Arthritis self-efficacy is important for successful disease management. This study examined psychometric properties of the 8-item English version of the Arthritis Self-Efficacy Scale (ASES-8) and differences in ASES-8 scores across sample subgroups. In 401 participants with self-reported doctor-diagnosed arthritis, exploratory factor analysis and tests of internal consistency were conducted. Concurrent validity was examined by associating ASES-8 scores with disease-specific, psychosocial, functional, and behavioral measures expected to be related to arthritis self-efficacy. All analyses were conducted for the full sample and within subgroups (gender, race, age, education, and weight status). Exploratory factor analysis for the entire sample and in all 12 subgroups demonstrated a one factor solution (factor loadings: 0.61 to 0.89). Internal consistency was high for measures of Cronbach’s alpha (0.87 to 0.94), omega (0.87 to 0.93), and greatest lower bound (0.90 to 0.95). ASES-8 scores were significantly correlated with all measures assessed
Successful chronic disease management is contingent upon positive health behaviors, such as performing physical activity, adhering to appropriate medications, and eating a healthy diet. To help explain why certain people engage in healthier behavior than others, behavioral theories commonly incorporate self-efficacy or closely related constructs [
Several scales are available to measure arthritis management self-efficacy. As part of the Stanford Arthritis Self-Management Study, the Arthritis Self-Efficacy Scale (ASES) was developed to be inclusive of all types of arthritis [
The purpose of this paper was to report the psychometric properties of the ASES-8 using a large and diverse sample of persons with arthritis. Specific goals were to (a) report the factor structure of the ASES-8, (b) assess the reliability (internal consistency) of the ASES-8, and (c) assess the concurrent validity of the ASES-8 by correlating it with measures for which the literature supports a relationship. These goals were applied to the sample as a whole as well as to subgroups according to gender, race, age, education, and weight status. This paper also examined whether ASES-8 scores differed according to gender, race, age, education, or weight status.
Participants were recruited to take part in a randomized controlled trial that compared a self-directed exercise program to a self-directed nutrition program. Baseline data were used for this paper. Participants were recruited in a variety of ways with newspaper advertisements and worksite Listservs being the most successful. Potential participants were screened by telephone. Those who were at least 18 years old, had self-reported doctor-diagnosed arthritis, and experienced at least one symptom of arthritis (joint pain, stiffness, tenderness, decreased range of motion, redness and warmth, deformity, crackling/grating, or fatigue) were eligible for this study. Individuals were excluded if they had conditions that would be contraindications to physical activity or if they were already physically active.
Those who remained eligible and interested in the study participated in baseline measurement sessions. Prior to the scheduled measurement session, participants were mailed an informed consent form approved by the Institutional Review Board at the University of South Carolina and a survey. At the baseline measurement session, participants reviewed and signed the informed consent form, the survey was collected, and staff administered physical measurements and functional performance tests. Participants received a small cash incentive for taking part in the baseline measurement session.
The GAITRite (CIR Systems, Havertown, PA), a portable walking mat with software, measured gait speed in meters/second [
The 30-second chair stand measured lower body strength [
Analyses of internal consistency were conducted using R (Free Software Foundation, Inc., Boston, MA). All other analyses were conducted using SAS version 9.3 (SAS Institute, Cary, North Carolina). An exploratory factor analysis was conducted with responses to the ASES-8. The principal factor method was used. Four criteria were used to determine the number of factors: (a) eigenvalues had to be greater than 1.0 and had to explain at least 10% of the common variance, (b) visual examination of the screen plot was conducted to determine number of eigenvalues preceding the “elbow,” (c) item loadings had to exceed 0.40, and (d) the factor had to be interpretable. Consistent with recommendations by Peters [
The study recruited 401 participants. Sample characteristics are shown in Table
Sample characteristics (
Characteristic | % ( |
Mean (SD) | Range |
---|---|---|---|
Gender, % | |||
Men | 14.21 (57) | ||
Women | 85.79 (344) | ||
Race, % | |||
White | 64.00 (256) | ||
African American | 35.25 (141) | ||
Other races or biracial | 0.75 (3) | ||
Age group, % | |||
18–44 years | 12.75 (51) | ||
45–64 years | 65.50 (262) | ||
64+ years | 21.75 (87) | ||
Educational attainment, % | |||
Less than college graduate | 39.25 (157) | ||
College graduate | 60.75 (243) | ||
Weight status, % | |||
Normal weight | 14.50 (58) | ||
Overweight | 28.50 (114) | ||
Obese | 57.00 (228) | ||
Arthritis self-efficacy | 6.32 (2.12) | 0–10 | |
Arthritis symptoms, % | |||
Pain | 4.71 (2.32) | 0–10 | |
Fatigue | 4.99 (2.65) | 0–10 | |
Stiffness | 5.32 (2.55) | 0–10 | |
Depressive symptoms | 6.47 (5.14) | 0–28 | |
HRQOL, days impaired in past month | 10.42 (10.70) | 0–30 | |
Self-rated health (1 = poor; 5 = excellent) | 3.07 (0.83) | 1–5 | |
Self-reported disability (3 = most disabled) | 0.63 (0.52) | 0–2 | |
Functional performance | |||
6-minute walk, meters | 494.05 (91.22) | 151.46–721.57 | |
Gait speed, meters/second | 1.09 (0.22) | 0.39–1.72 | |
Chair stands, number in 30 seconds | 9.99 (3.48) | 0–24 | |
Total PA, hours/week | 9.94 (7.37) | 0–46.75 |
Note: not all numbers sum to 401 due to missing data. HRQOL = health-related quality of life; min = minute; total PA = light-, moderate-, and vigorous-intensity physical activity.
The exploratory factor analysis for the full sample indicated only one eigenvalue above 1.0 (5.09), and this result was visually confirmed on the scree plot. Each item in the ASES-8 loaded onto the single factor for the full sample. Factor loadings for each item were between 0.70 and 0.87 (see Table
Factor loadings for one factor solution and reliability measures (Cronbach’s
Item number | Full sample | Gender | Race | Age group | Educational attainment | Weight status | |||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Women | Men | White* | Af Am | 18–45* | 46–64 | 65+ | Not college grad* | College grad | Normal | Overweight | Obese | ||
1 | 0.72 | 0.74 | 0.61 | 0.69 | 0.79 | 0.61 | 0.75 | 0.71 | 0.74 | 0.70 | 0.56 | 0.76 | 0.75 |
2 | 0.78 | 0.80 | 0.62 | 0.73 | 0.85 | 0.67 | 0.80 | 0.80 | 0.77 | 0.78 | 0.73 | 0.80 | 0.79 |
3 | 0.87 | 0.87 | 0.85 | 0.84 | 0.91 | 0.89 | 0.85 | 0.90 | 0.88 | 0.86 | 0.88 | 0.84 | 0.88 |
4 | 0.86 | 0.86 | 0.83 | 0.83 | 0.89 | 0.89 | 0.83 | 0.91 | 0.87 | 0.84 | 0.85 | 0.88 | 0.84 |
5 | 0.87 | 0.87 | 0.83 | 0.84 | 0.89 | 0.87 | 0.86 | 0.88 | 0.89 | 0.84 | 0.85 | 0.89 | 0.85 |
6 | 0.70 | 0.69 | 0.75 | 0.65 | 0.74 | 0.69 | 0.69 | 0.71 | 0.72 | 0.65 | 0.73 | 0.74 | 0.67 |
7 | 0.84 | 0.85 | 0.73 | 0.80 | 0.88 | 0.84 | 0.84 | 0.82 | 0.84 | 0.83 | 0.87 | 0.85 | 0.82 |
8 | 0.74 | 0.73 | 0.79 | 0.70 | 0.77 | 0.75 | 0.74 | 0.71 | 0.71 | 0.74 | 0.71 | 0.72 | 0.75 |
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0.89 | 0.90 | 0.89 | 0.87 | 0.94 | 0.91 | 0.92 | 0.89 | 0.91 | 0.91 | 0.88 | 0.93 | 0.92 |
Omega | 0.90 | 0.90 | 0.89 | 0.87 | 0.94 | 0.91 | 0.92 | 0.90 | 0.91 | 0.91 | 0.88 | 0.93 | 0.92 |
GLB | 0.92 | 0.93 | 0.93 | 0.90 | 0.96 | 0.95 | 0.95 | 0.92 | 0.94 | 0.94 | 0.94 | 0.95 | 0.94 |
Note: Af Am = African American. GLB = greatest lower bound. *A two-factor solution was obtained, but the second factor had a small eigenvalue (1.1 for whites, 1.0 for those of 18–45 years, and 1.1 for not college grad). Sample sizes were <100 for men, those of 18–44 years, those of 65+ years, and those who had a normal body weight. All items except item 7 started with the phrase “How certain are you that you can…” and ended with “decrease your pain quite a bit?” (1), “keep your arthritis or fibromyalgia pain from interfering with your sleep?” (2), “keep your arthritis or fibromyalgia pain from interfering with the things you want to do?” (3), “regulate your activity so as to be active without aggravating your arthritis or fibromyalgia?” (4), “keep the fatigue caused by your arthritis or fibromyalgia from interfering with the things you want to do?” (5), “do something to help yourself feel better if you are feeling blue?” (6), and “deal with the frustration of arthritis or fibromyalgia?” (8). Question 7 was worded as follows: “As compared with other people with arthritis or fibromyalgia like yours, how certain are you that you can manage pain during your daily activities?”
Subgroup analyses (see Table
Measures of internal consistency (see Table
As shown in Table
Correlations between arthritis self-efficacy and health-related variables, overall and by sample subgroups.
Variable | Full sample | Gender | Race | Age group | Educational attainment | Weight status | |||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Women | Men | White | Af Am | 18–45 | 46–64 | 65+ | Not college grad | College grad | Normal | Overweight | Obese | ||
Pain | −0.39* | −0.39* | −0.43* | −0.35* | −0.44* | −0.48* | −0.42* | −0.26* | −0.32* | −0.41* | −0.39* | −0.38* | −0.40* |
Fatigue | −0.41* | −0.42* | −0.32* | −0.41* | −0.39* | −0.35* | −0.49* | −0.23* | −0.34* | −0.44* | −0.41* | −0.38* | −0.43* |
Stiffness | −0.39* | −0.37* | −0.53* | −0.39* | −0.38* | −0.57* | −0.41* | −0.24* | −0.32* | −0.41* | −0.47* | −0.33* | −0.41* |
Depressive |
−0.43* | −0.43* | −0.47* | −0.45* | −0.42* | −0.60* | −0.45* | −0.28* | −0.40* | −0.43* | −0.52* | −0.46* | −0.38* |
HRQOL | −0.41* | −0.38* | −0.54* | −0.43* | −0.38* | −0.35* | −0.42* | −0.40* | −0.41* | −0.38* | −0.46* | −0.47* | −0.36* |
Self-rated health | 0.32* | 0.36* | 0.07 | 0.31* | 0.33* | 0.46* | 0.30* | 0.29* | 0.33* | 0.29* | 0.50* | 0.32* | 0.27* |
Disability | −0.43* | −0.41* | −0.52* | −0.38* | −0.47* | −0.66* | −0.42* | −0.33* | −0.44* | −0.37* | −0.57* | −0.22 | −0.51* |
6-min walk | 0.24* | 0.23* | 0.26 | 0.21* | 0.27* | 0.15 | 0.27* | 0.24* | 0.14 | 0.28* | 0.42* | 0.13 | 0.26* |
Gait speed | 0.18* | 0.20* | 0.04 | 0.14* | 0.23* | 0.09 | 0.17* | 0.30* | 0.12 | 0.19* | 0.42* | 0.06 | 0.19* |
Chair stands | 0.25* | 0.26* | 0.13 | 0.28* | 0.22* | 0.34* | 0.22* | 0.33* | 0.15 | 0.29* | 0.42* | 0.13 | 0.28* |
Total PA | 0.15* | 0.16* | 0.12 | 0.14* | 0.13 | 0.25 | 0.10 | 0.23* | 0.14 | 0.13* | 0.36* | 0.11 | 0.13* |
Note: Af Am = African American; HRQOL = health-related quality of life (higher indicates more impairment); min = minute; total PA = light-, moderate-, and vigorous-intensity physical activity. Due to skewed distribution, a square root transformation was used for depressive symptoms, HRQOL, and total PA. *indicates
Arthritis symptoms (pain, fatigue, and stiffness), depressive symptoms, more impaired health-related quality of life, and self-reported disability were negatively and significantly related to ASES-8 scores in all 12 subgroups. The magnitude of correlations ranged from
Scores on the ASES-8 were similar for men and women,
Arthritis management self-efficacy, the belief in one’s ability to manage the symptoms of arthritis, is a central component of chronic disease management. The purpose of this paper was to examine the factor structure, reliability, and validity of the ASES-8, a tool that can lessen respondent burden when compared to the original 20-item version. Our results support the use of the ASES-8 as a reliable and valid scale to measure arthritis self-efficacy.
For the sample as a whole, a one factor solution was found, with all items loading heavily on this factor. This same factor structure was seen for all subgroups. Although there was a second eigenvalue above 1.0 for 3 of the 12 subgroups (those who are whites, those of 18–45 years, and those without a college degree), the other criteria were not met for the second factor. Cronbach’s alpha was also very high in the full sample and in all subgroups, consistent with reports of the German [
There were several limitations to this study. Because the primary focus of the larger study was not to evaluate the psychometric properties of the scale, some subgroups had small sample sizes and may have been underpowered to detect associations. Samples sizes for men, those of 18–44 years, those of 65+ years, and those who were of normal weight were less than 100 individuals per subgroup. Women, whites, and those with a college degree were the most highly represented in the sample. Due to the use of secondary data, we were also unable to examine the test-retest reliability or divergent validity of the scale. We also recognize that an inherent limitation of survey measures of self-efficacy is that they may not be applicable to a given individual and may lack specificity when applied to an individual in treatment settings.
Furthermore, the cross-sectional study design does not allow us to make causal inferences. Those who report lower symptoms of arthritis, for example, may inherently feel more confident in their ability to manage arthritis than those with higher symptomatology. However, Arnstein and colleagues showed that self-efficacy mediated the relationship between pain intensity and disability among those with chronic pain and was a stronger mediator than was depression [
The primary strengths of the study include the large sample (
Despite the importance of arthritis management self-efficacy and the appeal of using an abbreviated measure, studies have not examined the psychometric properties of the ASES-8. This study demonstrated the factor structure, reliability, and concurrent validity of the scale for a diverse sample of adults with arthritis and in sociodemographic subgroups.
The authors declare that there is no conflict of interests regarding the publication of this paper.
This research was supported by the Centers for Disease Control and Prevention’s National Center for Chronic Disease Prevention and Health Promotion by Cooperative Agreement no. U48-DP-001936, Special Interest Project (SIP) 09-028. The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention or the Department of Health and Human Services. The authors thank the study participants and research investigators, staff, and students for their important contributions.