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RESEARCH ARTICLE |
1 Oregon Research Institute, Eugene.
2 Department of Exercise Science, Willamette University, Salem, Oregon.
3 Department of Kinesiology, University of Illinois at Urbana-Champaign.
Address correspondence to Fuzhong Li, PhD, Oregon Research Institute, 1715 Franklin Boulevard, Eugene, OR 97403. E-mail: fuzhongl{at}ori.org
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Abstract |
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FEAR of falling has been viewed as a significant health problem for older adults (Howland, Peterson, & Lachman, 2001
; Kristine, 2002). A key public health concern is that increases in the level of fear of falling can result in self-induced restrictions in daily activity that could lead to muscle and lower-extremity strength depletion, thus restricting mobility and consequently reducing physical functioning (Arfken, Lach, Birge, & Miller, 1994; Chandler, Duncan, Sanders, & Studenski, 1996; Lachman et al., 1998; Li, Fisher, Harmer, McAuley, & Wilson, 2003; Maki, Holliday, & Topper, 1991; Tinetti, 1995; Vellas, Wayne, Romero, Baumgartner, & Garry, 1997). Because of its negative health and social consequences, fear of falling has been treated as either a direct or indirect target for intervention (Li et al., in press; Tennstedt et al., 1998; Walker & Howland, 1991).
In the gerontology literature, fear of falling has often been studied within a self-efficacy framework. Self-efficacy, defined as "beliefs in one's capabilities to organize and execute the courses of action required to produce a given attainment" (Bandura, 1997, p. 3), plays a central role in explaining human motivation and behavior (Bandura, 1986, 1997, 2004). Beliefs of personal efficacy have been found to mediate emotional, cognitive, and behavioral patterns in a wide range of domains of psychosocial and physical functioning (Bandura, 1986, 1997). In the area of fear of falling, self-efficacy has been studied with respect to falls self-efficacy, which refers to personal beliefs in one's ability to engage in certain activities of daily living without falling or losing balance (Powell & Myers, 1995; Tinetti, Richman, & Powell, 1990). Accordingly, fall-related efficacy measures have been developed that are based on this conceptual premise (e.g., Lawrence et al., 1998; McAuley, Mihalko, & Rosengren, 1997; Powell & Myers, 1995; Tinetti et al., 1990). Depending on the research design, falls self-efficacy has been studied as either a process variable or an outcome variable. For example, a cross-sectional analysis has found that falls self-efficacy mediates the relationship between fear of falling and functional ability in older adults (Li, Fisher, Harmer, & McAuley, 2002). As an outcome variable, falls self-efficacy has been used as a targeted intervention outcome. For example, Tennstedt and colleagues (1998) showed that a short-term cognitive–behavioral intervention was able to increase falls efficacy among older adults who were compliant in a 6-week intervention protocol.
Exercise intervention has been advocated as a means to improve muscle strength and balance and to reduce falls and fear of falling in older adults (American Geriatrics Society, British Geriatrics Society, and American Academy of Orthopaedic Surgeons Panel on Falls Prevention, 2001; Howland et al., 2001). Among many types of exercise modalities, Tai Chi has received considerable research attention in recent years as a therapeutic exercise for improving physical performance and functional balance and for reducing fall-related risks (Li et al., 2004, in press; Wolf et al., 1996, 2003), including fear of falling (Li et al., in press). The study by Li and colleagues (in press) showed that, among other health outcomes, a 6-month Tai Chi intervention significantly reduced fear of falling in adults aged 70 and older. Tai Chi participants had a 55% reduction in fear of falling (operationalized by the Survey of Activities and Fear of Falling in the Elderly, or SAFFE; see Lachman et al., 1998), compared with a 13% reduction for those assigned to a stretching control condition. Although such findings from a Tai Chi intervention are important from a fall-prevention perspective, they provide little information relative to the underlying mechanisms that may produce such effects. Further efforts are therefore needed to consider intervention or treatment mediators that help identify causal pathways between treatment and outcome, and possible mechanisms through which a treatment might achieve its effects (Kraemer, Wilson, Fairburn, & Agras, 2002).
In the present study, we addressed this issue of intervention mechanisms by examining exercise intervention response patterns (i.e., fear of falling) in subgroups defined by levels of falls self-efficacy. Social cognitive theory (Bandura, 1986, 1997) would propose that skill acquisition and guided mastery practices through participation in a Tai Chi program are likely to enhance falls self-efficacy, movement confidence, and balance control. In turn, enhanced beliefs efficacy should maximize intervention outcomes such as fear of falling. Indeed, previous Tai Chi studies have demonstrated that movement-related self-efficacy could be improved through Tai Chi (Li, McAuley, Harmer, Duncan, & Chaumeton, 2001) and that improved self-efficacy was related to higher levels of program participation (Li, McAuley, et al., 2001) and physical functioning (Li, Harmer, et al., 2001). Therefore, from a clinical standpoint, it seems warranted to examine the extent to which falls efficacy plays a buffering role in the fear-of-falling and Tai Chi relationship and thereby increase the understanding of how efficacy beliefs operate in the regulation of reductions in fear of falling. On the basis of this line of reasoning, we hypothesized that older adults whose falls self-efficacy improved over the course of a Tai Chi intervention would be most likely to benefit optimally with respect to reductions in fear of falling. To test this hypothesis, we operationalized falls self-efficacy as a mediator of the intervention effect on the fear-of-falling outcome. Unlike most other studies on fear of falling, in our study we operationalized fear of falling through the SAFFE measure (Lachman et al., 1998) as our intervention outcome.
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METHODS |
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and briefly summarize them here. The study was directed at an adult population aged 70 years and older, sampled from a patient database in the Legacy Health System in Portland, Oregon. The study was a randomized, controlled trial with parallel group design. Participants were randomly assigned to receive either a Tai Chi or a stretching control exercise condition, and they participated in a 60-min exercise session three times per week for 26 consecutive weeks (6 months). We assessed the outcome measure of fear of falling and the mediator measure of falls self-efficacy at baseline, at 3 months, and at the 6-month termination of the intervention. We conducted the intervention from March 2001 to May 2002. The institutional review boards of the Oregon Research Institute and the Legacy Health System approved the study protocol, and we obtained written informed consent from all participants.
Study eligibility criteria included the following: being 70 years of age or older; being inactive (defined as not being involved in any moderate or strenuous activity in the previous 3 months); being an independent ambulator not fully dependent on an assistive device; being free of chronic medical problems (e.g., severe neurological or orthopedic diseases, mobility impairment, or terminal illness) that would limit participation in low-to-moderate intensity exercise; having a physician's clearance to participate; and having no indication of significant cognitive impairment as indicated by a cutoff score of 3 on the Pfeiffer Mental Status Questionnaire (Pfeiffer, 1975).
From the initial available pool of 2,308 patients in the database, 669 individuals met the age requirement and were subsequently screened for eligibility. As part of our recruitment protocol, elderly patients received a letter signed by their primary care physician explaining that a study of the health status of older adults was being conducted and that they would be contacted by phone to determine if they would be willing to participate. Within a 2-week interval following the initial mailing, research staff made an initial follow-up phone contact and screened potential participants to establish their interest in and eligibility for the study. Those who met the study criteria and agreed to participate (N = 256) were scheduled for a baseline assessment. Participants then underwent baseline assessments, after which they were randomized to either a Tai Chi or a stretching control condition.
Intervention
Tai Chi
The Tai Chi classes were taught by experienced Tai Chi instructors who followed the classical 24-Form Yang style (China National Sports Commission, 1983), which emphasizes multidirectional weight shifting, awareness of body alignment, and multisegmental (arms, legs, trunk) movement coordination. Synchronized breathing (aligned with each Tai Chi movement) was also emphasized and integrated into the Tai Chi movement routine. Each session included 5–10 min of warm-up, approximately 45 min of Tai Chi practice, and 5–10 min of cool-down. Instruction covered learning new movements and reviewing movements learned in previous sessions. Each class practice session included musical accompaniment.
Stretching control
This program consisted predominantly of seated exercises, comprising stretches, controlled breathing, and relaxation. Our rationale for designing this condition was to provide participants with a structured, low-intensity exercise program that would contain comparable social interaction and enjoyment without providing the lower-extremity strength and balance training benefits of Tai Chi. The weekly class schedule and class format were identical to that of Tai Chi.
Measures
Outcome variable
Fear of falling was the primary outcome variable in this study, and we measured it by using the SAFFE (Lachman et al., 1998). The SAFFE contains 11 activities representing activities of daily living (ADLs) and instrumental ADLs (IADLs; e.g., taking a tub bath or shower), mobility (e.g., walking for exercise), and social activities (e.g., visiting friends or relatives). For each activity, several questions are asked: (a) "Do you currently do it?"; (b) "If you do the activity, how worried are you that you might fall?"; (c) "If you do not do the activity, do you not do it because you are worried that you might fall?"; (d) "If you do not do the activity because of worry, are there also other reasons that you do not do it?"; and (e) "If you are not worried, what are the reasons that you do not do it?" The SAFFE contains two indicators: (a) fear of falling, and (b) levels of activity. We did not use the latter indicator in the current study.
Li, McAuley, and colleagues (2002) showed that fear of falling (defined by the SAFFE) and falls efficacy (defined by the Activities-Specific Balance Confidence scale, or ABC scale, described in the paragraphs that follow) were two related but not isomorphic constructs, suggesting that SAFFE is a distinct fear-of-falling construct in measuring fear related to falls. In that study, Li and colleagues showed that the SAFFE was negatively associated with falls self-efficacy (i.e., lower levels of fear of falling were significantly related to higher levels of falls self-efficacy). The SAFFE has shown adequate validity and reliability (Lachman et al., 1998; Li, McAuley, et al., 2002; Li et al., 2003). We computed a total SAFFE fear-of-falling score by averaging item responses (ranging from 0 = not at all worried to 3 = very worried), with higher scores indicating greater fear of falling (Lachman et al., 1998). Cronbach alphas for this measure ranged from.65 to.70 across the three measurement waves.
Mediator variable
We defined and operationalized the falls efficacy mediator by the ABC scale (Powell & Myers, 1995). In our analyses, the mediator was operationalized in accordance with the operational framework described by Kraemer and colleagues (2002), in which a mediator is defined in terms of temporal relation to intervention onset and correlation with intervention choice (described in detail in the data analyses section).
The ABC is based on the self-efficacy framework (Bandura, 1986) and is an extension of the Falls Efficacy Scale (FES; Tinetti et al., 1990). The 16-item ABC scale assesses one's confidence in performing various ADLs without compromising one's balance. The scale has established psychometric properties with adequate internal, convergent, and construct reliability (Powell & Myers, 1995). In addition, the ABC scale taps a broader continuum of activity difficulty than does the FES, including such items as picking up an object from the floor, standing on a chair to reach for something, and walking on icy sidewalks. In this study, the ABC scale was rated by participants on a scale of 1, not at all confident, to 10, completely confident. (The original ABC scale was measured on a 0–100% response continuum. A pilot testing of the scale, n = 23, indicated that some participants had difficulty in accurately rating the scale based on a percentage rating. On the basis of the feedback of the pilot, the rating was changed from 1 to 10 as reported in this study.)
We computed the ABC scale score as the average level of confidence participants had across all 16 activities, ranging from 1 to 10, with higher scores indicating greater falls efficacy. Cronbach alphas for this measure ranged from.87 to.92 across the three measurement waves.
Data Analyses
We conducted the overall analyses on an intention-to-treat basis, so that all participants were included according to original treatment assignment and analyzed regardless of adherence to treatment or dropout status. We handled incomplete data resulting from premature intervention dropouts through the last-observation-carried-forward method (Peduzzi, Henderson, Hartigan, & Lavori, 2002).
We performed the overall study analyses in two stages. In Stage 1, we examined change in the mediating and outcome variables with respect to intervention condition (coded as 1 = Tai Chi, 0 = stretching control) through repeated measures analysis of variance (ANOVA). Establishing change in falls self-efficacy is an important initial step before its role as a mediator can be considered. In Stage 2, we analyzed the mediational effect by examining the treatment interaction effect (i.e., Condition x Mediator x Time), where we operationalized the mediator as a dichotomized variable named "improvement status," with 1 (improved) and 0 (not improved), using the ABC slope scores. We calculated the slope scores by the method of ordinary least squares (OLS) regression analysis. Regardless of intervention condition assignment, participants who showed a positive change (positive slope) in falls self-efficacy over the course of intervention were classified as the "improved" group, whereas participants who showed no improvements were classified as the "not improved" group. We included this mediator variable both as a main effect and as an interaction term in our three-factor (Condition, Improvement Status, and Time) repeated measures ANOVA model. With this design, a significant Condition x Improvement status x Time interaction effect indicates a mediational effect on the trajectory (or change) of fear-of-falling response. We carried out the follow-up within-group comparison by using a Bonferroni corrected p value of.005 (.05/11); we maintained this probability of Type I error at.005 for all subsequent mediational analyses.
With the exception of OLS regression, which we analyzed by using SAS (SAS Institute Inc., 1996), we conducted all statistical analyses by using SPSS (SPSS Inc., 1990). Where appropriate, we present effect size (d), computed as the mean difference between the two conditions divided by the pooled standard deviation, for the falls self-efficacy and fear-of-falling variables based on intervention assignment and subgroups (i.e., improved vs not improved).
Sample size and power
We made sample size determination and power calculations on the basis of the primary aim of the original study (Li et al., in press), which was targeted to detect a significant between-group difference on the primary outcome of fall frequency, with a planned sample size of 130 in each condition. Examination of the relationship between fear of falling and falls self-efficacy was specified in the original study plan as a secondary research question (or subgroup hypothesis). However, because it was a secondary outcome, no power calculations were made.
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RESULTS |
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Intervention Participation Status
Thirty-four randomized participants withdrew from the study at the study onset (no-shows). This left a total of 222 class-attending study participants. Of these participants, 47 (21%) withdrew (n = 24 in Tai Chi, n = 23 in control) during the entire intervention period. The overall dropout rate during the 6-month intervention was 21% (Tai Chi, 24 of 115; control, 23 of 107) excluding no-shows (n = 34). We found no statistical differences in the aforementioned baseline variables, including fear of falling and falls self-efficacy, between those who attended intervention classes (n = 222) and those who did not attend (n = 34). Similarly, we found no statistical differences between dropout participants (n = 47) and the remaining participants (n = 175).
Change in the Mediator of Falls Self-Efficacy
We observed a significant Condition x Time interaction effect, F(2, 253) = 37.16, p <.001, for the mediator of falls self-efficacy. Mean and standard deviation of falls self-efficacy are presented in Table 1. An additional analysis of preintervention to postintervention change scores on this variable indicated that the Tai Chi condition showed greater change (i.e., improvements in falls efficacy scores) compared with the stretching control condition (p <.001). Specifically, Tai Chi participants reported increased levels of falls efficacy compared with the stretching controls over the 26-week intervention period. We observed a relatively large effect size for this outcome (d =.79).
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Mediational Effect of Falls Self-Efficacy on Fear of Falling
Individual slope scores of the ABC measure, calculated by OLS, showed a mean slope score of.302 (SD =.50). By selecting positive slope scores (i.e., change in the ABC), we assigned 57% (n = 147) of the participants to the "improved" group (Tai Chi = 89, stretching = 58; slope score M =.59, SD =.46); we assigned the remaining 43% (n = 109) of the study participants to the "not improved" group. (Tai Chi = 36, stretching = 73; slope score M = –.09, SD =.18; the negative mean value indicates that individuals in this group had a negative slope, i.e., no improvement, on this measure.)
The repeated measures ANOVA revealed a significant Condition x Mediator x Time interaction effect, F(2, 251) = 10.735, p <.001. The results indicate that the greatest reductions in fear of falling occurred among participants in the Tai Chi condition who were in the "improved" (falls efficacy) subgroup. The intervention effects on fear of falling by the level of the falls efficacy mediator variable (improved vs not improved) are plotted in Figure 1. With respect to within-group differences on SAFFE scores, for those in the "improved" group, Tai Chi participants showed significantly lower fear-of-falling scores, F(2, 144) = 20.707, p <.001, compared with those in the stretching control. We observed no significant difference in fear of falling within the "not improved" group by study condition, F(2, 106) =.02, p =.98 (see Figure 1). With respect to the effect size in the "improved" group, the large effect observed in the overall intervention analysis remained for the falls self-efficacy measure (d =.73). We observed a medium effect size (per Cohen's criteria, 1988) for the fear-of-falling measure (d =.50).
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DISCUSSION |
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). In this study, we explored one mechanism—falls self-efficacy—that was hypothesized a priori to underlie change in the Tai Chi exercise and fear-of-falling relationship. Our analyses of intention-to-treat results provide empirical support for the mediational hypothesis, showing that improvements in falls efficacy were at least partially responsible for reductions in fear of falling observed in a 6-month Tai Chi intervention trial. Specifically, we found that, although there was an overall intervention effect on reductions in fear of falling for the Tai Chi condition, effects of intervention were stronger for those reporting improvements in falls efficacy compared with those with no improvements in falls efficacy. As shown in our data, not every participant in the Tai Chi condition showed improvements in falls efficacy. About 29% of Tai Chi participants (n = 36) reported no improvements in falls efficacy. Similarly, not every participant in the stretching control condition showed decreases in falls efficacy. About 44% of stretching control participants (n = 58) reported improvements in falls efficacy. However, a closer examination of these subgroups of individuals indicated that only those Tai Chi participants who reported improved falls efficacy were able to experience reductions in their levels of fear of falling, whereas those reporting improved falls efficacy in the stretching control did not. This finding suggests that it was the improvements in falls efficacy through Tai Chi that lead to the decrease in fear of falling. This supports our hypothesis that falls efficacy was a mediator of change in fear of falling resulting from Tai Chi. The effect size for the mean change scores in fear of falling observed between those who improved falls efficacy in the Tai Chi condition and those who did not improve represents a clinically significant effect.
Results from the current study are in line with other studies (Li, Harmer, et al., 2001; Li, McAuley, et al., 2001) that show that self-efficacy can be enhanced through Tai Chi. However, the current study extends these earlier studies (Li et al., in press; Li, Harmer, et al., 2001; Li, McAuley, et al., 2001) by examining the role of self-efficacy as a mechanism underlying the Tai Chi intervention effect in reducing fear of falling in older adults. We found that Tai Chi training per se did not necessarily result in reductions in fear of falling in all participants in that condition; rather, it was improvements in falls efficacy that operated as a mechanism leading to the decrease in fear of falling. In this respect, the findings of the current study are consistent with social cognitive theory (Bandura, 1986, 1997) and with our study hypothesis that falls self-efficacy plays a significant mediating role in the exercise and fear of falling relationship. Clearly, the practice of Tai Chi has provided participants with optimally challenging exercise tasks (e.g., single-limb balancing, weight shifting, hand–eye coordination, and postural control, which are beneficial to balance and strength gains), the successful completion of which resulted in positive gains in falls self-efficacy as evidenced by the ABC measure. In addition, given Bandura's (1997) position that more task-specific measurements of efficacy should result in more precise predictions of outcome, the correspondence between the item content of the ABC scale and the SAFFE scale appears to have maximized this relationship.
Implications
Findings from this study have important practical and research implications. First, there is evidence in the behavioral science literature that individuals benefit differently from a given preventive intervention (Brown & Liao, 1999; Ialongo et al., 1999; Kellam et al., 1991). Thus, determining the rate of improvement, or lack thereof, becomes an important enterprise in intervention research (Li, Fisher, et al., 2002). In this respect, intervention researchers need to consider mechanisms that underlie change in intervention outcomes (Kraemer et al., 2002). It is important to note that, had we not conducted the current analyses, the mediation of the Tai Chi and fear of falling relationship by falls efficacy would have been overlooked. Through a secondary analysis of a fear-of-falling outcome from a previous randomized controlled trial, we revealed a critical mediator of change that indicates that Tai Chi-induced improvements in falls efficacy are indeed an underlying mechanism in the Tai Chi and fear of falling relationship.
Second, the finding suggests that improvements in efficacy beliefs about capability and confidence in engaging in regular physical activities and functional tasks resulting from Tai Chi may be effective in reducing fears related to falling or losing balance. From a practical standpoint, the finding suggests that, to prevent or reduce fear of falling among older adults, an effective Tai Chi training protocol may be one that combines physical and mental training strategies designed to maximize beliefs regarding the control of functional mobility and balance-related tasks. Tai Chi may thus be considered a therapeutic exercise to build falls confidence in the face of declining functional and cognitive abilities among older adults and to counteract fears about losing balance or falling.
Third, the moderate effect size observed for the mediation effect suggests that the role of falls efficacy in reducing fear of falling should be considered in future studies that seek to evaluate the mechanisms of change in falls intervention outcomes. In this respect, Kraemer and colleagues (2002) have pointed out that any strong mediator should be considered in restructuring interventions for future evaluations. From the intervention perspective, future Tai Chi studies designed for falls reduction and balance improvements may consider falls efficacy as an intervention process variable through which to influence intervention endpoints (e.g., functional balance, falls, or injuries from falling). From a research design perspective, this suggests that future Tai Chi studies should have adequate sample sizes and preplanned power to formally evaluate the mediational hypothesis of falls efficacy on intervention outcomes.
Finally, the ABC scale may be less optimal for the assessment of tasks with incremental levels of difficulty. Bandura (1997, 2004) has recommended that self-efficacy beliefs be measured against gradated challenges to successful performance. Therefore, future studies should perhaps use falls efficacy measures that ask participants to indicate whether or not they can execute behavioral or functional movement tasks of increasing complexity or demand and gauge the extent to which they are confident of successfully doing so (McAuley & Mihalko, 1998).
Study Limitations
The current study findings should be interpreted in light of several limitations. First, the study only explored one possible mechanism—falls self-efficacy—in explaining reductions in fear of falling resulting from Tai Chi intervention. There may be other underlying mechanisms operating to influence the Tai Chi and fear-of-falling relationship. A previous study (Li, Fisher, et al., 2002) indicated that levels of physical function prior to intervention may be a moderator of Tai Chi benefits. Similarly, frequency of activity participation may serve as another potential mediator of reductions in fear of falling; however, we did not explore this in the current study. Therefore, further efforts are needed to identify other possible mechanisms influencing Tai Chi intervention outcomes with respect to fear of falling. Second, although we drew the sample from a physically inactive older population, the participants enrolled in the study were reasonably healthy. Further studies should confirm whether the demonstrated mediational role of self-efficacy between Tai Chi intervention and fear-of-falling outcomes remains robust in frail elders with functional deficits or limitations (i.e., limited in ADLs, IADLs, or both).
In addition, as indicated previously, the use of the ABC scale as a single measure of falls efficacy in this study is not without limitations. The ABC scale is generally considered to have greater sensitivity for older adults who have higher physical functioning than assessed by the FES (Powell & Myers, 1995). Increased sensitivity in a measure is certainly a strength and better captures, in a public health sense, more meaningful variation. However, its use in our relatively healthy sample may not have captured the potential role of falls efficacy in its relation to fear of falling in a physically vulnerable or frail population (e.g., elderly nursing home residents) who are at greater risk for falls and fear of falling. Furthermore, the ABC scale focuses on assessing one's confidence in performing the various activities "without losing balance or becoming unsteady." Therefore, the current study may only tap into the balance dimension of self-efficacy perceptions and not into efficacy beliefs with respect to the performance of activities "without falling."
In conclusion, in our present study we explored the mediational role of falls self-efficacy in the Tai Chi exercise and fear of falling relationship. We found support for the proposition that participants in Tai Chi who evidenced improvement in falls self-efficacy over the course of the intervention reported greater reductions in fear of falling compared with those who reported no or minimal change in falls efficacy. The findings from this study increase our understanding of the exercise (Tai Chi) and fear of falling relationship, and they underscore the important role of falls self-efficacy through exercise in the treatment of fear of falling in older adults. The results also suggest that exercise interventions targeted at reducing fall-related risks, such as fear of falling in older adults, should not overlook ways to enhance falls self-efficacy during the activity.
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Acknowledgments |
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Footnotes |
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Received for publication February 27, 2004. Accepted for publication June 3, 2004.
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