Quality of Life in Alzheimer’s Disease (QoL-AD) Scale: Factor Solutions in Non-Demented Elders

1. Quality of Life in Alzheimer’s Disease (QoL-AD) Scale: Factor Solutions in Non-Demented Elders Andrew J. Revell, Grace I. L. Caskie, Sherry L. Willis, & K. Warner Schaie The Pennsylvania State University

2. Acknowledgments This research was supported by a grant from the National Institute on Aging (R37 AG08055) to K. Warner Schaie and by a National Institute on Mental Health training grant, Training in Research and Mental Health and Aging (MH18904). We gratefully acknowledge the enthusiastic cooperation of the members and staff of the Group Health Cooperative of Puget Sound.

3. Introduction • The QoL-AD was created to assess perceived quality of life by individuals with AD. At the time of initial development little research had been published in this area. Given research by Lawton (1983, 1991) and others, there was a need to develop measures suitable for reliable study of decline in quality of life. • The QoL-AD was designed to tap domains such as functional status, psychological well-being, physical health, and relationships with others. • The measure has been evaluated for reliability and validity and related to other self-report measures, but there has been no investigation of its factor structure.

4. Objectives • To explore the factor structure of the QoL-AD with a larger sample of non-demented older adults. • To conduct a confirmatory factor analysis with the sample to identify the most suitable solution. • To test the invariance of the obtained factor structure with respect to age and gender groups.

5. Sample • Community-dwelling older adults (N=499, F=288, M=211), aged 57-95 (M=73.07, SD=8.30) from the Seattle Longitudinal Study (SLS). Years of education: 7-20 years (M=15.05, SD=2.77). • All participants had completed a series of neuropsychological assessments between 1997-2000, including the Quality of Life in Alzheimer’s Disease Scale.

6. Quality of Life in Alzheimer’s Disease Scale (QoL-AD; Logsdon, Gibbons, McCurry, & Teri, 1999) • A 13-item, self-report measure of current overall quality of life. These are unweighted. - Sample item from the original, unweighted, 13-item scale Current Situation Poor Fair Good Excellent Item: 3. Mood Response: □ □ □ □ Scoring: 1 2 3 4 • A 26-item extended version is also available with the same 13 current items which are weighted by multiplying each by an importance rating - Sample item from the extended, weighted, 26-item scale ImportanceCurrent Situation Very Somewhat Not Poor Fair Good Excellent Response: □ □ □ 3. Mood □ □ □ □ Scoring: 2 1 0 1 2 3 4 - The score on Importance is multiplied by the score on Current to produce a weighted score, ranging from 0 to 8, for each of the 13 items

7. Exploratory Factor Analyses • Exploratory factor analysis was conducted for the total sample using principal axis factoring of QoL-AD item-level data with Promax rotation. • Given previous exploratory factor analysis with a smaller subset of this sample, both a two and three-factor solution appeared possible. Two and three factor solutions were therefore explored for both weighted and unweighted scores.

8. Two-Factor: Exploratory Factor Analysis • The two factor solution without weighting indicated a relatively simple structure with standardized regression coefficients ranging from .36 - .78 on Factor 1 and from .35 - .66 on Factor 2. 1- Factor 1 (Well-being) included items on: physical health, energy, self, ability to do chores around the house, ability to do things for fun, and life as a whole 2- Factor 2 (Relationships) included items on: mood, living situation, family, marriage, friends, self, money, and life as a whole - The item on memory did not meet the criterion .salient loading of .3 or higher. Two items split between the two factors: self and life as a whole. • The two factor solution with weighting indicated a simple structure with standardized regression coefficients ranging from .38 - .77 for Factor 1 and from .30 to .59 for Factor 2. 1- Factor 1 (Well-being) included items on: physical health, energy, mood, memory, self, ability to do chores around the house, ability to do things for fun, and life as a whole 2- Factor 2 (Relationships) included items on: living situation, family, marriage, friends, and life as a whole - The item on money did not meet the criterion salient loading of .3 or higher. One item split between the two factors: life as a whole.

9. Three-Factor: Exploratory Factor Analysis • The three factor solution without weighting indicated a simple structure with standardized regression coefficients ranging from .30 - .75 on Factor 1, from .32 - .65 on Factor 2, and from .41 - .53 on Factor 3. 1- Factor 1 (Well-being) included items on: physical health, energy, ability to do chores around the house, ability to do things for fun, and life as a whole 2- Factor 2 (Relationships) included items on: living situation, family, marriage, money, and life as a whole 3- Factor 3 (Awareness of Self & Others) included items on: mood, friends, self - The item on memory did not meet the criterion salient loading of .3 or higher. One item split between two factors: life as a whole. • The three factor solution with weighting indicated a simple structure with standardized regression coefficients ranging from .34 - .78 on Factor 1, from .32 - .48 on Factor 2, and from .32 - .62 on Factor 3. 1- Factor 1 (Well-being) included items on: physical health, energy, self, ability to do chores around the house, ability to do things for fun, and life as a whole 2- Factor 2 (Personal Situation) included items on: mood, living situation, memory, friends, self, money 3- Factor 3 (Relationships) included items on: living situation, family, marriage - Two items split between two factors: living situation and self.

10. Initial Confirmatory Factor Analyses • Confirmatory Factor Analyses of the whole sample on the two and three factor solutions with weighted and unweighted items indicated the best fit for the three factor unweighted solution (see Table 1). • The overall chi square was significant, however the relative fit indices indicated a good fit (RMSEA=0.053; NFI=.994; CFI=.997; RFI=.991). • Therefore, all further analyses utilize the three factor unweighted solution.

11. Factorial Invariance Analyses • Factorial Invariance of the unweighted three factor solution was assessed (see Figure 1). • The three factors (Well-being, Relationships, and Awareness of Self & others) were tested for invariance by age group and gender. 1- Age groups: Young-old (n=270, 57-74 years of age) and Old-old (n=229, 75-95 years of age) 2- Gender groups: Male (n=211) and Female (n=288)

12. Evaluation of Factorial Invariance • Factorial invariance (FI) by groups involves a nested sequence of increasingly stringent models allowing the models to be compared for overall fit. • Three main types of factorial invariance (Meredith, 1993), in addition to the baseline or configural model (Horn, McArdle, & Mason, 1983), are: 1. Weak: Factor loadings are set as equal 2. Strong: Factor loadings and mean intercepts are set as equal 3. Strict: Factor loadings, mean intercepts, and unique variances are set as equal

13. Factorial Invariance Fit Indices • Based on absolute fit statistics (i.e., chi square, difference chi square), weak factorial invariance, was accepted for both age and gender (see Table 2). • Factorial invariance was also supported by the relative fit statistics for a good fit (NFI, CFI, TLI , RMSEA) for both age and gender groups, for the weak model. • Factor correlations between groups are presented in Tables 3-6. Item correlations in comparison to those by the test measure authors are presented in Table 7. • Across all the groups, the items under the Well-being factor had the highest regression estimates, followed by the items under the Relationships factor.

14. Discussion • Previous research by Logsdon, Gibbons, McCurry, and Teri (1999) found that the QoL-AD was a reliable self-report measure when administered to probable AD patients (n=77) and their caregivers. However, no information was available as to the factor structure of the measure, nor had research explored how weighting may affect the structure. • The objective of this study was to investigate the factor structure of the QoL-AD with a larger sample of individuals ages 57 to 95 and assess factorial invariance by age and gender groups. • Following exploratory factor analysis, the two and three factor weighted and unweighted solutions separated the items in different ways. Confirmatory factor analysis identified the three factor unweighted solution as having the best fit. Therefore, the unweighted three factor solution was investigated further for factorial invariance by age and gender groups.

15. Summary • Exploratory Factor Analyses suggested the acceptability both two and three factor solutions swith weighted and unweighted items. The three factor solutions were cleaner than the two factor solutions in terms of simple structure. • Confirmatory factor analysis revealed a better fit, based on absolute and relative fit indices, for the unweighted three factor solution. • Weak factorial invariance was then found for both age and gender groups for the unweighted three factor solution. • Future research might investigate the possibility of a single factor with a higher-order factor model, given the high degree of factor intercorrelation. • The similarity between the authors’ item correlations for Total QoL-AD score and our own suggest a similar pattern of findings across most items.