Confirmatory Factor Analysis of the Geriatric Depression Scale

Transcription

1 The Gerontologist Vol. 44, No. 6, Copyright 2004 by The Gerontological Society of America Confirmatory Factor Analysis of the Geriatric Depression Scale Kathryn Betts Adams, MSW, PhD, 1 Holly C. Matto, MSW, PhD, 2 and Sara Sanders, MSW, PhD 3 Purpose: The Geriatric Depression Scale (GDS) is widely used in clinical and research settings to screen older adults for depressive symptoms. Although several exploratory factor analytic structures have been proposed for the scale, no independent confirmation has been made available that would enable investigators to confidently identify scores for the subdimensions of depression represented in the scale. Design and Methods: This article describes a confirmatory factor analysis of the 30-item GDS, with the factor structure based on an exploratory principal components analysis that was published earlier. The original study sample consisted of 327 community-dwelling adults aged years. The confirmatory factor analysis was performed on data from an independent sample of 294 adults aged years who resided in retirement facilities. Results: The proposed final measurement model uses 26 of the items from the GDS in five factors and obtains a goodness-of-fit index of.90. The resulting distinct subdimensions are Dysphoric Mood, Withdrawal Apathy Vigor, Hopelessness, Cognitive, and Anxiety. Implications: Although results should be considered preliminary, the use of these five subdimensions as subscales for scoring purposes may improve the precision and utility of the GDS as an assessment tool for older adults in health, mental health, and research contexts. We acknowledge Ms. Erin Auth for her work with data collection and Dr. McKee McClendon of the Case Western Reserve University Memory and Aging Center for his assistance with the tetrachoric transformations. Dr. Matto is now with the School of Social Welfare, University at Albany, State University of New York. Address correspondence to Kathryn Betts Adams, Mandel School of Applied Social Sciences, Case Western Reserve University, Euclid Avenue, Cleveland, OH kathryn.adams@case.edu 1 Mandel School of Applied Social Sciences and University Memory and Aging Center, Case Western Reserve University, Cleveland, OH. 2 School of Social Work, Virginia Commonwealth University, Alexandria. 3 School of Social Work, University of Iowa, Iowa City. Key Words: Assessment tools, Psychometrics, Mental health The Geriatric Depression Scale (GDS; Brink et al., 1982) is an instrument that has been widely used in clinical work and research since its first appearance over 20 years ago. It has the distinction of being the first screening scale for depression that was specifically designed to be used with older adults (Yesavage et al., 1983), in part by eliminating frankly somatic and sexual complaints that appeared on other depression screening scales but are most likely to be affected by advanced age. The GDS has been used to screen for depressive symptoms in a wide range of research studies in a number of health and service settings (Peach, Koob, & Kraus, 2001). It is an indictor of its breadth of application that the public access Web site maintained by the scale s authors currently offers links to translations of the scale in 24 languages (Yesavage, 2003), and a recent review of the reliability of the GDS cites 338 published articles using the scale (Keiffer & Reese, 2002). A number of studies have examined the properties and demonstrated the utility of the GDS with older adults of diverse cultures or nationalities, such as Japanese American, Chinese, and Turkish (e.g., Boey, 2000; Ertan, & Eker, 2000; Iwamasa, Hilliard, & Kost, 1998), although recent review has cautioned that cultural factors may affect the reliability or validity of the GDS (Mui, Burnette, & Chen, 2001; Mui, Kang, Chen, & Domanski, 2003). Some investigators have found that the GDS does not adequately assess depression in persons who have mild to moderate dementia (Montorio & Izal, 1996). Despite some of these concerns, the GDS has been recommended for standard use in research studies with older adults to facilitate cross-comparisons and meta-analyses (Koder, Brodaty, & Anstey, 1996), for standard screening by geriatric social workers (Peach et al., 2001) and for screening in geriatric settings by 818 The Gerontologist

2 Table 1. Summary of Item Assignment to Factors for Published PCAs of the GDS, Listed by Study First Author Item No. Description Parmalee (n ¼ 417) Sheikh (n ¼ 326) Salamero (n ¼ 234) Mitchell (n ¼ 868) Adams (n ¼ 327) 1 Satisfied with life D D Pos D 2 Dropped activities, interests W-A V W W-A-V 3 Your life is empty D D D D 4 Often get bored D Agit D D D 5 Hopeful about the future D Pos D-H 6 Bothered by thoughts Wor D Wor 7 In good spirits D Pos D Pos D 8 Afraid something bad will happen Wor D D Wor 9 Happy most of the time D Pos D Pos D 10 Often feel helpless D D D D D-H 11 Restless and fidgety Anx Agit D Agit 12 Prefer to stay at home W-A W W-A W W-A-V 13 Worry about the future Wor D Wor 14 Problems with memory C C Not C 15 Wonderful to be alive now D Pos D Pos D 16 Downhearted and blue D D D D 17 Feel pretty worthless D D D D-H 18 Worry about the past Wor D Wor 19 Find life very exciting V Pos W-A W-A-V 20 Hard to get started on projects W-A V W-A W-A-V 21 Feel full of energy V V W W-A-V 22 Situation is hopeless D D D D-H 23 Most people are better off than you D D D D 24 Upset over little things Anx Agit D Agit 25 Often feel like crying D D D D 26 Have trouble concentrating C V C C 27 Enjoy getting up in the morning D Pos D Agit 28 Prefer to avoid social contact W-A W W-A W-A-V 29 Easy to make decisions Anx V C 30 Mind as clear as it used to be V V C C Notes: PCA = principal components analysis; GDS = Geriatic Depression Scale. Mitchell s study used the short form of the GDS (15 items only). Abbreviations for factor names are as follows: Agit = agitation, Anx = anxiety, C = cognitive impairment or concentration, D = dysphoria or depression, D-H = dysphoria hopelessness, Pos = positive items or happiness, V = vigor or energy, W = withdrawal, W-A = withdrawal apathy, Wor = worry. A dash indicates not assigned to a factor. the Geriatric Review Syllabus (Beck, 1991), and by the British Geriatrics Society and the Royal College of General Practitioners (Anderson, 2001). One of the major strengths of the GDS is its simplicity of administration and scoring. It uses a simple yes no response format; therefore, each question counts as 1 point when scored in the depressed direction, for a possible total score of 0 to 30 points. The GDS has well-established internal consistency, with high Cronbach s alpha reliabilities reported, such as.94 (Yesavage et al., 1983),.91 (Parmelee, Lawton, & Katz, 1989), and.87 (Adams, 2001). The scale was designed to yield a single score without subscales. Scoring cutoff points have been suggested in the literature, beginning with the scale s authors, who determined that a score of 11 or above for designating possible depression obtained reasonable specificity and sensitivity with a relatively small sample of older adults (Brink et al., 1982; Yesavage et al., 1983). Subsequent studies have suggested other cutoff points; one study found that 14 points was the optimal cutoff when results on the GDS are compared with those of a clinical psychiatric evaluation (Burke, Nitchter, Roccaforte, & Wengel, 1992). A shorter form of the GDS, the 15-item GDS-S, (Sheikh & Yesavage, 1986) is also widely used by clinicians and researchers and has been found to offer an acceptable substitute for the long form (Lesher & Berryhill, 1994). Despite its prominence and widespread use, few principal components analyses (PCAs) and, to our knowledge, no confirmatory factor analysis (CFA) of the GDS are published in the literature. Four PCAs of the English-language GDS and one of the GDS-S are found in research journals. A summary of the assignment of the scale s items to factors in these studies is shown in Table 1. In the earliest of these published studies, Parmalee and colleagues (1989), using data from a group of 417 institutionalized elders, proposed a factor structure including six factors. They identified the first 14-item factor as Dysphoria, and the subsequent factors as Worry (4 items), Withdrawal Apathy (4 items), Vigor (3 items), Decreased Concentration (2 items), and Anxiety (3 items). Sheikh, Yesavage, Brooks, Friedman, Gratzinger, Hill, Sadeik and Crook (1991) Vol. 44, No. 6,

3 subsequently published a proposed factor structure based on a sample of 326 community-dwelling adults over the age of 65. These authors obtained five reliable factors, from which four of the scale s items were omitted. Although they did not label their factors, their discussion describes the first 9-item factor as sad mood and pessimistic outlook, comparable with the Dysphoria dimension of Parmalee and colleagues (1989); the second as characterized by a lack of mental and physical energy, comparable with the Vigor factor, with some overlap with a cognitive impairment reduced concentration concept (6 items); the third as relating to positive mood and optimism (6 items); the fourth as agitation or restlessness (3 items); and finally, a social withdrawal factor of 2 items (Sheikh et al., 1991, p. 27). Salamero and Marcos (1992), working with data from 234 individuals aged 60 or older in a variety of living situations, obtained a nine-factor solution for the GDS, of which only the first three factors were judged by the researchers to be clinically or theoretically relevant. These three factors were identified (pp ) as depressed mood, again comparable with Dysphoria (13 items); cognitive impairment (3 items); and social withdrawal (4 items). From Table 1, we can see that many of the items for the GDS did not fall into named factors in this analysis, and the authors concluded that the GDS should be considered unidimensional. However, with the smallest most heterogeneous sample size of the five examined here, one may speculate that this study did not adequately capture the relevant dimensions of the GDS. A factor analysis of the 15-item GDS-S (Mitchell, Mathews, & Yesavage, 1993) obtained three dimensions: General Depressive Affect, again resembling Dysphoria (7 items); Life Satisfaction, consisting of the positively worded questions (4 items); and Withdrawal (3 items). Subjects were 868 noninstitutionalized older persons in North Carolina. That study s authors noted that the three factors had lowmoderate to moderate intercorrelations with one another, and that the effects of other demographic and social variables on the three were quite different, leading them to conclude that depression in older adults is multidimensional. Most recently, Adams (2001), working with data from a sample of 327 community-dwelling adults over the age of 65, obtained a six-factor solution of the GDS. This solution most resembled the results of Parmalee and colleagues (1989) already discussed, albeit with a split in the Dysphoria items into two separate factors, one that included those items that involve negative affect and the lack of positive affect (9 items) and the other that included items about hopelessness, worthlessness, and helplessness (4 items). This exploratory factor analysis also obtained a combined Withdrawal Apathy and (Lack of) Vigor factor (6 items), an Anxiety factor (4 items), a Mental Impairment factor (4 items), and an Agitation factor (3 items). In accord with the study by Mitchell and associates (1993), Adams also found differences in endorsement rates and in the zero-order correlations of the factors with demographic and health variables that suggest the GDS could be tapping several distinct clusters of symptoms. As a case in point, Adams has provisionally proposed that the withdrawal apathy and lack of vigor dimension may be indicative of a depletion syndrome related to advanced age and functional impairment (2001). Both commonalities and differences are apparent among the five extant factor analyses of the GDS or the GDS-S. Each of these solutions includes at least one dimension that represents depressive affect or dysphoria, and one that represents social withdrawal. In addition, several of the analyses obtained a dimension involving cognitive impairment or lack of concentration, and an anxiety, worry, or agitation dimension. The analysis by Parmalee and colleagues (1989) grouped positively stated items into a Vigor factor, and two other studies reported that positive items clustered into a Life Satisfaction and a Positive Mood Optimism factor (Mitchell et al., 1993; Sheikh et al., 1991). The two remaining studies obtained results with mixed positive and negative items within factors. Regardless of the obvious similarities in the results from these studies, however, without the next step of a CFA on the GDS to provide evidence that the factor structure remains tenable in a new independent sample, investigators are left without a way of identifying reliable subscales that may represent distinct dimensions or subtypes of depression in older adults. The current study describes a CFA of the GDS. The authors compared the PCA structure of the GDS obtained from a community-dwelling sample in an earlier study (Adams, 2001) with GDS data from a second sample of older adults in independent-living communities (Adams, Sanders, & Auth, in press) to determine how well the original factor structure fits the new data. We chose to use the first set of data as the criterion data set for several reasons. First, we have complete access to the data and the earlier analyses that were done; second, a sample of essentially well noninstitutionalized elders was appropriate for examining the measurement properties of the scale with a minimum of confounding variables; and lastly, as noted herein, the first sample s PCA obtained was quite similar to that published earlier by Parmalee and associates (1989), thus lending credence to our results. We discuss potential implications of the resulting CFA for use and interpretation of the GDS. Methods Participants We obtained the sample for the first set of data from a one-time anonymous mailed survey of older 820 The Gerontologist

4 members of a regional health maintenance organization (HMO) in Maryland. A total of 327 completed surveys were received with a 38% response rate. One of our goals in this study was to determine the prevalence of depressive symptoms among older members of the HMO; another was to examine the factor structure of the GDS and the correlates of the factors with health and demographic characteristics (Adams, 2001); and another was to test a new measure of the change in interests and activities in older adults and compare results of that measure with those of the GDS (Adams, 2004). All respondents were aged 65 years or older, with a mean age of 73.2 (66.2), and all were living in the community. This sample was almost equally distributed between men and women; about 88% of the participants were Caucasian, and the participants were of mixed religious backgrounds. The mean score on the GDS for this original sample was 4.92, with 12.9% of respondents scoring above the cutoff suggestive of depression (11 points or higher). The comparison sample consisted of residents of two Methodist-affiliated retirement facilities in Pennsylvania. The facilities were age-segregated apartment communities with optional activities, access to health care, and an emergency response system provided for residents. We gathered these data by use of a one-time questionnaire placed into the mailboxes of residents. Our goals in this second study were to examine the prevalence of loneliness and depressive symptoms and relationships among these two constructs, social network, and participation in social and leisure activities for residents in independent living (Adams et al., in press). For the current study, 60 additional cases from assisted living were also used. The combined N = 294. All of these respondents were over the age of 60, about two thirds were female, and nearly all were Caucasian and Protestant. Mean GDS score for this comparison sample was 7.47, with 26.2% of the sample scoring at or above the depression cutoff. Data Analysis The PCA for the original sample s data explained 50.4% of the variance in the GDS items. Although nine eigenvalues over 1 were initially obtained, Cattell s scree plot suggested a final solution of six components. Varimax rotation converged in nine iterations and the final eigenvalues were as follows: 3.524, 2.818, 2.387, 2.344, 2.312, and (Adams, 2001). We estimated the proposed six-factor measurement model with data from the second sample by using a CFA method with the LISREL 8 statistical program. Following the suggestion of Kline (1998), we performed a tetrachoric transformation of the covariance matrix prior to estimation of the measurement model to provide an asymptotic covariance matrix to account for the nonnormal data distribution that was due to the dichotomous nature of the item response set. It is customary practice to present the chi-square significance test along with other measures of overall model fit that represent total variance accounted for in the sample matrix by the estimated model, the proportion of variance accounted for after adjusting for degrees of freedom, and the extent of error represented between the sample and estimated matrices (Bollen, 1989; Kline, 1998). Therefore, we selected the chi-square test, goodness-of-fit index (GFI), adjusted GFI (AGFI), and standardized root mean square residual as fit indices. Our process of analysis started with the full six factors and all of the items, and then we used a nested models approach to test alternative nested structures with reduced parameters to test fit improvement. We used the chi-square difference statistic to test the significance of the change in the chi-square test for each alternative model over the full model. Results Full Model We analyzed the full six-factor measurement model for the 30-item GDS by using the six item clusters derived from the exploratory PCA. Table 2 shows these six factors and their respective items, along with the standardized lambda coefficients for the items using data from Sample 2. For Dysphoric Mood, labeled DYS 1 (nine items), the lambdas ranged from.40 to.64; Item 16, downhearted and blue (k =.64), Item 3, feeling life is empty (k =.61), and Item 9, happy most of the time (k =.54), showed the highest validity coefficients for this factor. The standardized lambda coefficients for the Withdrawal Apathy Lack of Vigor factor (six items), labeled WAV, ranged from.45 to.55; Item 21, full of energy (k =.55), Item 28, avoid social gatherings (k=.51), and Item 20, hard to start new projects (k =.51) showed the highest validity coefficients for this factor. The ANX or Worry factor, composed of four items, showed lambda estimates that ranged from.48 to.54; Item 13, worry about the future (k =.54), and Item 6, bothered by thoughts (k =.52), were the best-fitting items on this construct. The MENT or Cognitive Impairment factor (four items) showed lambda estimates that ranged from.30 to.55. Item 26, trouble concentrating (k =.55), and Item 30, mind as clear (k =.48), were the strongest items, and Item 14, problems with memory (k =.30), showed poor construct fit and was the lowest validity coefficient for all GDS items. DYS 2 or Hopelessness (four items) showed lambda estimates that ranged from.46 to.60; Item 22, feel situation is hopeless (k =.60), and Item 10, often feel helpless (k =.57), showed the best construct fit. The sixth factor that we identified in the PCA, AGIT (Agitation; three items) Vol. 44, No. 6,

5 Table 2. Confirmatory Factor Analysis Full and Alternative Models for the Geriatric Depression Scale Factor (Subscale Name) showed consistently poor-fitting items when we analyzed it with confirmatory methods. The lambda coefficients for all three items were below.40. These items, restless and fidgety, frequently get upset, and enjoy getting up in the morning do not appear to be empirically related to this Agitation construct. Alternative Model Full Model Alternate Model GDS Item No. and Wording k SMC k SMC DYS 1 (Dysphoric Mood) 16 Downhearted and blue Happy most of the time Feel life is empty Basically satisfied with life Most people are better off In good spirits Often get bored Often feel like crying Wonderful to be alive WAV (Withdrawal Apathy Vigor) 12 Prefer to stay home Avoid social gatherings Dropped activities and interests Find life very exciting Hard to start new projects Full of energy ANX (Worry) 8 Afraid something bad will happen Worry about the future Bothered by thoughts Worry a lot about the past MENT (Cognitive Impairment) 14 More problems with memory than most N/A N/A 26 Trouble concentrating Mind as clear as it used to be Easy to make decisions DYS 2 (Hopelessness) 22 Feel situation is hopeless Often feel helpless Feel pretty worthless Hopeful about the future AGIT (Agitation) 11 Restless and fidgety N/A N/A 24 Frequently get upset N/A N/A 27 Enjoy getting up in the morning N/A N/A Note: k = standardized validity coefficient; SMC = squared multiple correlation; N/A = not assigned. We used a nested model approach to test alternatives to the full six-factor model. From the Table 3. Goodness-of-Fit Statistics for Confirmatory Factor Analysis Models of the Geriatric Depression Scale Model v 2 df Significance GFI AGFI St. RMR Full Alternative Note: GFI = goodness-of-fit index; AGFI = adjusted GFI; St. RMR = standardized root mean square residual. results of this first full model that replicated the measurement structure derived from the original PCA, we proposed an alternative model that eliminated the poor-fitting Agitation construct and eliminated the one Cognitive Impairment item (Item 14, problems with memory ) that showed the lowest validity estimate of all GDS items. Hence, the first alternative model retained five original factors (DYS 1, WAV, ANX, MENT, and DYS 2) and eliminated the poorest fitting item, Item 14, resulting in 26 items. As shown in Table 2, the standardized validity coefficients of the alternative model remained similar to the full model estimates. The alternative model showed overall improvement over the full six-factor model (see Table 3), with a likelihood ratio (chisquare difference of , degrees of freedom difference of 101) that is significant at the.10 level (p =.073). The alternative model s GFI =.90, the recommended criterion, and the standardized root mean square residual, an estimate of error between the observed and estimated models, hovered around the recommended criterion of.05. We tested second and third alternative models that further reduced the number of factors. The second alternative combined DYS 1, DYS 2, and ANX into one collapsed mood factor because of their high intercorrelations, and then used MENT, AGIT, and WAV. The resulting values were v 2 = , df = 399 (p =.015), standardized root mean square residual =.056, GFI =.99, and AGFI =.86. This did not appear to be too different from the first alternative. We tested a third alternative that was identical to this but with AGIT removed. This resulted in values of v 2 = , df = 321 (p =.031), standardized root mean square =.055, GFI =.89, and AGFI =.87. Neither of the chi-square differences for these two additional alternatives showed a statistically significant improvement over the first alternative, and, conceptually, some meaning was lost by combining the mood items; thus we selected the first alternative model for use. Interitem Reliabilities and Zero-Order Correlations of the Five Factors Cronbach s alpha reliability coefficients for the five remaining factors in the alternate model are shown in Table 4. The Dysphoric Mood, Withdrawal Apathy Vigor, and Hopelessness factors each 822 The Gerontologist

6 Table 4. Cronbach s Alpha Reliability Coefficients of the GDS and its Proposed Subscales Score No. of Items Cronbach s a Sample n Dysphoric Mood Withdrawal Apathy Vigor Hopelessness Worry Cognitive Impairment GDS total Note: The Geriatric Depression Scale (GDS) total excludes the four items omitted from the Alternative Measurement Model. have alpha reliabilities that suggest they could be considered as standalone variables. Worry and Cognitive factors have lower alpha coefficients, in part due to lower item counts. The zero-order correlation matrix for the five factors is shown in Table 5. Each of the correlations is significant at the.01 level. As may be expected, the factors labeled Dysphoric Mood and Hopelessness have the highest correlation at r =.722. The Cognitive factor has the lowest absolute correlations except to Withdrawal Apathy Vigor, with which it is moderately correlated. Worry is quite highly correlated with both of the Dysphoric Mood factors, but less with Cognitive or Withdrawal Apathy Vigor. Finally, for the second, independent living facilities sample, mean subscale scores, standard deviations, and the number and percentage of respondents endorsing at least one item on the subscale are displayed in Table 6. Withdrawal Apathy Vigor has the highest mean score for the sample, and the highest proportion of respondents who endorsed one or more items (84.5%). Dysphoric Mood has the next highest mean score. Cognitive Impairment has the next highest proportion of respondents who endorsed any of its items (66.8%). At the other end of the spectrum, Hopelessness has the lowest proportion of respondents to endorse any of its items (40.6%) and the lowest mean score. Discussion This study has presented a five-factor measurement model estimated with CFA methods that shows Table 5. Zero-Order Correlations Among Subscale Scores of the Geriatric Depression Scale Subscale Dysphoric Mood.409**.722**.617**.234** 2. Withdrawal Apathy Vigor.409**.427**.332**.442** 3. Hopelessness.722**.427**.596**.266** 4. Worry.617**.332**.596**.247** 5. Cognitive Impairment.234**.442**.266**.247** ** p,.001. Table 6. Means, Standard Deviations, and Proportion of Endorsement for Proposed Subscale Scores of the GDS in a Retirement Community Sample Subscale Sample n M SD % Endorsing at Least One Item Dysphoric Mood Hopelessness Withdrawal Apathy Vigor Worry Cognitive Note: GDS = Geriatric Depression Scale. good overall fit using 26 items of the GDS. These five factors were originally derived from an exploratory PCA obtained from a community-dwelling sample of older adults (Adams, 2001), and we retained them in this CFA with an independent sample of older adults residing in independent-living facilities. The five factors appear to represent several distinct symptom clusters. As Mitchell and colleagues (1993) suggested in their study of the multidimensionality of the GDS- S, the separate subdimensions of depression should be interpreted individually, because grouping the individual dimensions of depression into a single score may suppress potential differences by subdimension, (p. 214). In the current study using the full GDS, we have specified five subdimensions of geriatric depression that present possibilities for use as subscales in the administration and interpretation of the scale. The DYS 1 or Dysphoric Mood factor consists of 9 items that describe depressed mood, sadness, or emptiness as well as a lack of satisfaction with life and a lack of happiness. There is a mix of positively and negatively stated items. Each of the other proposed factor structures of the GDS in the literature have an initial factor that contains many of these same items and appears to represent the core of depressed mood within the scale. Comparing these results with the 15 items that comprise the GDS Short Form (Sheikh & Yesavage, 1986), we note that 7 of the items that were selected for the GDS-S fall into this Dysphoric Mood factor. The DYS 2 factor consists of four items that deal with hopelessness, helplessness, and worthlessness, and we have labeled it Hopelessness. There is a desperate quality to each of these items that sets them apart. It is noteworthy that the mean endorsement or score for this DYS 2 factor is far lower than that for DYS 1. Studies of suicidal persons have found that hopelessness is predictive of suicidal ideation (Brown, Beck, Steer, & Grisham, 2000; Szanto et al., 2002). Certainly, feelings of worthlessness and helplessness also may be associated with wishes to die, or at least low motivation to continue living. Thus, this Hopelessness factor may be of particular importance in screening older adults for suicidal Vol. 44, No. 6,

7 ideation or intent. Three of the four items related to hopelessness also appear in the GDS-S. The six items in the WAV factor were originally found, along with one additional item, in two separate factors identified in the PCA by Parmalee and colleagues (1989). Four of the Withdrawal Apathy Vigor items also loaded on a withdrawal factor in the PCA by Salamero and Marcos (1992), and three of them are in the withdrawal factor found in the PCA of the GDS-S cited earlier (Mitchell et al., 1996). This WAV factor has the highest mean score for the respondents and the lowest proportion of nonendorsement of any of the factors. Higher endorsement simply means these items are more common among the sample, both those respondents with and without scores in the depressed range for the total scale. A similar result was obtained in the study with the original sample (Adams, 2001), where WAV was also found to have a stronger association than the other GDS factors with age and health problems. Thus, Adams (2001) has suggested that WAV represents behaviors and experiences that are influenced by age and physical frailties and may be akin to a depletion syndrome. The ANX factor, like the Hopelessness (DYS 2) factor, is not highly endorsed within this sample. Its mean score of.7169 is the second lowest of the five factors. The four items each describe some kind of obsessive ruminating or worry, whether about the future or the past, so that Worry appears to be an apt name for the factor. These items concerning worry capture symptoms related to thinking and emotion that are commonly found in depressed persons of all ages. In contrast, the three agitation items, which have not been retained in the alternative model, appear to capture symptoms that are more clearly physical or behavioral. The agitation items may have a number of underlying causes and did not hold together well as a dimension in this sample of older adults. The Cognitive Impairment factor performed better after we removed one item from it in the alternative model. This item Do you feel you have more problems with memory than most? did not load highly on the mental impairment construct. Interestingly, the same item did not load on any factor in the PCA proposed by Mitchell and associates (1993) for the GDS-S or the PCA by Sheikh and associates (1991) for the GDS long form. There may be two problems with that item. First, older adults may perceive that they have memory problems for a number of reasons, and thus the item may not be predictive of depression, although this could be said for many of the items on the GDS. The bigger problem may be the ambiguity inherent in deciding whether or not one has more memory problems than most. Does this mean most others of similar age, most others who live in the same facility, or most other persons of any age? It is likely that interpretation of this item will differ according to the residential setting and the available reference group of the respondent, which would suggest that older persons in an institutional setting who see a number of people suffering with dementia may tend to answer in the negative more often than older persons residing in the community. After removal of that problematic item, the remaining cognitive items address confusion, difficulties with decision making, and reduced concentration. That this Cognitive subscale represents a distinct set of symptoms is illustrated by its stronger association with the Withdrawal Apathy Vigor factor than with the Dysphoric Mood, Hopelessness, or Worry factors, all of which represent the core of depressive symptoms. Although these cognitive symptoms may be hallmarks of depression, they may also be caused by other conditions, such as early dementia, strokes, certain medications, or normal changes of later old age. A higher score on the Cognitive subscale could be an indication to pursue more extensive mental status testing. There are certain limitations inherent in this study. First and foremost is that the CFA presented here was based on two data sets obtained from convenience samples of older adults rather than randomly selected samples of a targeted underlying population. The samples also were not representative of diverse racial or cultural groups. Because these analyses were conducted with homogeneous, nonprobability samples of relatively modest size, and because this is the first CFA of the scale in the literature, we would recommend interpreting these findings with some caution and consider the subscales of the GDS to be preliminary in nature, pending further validation by investigators in other settings. It is possible that these results will not crossvalidate in future studies, so we do not recommend their use for clinical decision making as yet. However, the model presented here has obtained adequate GFI indices, appears to have good face validity, lends itself to easy interpretation, and does not stray too far from the previously published exploratory factor structures, as was shown in Table 1. In light of these promising aspects of our results, we see potential utility in beginning to use the three subscale scores that performed best here, that is, Dysphoric Mood, Withdrawal Apathy Vigor, and Hopelessness, in research. These may serve as an adjunct to the familiar well-normed total scale score, to provide more detail about symptoms experienced. A second-order CFA, based on representative samples of older adults, will be necessary to establish the appropriateness of subscale scores over the single scale score. Clinical and Research Implications This article has described what is, to our knowledge, the first CFA following an exploratory PCA of the Geriatric Depression Scale. The resulting 824 The Gerontologist

8 five subscales of the GDS each represents a distinct subdimension of the syndrome we call depression in older adults. As Blazer (2003) has noted in a recent review, there are a number of subtypes of geriatric depression, such as major depressive disorder, minor but clinically significant depression, dysthymia, vascular depression, depression associated with dementia, and melancholia. Each of these presents a different symptom configuration, and each may have a different scoring pattern on depression screening scales. The GDS is already a very popular and well-established screening tool for depression in older adults, but there may be benefits to adopt subscale scoring. This study represents a first step in bringing added precision of measurement to the scale. More research will be needed to see whether these subscales appear to fit the response patterns of a broad range of clinical and community samples. Investigators using the GDS with groups of respondents may wish to take a stepwise approach to scoring it. As noted earlier, we suggest first obtaining the total score as usual, and then conducting an exploratory factor analysis with the group s GDS data in order to identify areas of similarity and difference from the subscales presented in the measurement model here. If there are few serious differences, then the subscale scores suggested here may be used with greater confidence. It would also be appropriate, as with any measure, to obtain Cronbach s alpha reliability coefficients for the subscale scores. Those scores with alphas that meet the investigator s criteria for reliability may be used as additional variables or assessment tools for the respondents in question. Although we remain mindful of the preliminary nature of the data, there are some additional clinical or research implications presented by the specific subscales identified here. The Dysphoric Mood and Hopelessness subscales appear to include the most serious and worrisome depressive symptoms in the scale. Clinicians wishing to evaluate the severity of depression in a given individual or among a group of individuals could use the scores of those two subscales as a type of affective severity index. The Withdrawal Apathy Vigor subscale has received high endorsement from respondents regardless of their depression level, as indicated by the total GDS score, and thus appears to have less discriminant validity for depression, but this may be an indicator of health- or age-related frailty, depletion, or malaise. All three of these subscales produced Cronbach s alphas in the range of in the study sample, which suggests they may hold up as consistent, reliable variables with future samples. In contrast, the Worry and Cognitive Impairment subscales, each with a small number of items, have obtained lower reliability coefficients here. We have also noted that these two subscales may be tapping symptoms that frequently accompany depression but may also be indicative of a number of other conditions. Depending on their study aims, investigators will now have the opportunity to use only the most reliable subscales or the most clearly depression-related subscales from the total GDS. The findings of this study also may have implications for use of the GDS Short Form. The 15 items of that version of the scale include 7 from this study s Dysphoric Mood subscale, 3 from the Hopelessness subscale, 3 from Withdrawal Apathy Vigor, 1 from Worry, and 1 from Cognitive Impairment. The distribution of the GDS Short Form items across these new subscales is quite congruent with the structure we have obtained for the full scale, and the importance we would tend to assign to individual items. One exception is the cognitive item assigned to the GDS Short Form (Do you have more problems with memory than most?), which unfortunately is one that was omitted from our final model because of very low factor loading. The diagnostic or research utility of the existing GDS Short Form versus use of two or three of these suggested subscales from the full GDS is a question that future research may examine empirically. This study used data from two convenience samples of mostly Caucasian older adults to obtain a CFA of the widely used Geriatric Depression Scale. Using data from older adults who live in the community or in independent-living facilities, we have found that three subscales of the GDS representing distinct symptom clusters have performed adequately and have proved consistent with previous factor analytic studies. The two remaining subscales evidenced poor internal consistency for this sample. 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