As many as one-third of community-living older individuals

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1 Validity of Divided Attention Tasks In Predicting Falls in Older Individuals: A Preliminary Study Joe Verghese, MD, MS,* Herman Buschke, MD,* Lisa Viola, DO,* Mindy Katz, MPH,* Charles Hall, PhD, Gail Kuslansky, PhD,* and Richard Lipton, MD* From the *Departments of Neurology and Epidemiology and Social Medicine, Albert Einstein College of Medicine, Bronx, New York; and IMR: A Division of Advanced PCS and the Center for Healthy Aging: Advanced PCS, Stamford, Connecticut. The Einstein Aging Study is supported by National Institute on Aging, National Institutes of Health Grant AGO3949. Presented in part at the 53rd annual meeting of the American Academy of Neurology, Philadelphia, Pennsylvania, May 9, Presented in part as thesis requirement for the Masters Degree in Clinical Research Methods, Albert Einstein College of Medicine, New York (JV). Address correspondence to Joe Verghese, MD, Einstein Aging Study, Albert Einstein College of Medicine, 1165 Morris Park Avenue, Room 338, Bronx, New York jverghes@aecom.yu.edu OBJECTIVES: Although cognitive impairment is known to be a major risk factor for falls in older individuals, the role of cognitive tests in predicting falls has not been established. Limited attentional resources may increase the risk for falls in older individuals. We examined the reliability and validity of divided attention tasks, walking while talking (WWT), in predicting falls. DESIGN: A prospective cohort study of 12-months duration. SETTING: Community-based longitudinal aging study, the Einstein Aging Study. PARTICIPANTS: Sixty nondemented community-living subjects, aged 65 to 98 (mean age standard deviation ). MEASUREMENTS: Simple and complex versions of the WWT task in addition to standard balance and cognitive assessments. The primary outcome was cumulative incidence of falls at 12 months. RESULTS: Thirteen subjects fell over the 12 months, four of whom had major injuries. The WWT task had good interrater reliability (r 0.602, P.001). Poor performance on simple (odds ratio (OR) 7.02, 95% confidence interval (CI) ) and complex WWT tasks (OR 13.7, 95% CI ) was highly predictive of falls. The simple task had a sensitivity of 46% and specificity of 89%. For the complex task, sensitivity was 39%, and specificity was 96%. CONCLUSIONS: The WWT is a reliable and valid test to identify older individuals at high risk for falls. Future studies with larger sample sizes and in different settings are needed to confirm the findings of this study. J Am Geriatr Soc 50: , Key words: divided attention; walking; older people; falls; screening As many as one-third of community-living older individuals fall every year, leading to loss of mobility, early institutionalization, and death. 1,2 Many medical and environmental risk factors have been identified for falls. 2,3 Recent guidelines on fall prevention recognize cognitive impairment as a leading risk factor for falls. 3 In the absence of previous studies, identification of specific cognitive processes most strongly associated with falls and optimal methods to assess and treat cognitive risk factors remain to be determined. Because individuals often engage in other activities while walking, walking in the real world involves divided attention. With aging or dementia, limited attentional resources may decrease the ability of older people to perform two or more simultaneous tasks, increasing the risk for falls. The multiplicity of risk factors makes it unlikely that a single screening test will identify all at-risk older people. Tinetti et al. showed that interventions based on specific mechanisms reduced rates of falls, highlighting the clinical relevance of the etiological heterogeneity of falls. 4,5 Identifying high-risk older people, as a prelude to intervention, is an important strategy. Previous studies have used various gait and mobility tests to predict falls. Some useful research procedures are complex or require specialized equipment and training, limiting their applicability to routine clinical practice. 3 7 Moreover, few tests have been prospectively validated, and none focus on the effect of cognitive impairment on falls. 3 8 Exploring the influence of cognitive processes on gait may help clarify a mechanism of falls and identify a subgroup of older individuals at risk. Divided attention tasks involving simultaneous performance of cognitive and manual tasks have been used to study attentional mechanisms. 9 Based on the hypothesis that limited attentional resources JAGS 50: , by the American Geriatrics Society /02/$15.00

2 JAGS SEPTEMBER 2002 VOL. 50, NO. 9 DIVIDED ATTENTION TASKS AND FALLS 1573 in older persons may increase risk for falls, we devised a divided attention task, walking while talking (WWT), to identify individuals at high risk for falls. The purpose of this preliminary study was to evaluate the validity of WWT tests in predicting falls in community-dwelling older individuals. METHODS Enrollment We enrolled 60 consecutive participants aged 65 and older from a community-based longitudinal aging study, the Einstein Aging Study (EAS). EAS participants were randomly recruited from Health Care Finance Administration population lists of Medicare recipients in the Bronx. EAS exclusion criteria include severe visual loss interfering with completion of neuropsychological tests, non-english or non-spanish speaking, and institutionalization. Subjects had to be healthy enough to make a clinic visit, but presence of medical illnesses was not used as an exclusion criterion. Details of medication use and medical illnesses, including presence or absence of various risk factors for falls, were prospectively collected from subjects at the time of enrollment with structured questionnaires. EAS subjects receive detailed neurological and neuropsychological evaluations at enrollment and annual follow-up visits. General cognitive status was assessed with the Blessed Information-Memory-Concentration test (BIMC). 10 None of the subjects in this study met dementia criteria of the Diagnostic and Statistical Manual of Mental Disorders, 4th Edition. Of the 60 subjects, 34 (57%) were women, and 22 (37%) lived alone. Seventeen subjects (28%) had had a fall in the year preceding enrollment, 12 (20%) reported neuropathy, and two (3%) had had previous strokes. Other reported risk factors for falls, such as foot deformities, use of prosthetic devices, depression, alcoholism, Parkinson s disease, or use of sedatives or antidepressant medications, were not present in our subjects when assessed at the baseline medical interview or clinical examination. Mobility Assessment Mobility and balance were assessed in all subjects in this study at enrollment using the following tests. Tinetti Balance and Mobility Scale The Tinetti balance and mobility scale (TBMS) was developed to screen for balance and mobility skills in older people and to determine risk for falls. 4,5 It uses nine tasks assessing mobility and balance in sitting and standing positions, generating scores from 0 to 16. The TBMS is sometimes combined with a gait assessment, not used herein, to improve assessment of fall risk. 5,6 Timed Gait The timed gait measures the time taken (in seconds) to walk 20 feet, turn, and return (40 feet total), at the subject s normal walking pace. Walking While Talking Tasks Subjects were timed walking the same course as the timed gait (40 feet), while reciting the letters of the alphabet aloud (WWT-simple). For the WWT-complex task, subjects recited alternate letters of the alphabet (a, c, e... ) while walking. The order of the WWT and TBMS tasks was randomly varied to avoid systematic bias. All subjects recited the alphabet in English, including five who were bilingual in English and Spanish. Interrater reliability for the WWT-simple was assessed in eight subjects, comparing evaluations performed by a neurologist and a neuropsychology assistant who were blinded to the study aims. Outcome and Follow-Up Cumulative incidence of falls at 12 months was the primary outcome. Falls were defined as sudden, unintentional, unprovoked changes in body posture resulting in the person being on a lower level, not due to a major intrinsic event (stroke) or overwhelming hazard. 5 Falls were classified as major if they resulted in injury. History of falls in the year preceding enrollment was obtained. To prospectively ascertain presence and circumstances of falls, research staff who were blinded to test performance conducted structured phone interviews with subjects at 6 and 12 months after enrollment. If subjects were unable to give precise date of fall, 1-week windows were used. Prospectively identified falls were reconfirmed with a significant other when available (one-third of subjects lived alone), with medical records, or at EAS follow-up visits. The subjects were reliable; all six subjects who reported falls at the 6-month interview recalled the fall at 12 months. Seven additional subjects reported a fall at 12 months, but not at 6 months. Statistical Analysis Chi-square tests were used to compare categorical variables, with Fisher exact tests applied as appropriate. Mann-Whitney U tests and independent-samples t tests were used for continuous variables. All tests were twotailed, with a criterion level of.05. Validity was compared by computing sensitivity, specificity, and positive predictive value (PPV) for the tests. (Sensitivity is the proportion of individuals with falls who have a positive test result. Specificity is the proportion of individuals without falls that have a negative test result. Positive predictive value is the proportion of individuals who have a positive test result and have the disease.) Because of our small sample, we used an a priori strategy to identify a subgroup of individuals with poor WWT performance that would be large enough for statistical analysis. Cutoff test scores were chosen at one standard deviation from the group mean. Resultant scores were 18 seconds or longer for timed gait (mean standard deviation ), 20 seconds or longer for WWT-simple (16.3 4), 33 seconds or longer for WWT-complex ( ), and 10 or fewer points for the TBMS ( ). To assess the influence of this choice, we performed post hoc analyses to examine a range of cutoff scores on these tests identified by receiver operating characteristic (ROC) techniques. Odds ratios (ORs) with 95% confidence intervals (CIs) were computed to study association between tests and falls. Survival analysis for WWT tests at selected cutoff scores was performed using the Kaplan-Meier method, and survival curves compared using log rank tests. Subjects were censored when they fell or when they completed the 12-month follow-up.

3 1574 VERGHESE ET AL. SEPTEMBER 2002 VOL. 50, NO. 9 JAGS RESULTS Baseline There were no significant differences in sex (58.8% vs 55.8% women) or living arrangement (47% vs 33% living alone) between the 17 subjects with a history of falls in the year preceding enrollment and the 43 subjects without falls. Subjects with previous falls were slightly older ( vs , P.07) and had higher BIMC scores ( vs , P.02). Older people with neuropathy were more likely to have had falls in the year before enrollment (47% vs 9%, P.002). Older people with previous falls walked more slowly at baseline ( vs seconds, P.002). They took longer to complete the WWT-simple ( vs seconds, P.002) and the WWT-complex ( vs seconds, P.001) and had lower scores on the TBMS ( vs , P.001). Follow-Up One subject died during the follow-up period and was excluded from the univariate but not the survival analysis. Of the remaining 59 subjects, six (10.2%) fell by 6 months and 13 (22%) by 12 months. Environmental hazards, such as uneven flooring or icy pavements, were cited as the cause of falls in most cases (62%). Seven falls (54%) occurred at home. Four (31%) falls were major, resulting in fractures of the pelvis (n 1) and foot (n 1) and extensive bruising (n 2). Two subjects had syncopal episodes not recorded as falls. Table 1 shows that there were no significant differences in age, sex, or self-reported height between fallers and nonfallers. Older people with neuropathy did not have more prospectively identified falls. Fallers had higher baseline BIMC scores ( vs , P.06) and walked slower at baseline and during WWT tasks. Baseline TBMS scores were not significantly different (P.06). Interrater Reliability There was good correlation (r 0.602, P.001) between the assessments done by the clinician and an independent neuropsychology assistant on the WWT-simple test. Validity Baseline walking speed had good specificity (84.7%) but modest sensitivity (38.4%) and PPV (41.7%). WWT-complex had the highest specificity (95.6%) but modest sensitivity (38.5%) at the selected cutoff scores (Table 2). WWT-simple had better sensitivity (46.1%) but lower specificity (89.4%) and PPV (54.5%). The TBMS had modest sensitivity (61.5%) and specificity (69.5%) but poor PPV (36.4%). Validity varies as a function of the cutoff score; for instance, selecting extreme scores ( 26 seconds) on WWT-complex improves sensitivity (54%) at the expense of specificity (85%). Table 2 presents validity of a range of cutoff scores identified by the ROC technique. We assessed baseline WWT performance as a predictor of falls over 12 months. Poor performance on WWT-simple (OR 7.02, 95% CI ) and WWT-complex tasks (OR 13.7, 95% CI ) was strongly predictive of falls. Kaplan-Meier plots of the WWT-simple (Figure 1) and WWT-complex (Figure 2) show significant separation by the end of the study (P.001). Fifty-five percent of subjects failing the WWT-simple fell, compared with the 15% of older people who did not exceed this score. Of subjects scoring over the cutoff on the WWT-complex, 71% fell, compared with 15% of controls. Clinical Observations All subjects completed the WWT tasks. The subjects found the instructions easy to follow. In general, all subjects slowed down while doing the WWT task, especially the complex version. No one fell during the task. Four subjects stopped walking during the WWT-complex of whom three fell. Many subjects who slowed down were also noted to make errors in reciting alternate alphabets. DISCUSSION Our preliminary study shows that WWT tests combining cognitive and gait tasks powerfully predict falls in nondemented, community-living older people. There were striking mean differences between older subjects who did and did not have prospectively identified falls in baseline walking time and in the performance of WWT tasks. In con- Table 1. Comparison of Baseline Characteristics in Prospectively Identified Older Subjects with and without Falls over 12 Months Variable Fallers (n 13) Nonfallers (n 46) P-value Age, mean SD Female, n (%) 9 (69.2) 25 (54.3).5 Height, inches, mean SD Neuropathy, n (%) 3 (23) 8 (17.4).7 Prior falls at baseline, n (%) 9 (69.2) 7 (15.2).001 BIMC score at entry, mean SD * Timed gait (40 feet), sec, mean SD * WWT-simple time, sec, mean SD * WWT-complex time, sec, mean SD * TBMS, points, mean SD * *Mann-Whitney U test. BIMC: Blessed Information-Memory-Concentration test (worst score 32); WWT: walking while talking test; TBMS: Tinetti balance and mobility scale (range 0 16).

4 JAGS SEPTEMBER 2002 VOL. 50, NO. 9 DIVIDED ATTENTION TASKS AND FALLS 1575 Table 2. Validity of Timed Gait, Tinetti Balance and Mobility Scale (TBMS), Walking While Talking (WWT)-Simple, and WWT-Complex Tests for Identifying Falls at 12 Months for a Range of Scores Test Sensitivity Specificity Positive Predictive Value Odds Ratio (95% confidence interval) P-value TBMS ( ) ( ).7 10* ( ).055 Timed gait 12 sec ( ).1 14 sec ( ).1 18 sec* ( ).057 WWT-simple 16 sec ( ) sec ( ) sec* ( ).009 WWT-complex 26 sec ( ) sec ( ) sec* ( ).001 *Preselected cutoff score. trast, performance on cognitive (BIMC) and balance (TBMS) tasks did not show significant group differences at baseline. The TBMS had higher sensitivity but lower specificity than either form of WWT in our sample. A previous study reported a sensitivity:specificity ratio of 70:52 for the combined Tinetti gait and balance scale in predicting falls over a year in 225 community-living older people. 6 Prior research on cognitive/motor tasks and falls is sparse. Shumway-Cook et al. reported that adding a cognitive task (counting backwards by three) to a balance assessment (timed up-and-go test) did not improve the ability to identify fallers at cross-section. 8 A direct comparison with our study is not possible because of the differences in study designs and tests. A recent functional imaging study reported that total brain activation measured during a dual task was significantly less than the sum of activation when the tasks were performed individually, suggesting a biological limit to the total activation possible at a given time. 11 Hence, walking while talking may limit resources available for either activity. Over a year, poor performance on the WWT-simple captured 55% of falls with high specificity (89%). Of the seven high-risk older people identified by WWT-complex, five fell in the following year. The progressive increase in PPV, from 42% for timed gait (OR 4.3) to 55% for WWT-simple (OR 7), and 71% for WWT-complex Figure 1. Kaplan-Meier survival plot for the probability of not having had a fall after 1 year (52 weeks) based on performance on the walking while talking (WWT)-simple task. The cutoff score was 20 seconds or longer (see Methods). Figure 2. Kaplan-Meier survival plot for the probability of not having had a fall after 1 year (52 weeks) based on performance on the walking while talking (WWT)-complex task. The cutoff score was 33 seconds or longer (see Methods).

5 1576 VERGHESE ET AL. SEPTEMBER 2002 VOL. 50, NO. 9 JAGS (OR 13.7), demonstrates the incremental validity of WWT tests over timed gait. These findings suggest that the processes involved by the WWT are etiologically relevant in the causation of falls. Both WWT tests identified high-risk groups for possible intervention. Because falls are etiologically heterogeneous, modest sensitivity is expected. The WWT tests are unlikely to identify people who fall because of unrelated mechanisms. Limitations mainly relate to the preliminary nature of our study. Our findings need to be validated by future studies with larger samples and in other settings. A higher fall rate will be expected in nursing homes or clinics. The cutoff scores were chosen to optimally differentiate performance stratified by fall risk, and the values need to be validated in larger samples. Our post hoc analysis shows that changing scores alters test characteristics. The WWT cutoff scores reflect the nature of our sample, and different scores and distances might be used and validated in other settings. We had a lower incidence of falls than previous studies, which have used fall diaries and mail-back monthly postcard calendars. 5 Even in these studies, recall bias is a problem because cognitively impaired older people may underreport falls. Our nondemented subjects had minimal recall bias, as suggested by the correspondence between the 6- and 12-month falls data. Our small sample did not include older people with dementia, who have a higher rate of falls and more difficulty completing dual tasks. 3,9,12 Six subjects had mild cognitive abnormalities as defined by a BIMC score of 6 or higher. Subjects who fell had nonsignificantly higher BIMC scores (P.08). This study focused on the influence of the cognitive task on gait and not the effect of gait on the cognitive task. Previous studies and our own observations indicate that the simultaneous performance of two tasks leads to deterioration in both subtasks. 9,11,12 Nursing home residents who stopped to talk were reported to have more falls. 13 It may be useful to include qualitative differences in task performance in future refinements of the WWT. This is the first study to show that performance on divided attention tasks can predict falls in older people. Our intention was not to replace current screening tests such as the TBMS but to extend the scope of current fall assessments by adding cognitive parameters. 3 For instance, combining the TBMS with WWT-simple improves the sensitivity to 71% with fair specificity (70%). Future strategies in clinical or community settings might include fall questionnaires to detect at-risk older people with previous falls or a history of dementia followed by cognitive (WWT) or balance tests (TBMS) to identify modifiable risk factors. The WWT offers the chance to introduce specific interventions such as cognitive rehabilitation or pharmacological treatments. WWT tasks are simple, reliable, and take less than a minute to perform. If our results are confirmed, WWT tasks can be easily incorporated into standard clinical examinations to identify older people at high risk for falls. REFERENCES 1. Sattin RW. Falls among older persons: A public health perspective. Annu Rev Public Health 1992;13: Tinetti M, Speechley M, Ginter S. Risk factors for falls among elderly persons living in the community. N Engl J Med 1988;319: American Geriatrics Society, British Geriatrics Society, and American Academy of Orthopedic Surgeons Panel on Falls Prevention. Guideline for the prevention of falls in older persons. J Am Geriatr Soc 2001;49: Tinetti ME, Williams TF, Mayeweski R. A fall risk index for elderly patients based on number of chronic diseases. Am J Med 1986;80: Tinetti ME, Baker DI, McAvay G et al. 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