satisfaction and mortality in elderly people: The Kangwha Cohort study. BMC Public Health. 2012;12:54.
- [CrossRef] [PubMed] [Google Scholar]
- Personality, culture, and subjective well-being: Emotional and cognitive evaluations of life. Annu Rev Psychol. 2003;54:403-25.
- [CrossRef] [PubMed] [Google Scholar]
- The satisfaction with life scale: Psychometric properties in Pakistani population. Med J Islam Repub Iran. 2020;34:1-6.
- [CrossRef] [PubMed] [Google Scholar]
- The measurement of life satisfaction. J Gerontol. 1961;16:134-43.
- [CrossRef] [PubMed] [Google Scholar]
- The reliability and validity of the life satisfaction index-A with survivors of traumatic brain injury. Brain Inj. 2004;18:1127-34.
- [CrossRef] [PubMed] [Google Scholar]
- The structure of the Life Satisfaction Index A in elderly Israeli adults. Int J Aging Hum Dev. 1991;33:131-50.
- [CrossRef] [PubMed] [Google Scholar]
- Evaluation of life satisfaction index of the elderly people living in nursing homes. Arch Gerontol Geriatr. 2005;41:23-9.
- [CrossRef] [PubMed] [Google Scholar]
- Life satisfaction index among elderly people residing in Gorgan and its correlation with certain demographic factors in 2013. Glob J Health Sci. 2015;8:41.
- [CrossRef] [PubMed] [Google Scholar]
- A cross-cultural comparison of the dimensions of child and adolescent life satisfaction reports. Soc Indic Res. 2004;66:61-79.
- [CrossRef] [Google Scholar]
- Psychometric properties of the King Spiritual Intelligence Questionnaire (KSIQ) in physical veterans of Iran-Iraq warfare. J Mil Med. 2015;17:145-53.
- [Google Scholar]
- Methods for validating and norming translations of health status questionnaires: The IQOLA project approach. J Clin Epidemiol. 1998;51:953-9.
- [CrossRef] [PubMed] [Google Scholar]
- Health-related quality of life in obstructive sleep apnoea. Eur Respir J. 2002;19:499-503.
- [CrossRef] [PubMed] [Google Scholar]
- A quantitative approach to content validity. Pers Psychol. 1975;28:563-75.
- [CrossRef] [Google Scholar]
- A nurses' alarm fatigue questionnaire: Development and psychometric properties. J Clin Monit Comput. 2017;31:1305-12.
- [CrossRef] [PubMed] [Google Scholar]
- Structural equation modeling in medical research: A primer. BMC Res Notes. 2010;3:1-10.
- [CrossRef] [PubMed] [Google Scholar]
- The Polycystic Ovary Syndrome Health-Related Quality of Life Questionnaire (PCOSQ): A validation. Hum Reprod. 2004;19:371-7.
- [CrossRef] [PubMed] [Google Scholar]
- Life satisfaction index: Italian version and validation of a short form. Am J Phys Med Rehabil. 1999;78:509-15.
- [CrossRef] [PubMed] [Google Scholar]
- Measuring quality of life in Duchenne muscular dystrophy: A systematic review of the content and structural validity of commonly used instruments. Health Qual Life Outcomes. 2020;18:263.
- [CrossRef] [PubMed] [Google Scholar]
- Psychometric evaluation of the Life Satisfaction Index-Z (LSI-Z) in an Iranian elderly sample. Payesh. 2011;10:5-13.
- [Google Scholar]
- The life satisfaction index-A (LSI-A): Normative data for a general Swedish population aged 60 to 93 years. Clin Interv Aging. 2020;15:2031-9.
- [CrossRef] [PubMed] [Google Scholar]
- Dimensions of the Life Satisfaction Index A: A structural formulation. J Gerontol. 1984;39:613-22.
- [CrossRef] [PubMed] [Google Scholar]
- Factorial validity and invariance of the Life Satisfaction Index in older people across groups and time. Arch Gerontol Geriatr. 2012;55:349-56.
- [CrossRef] [PubMed] [Google Scholar]
- The Life Satisfaction Index: A methodological and theoretical critique. J Gerontol. 1983;38:111-16.
- [CrossRef] [PubMed] [Google Scholar]
- The measurement of subjective wellbeing: Item-order effects in the Personal Wellbeing Index-Adult. J Happiness Stud. 2018;19:315-32.
- [CrossRef] [Google Scholar]
- Indicators of subjective well-being as characteristics for typology building. Socio Studies. 2016;10:21-32.
- [Google Scholar]
- Review of the Satisfaction With Life Scale In: Diener E, ed. Assessing well-being. Social Indicators Research Series. Vol 39. Dordrecht: Springer; 2009. p. :99-118.
- [CrossRef] [PubMed] [Google Scholar]