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Middle-old and old-old retirement dwelling adults respond differently to locomotor challenges in cluttered environments
Gait & Posture 23 (2006) 486–491 www.elsevier.com/locate/gaitpost
Middle-old and old-old retirement dwelling adults respond differently to locomotor challenges in cluttered environments Rebecca J. Reed, Catherine R. Lowrey, Lori Ann Vallis * Department of Human Health and Nutritional Sciences, College of Biological Science, University of Guelph, Animal Science/Nutrition Building, Guelph, Ont., Canada N1G 2W1 Received 16 April 2004; received in revised form 5 April 2005; accepted 12 June 2005
Abstract Obstacle navigation during locomotion was investigated in older adults using an obstacle course paradigm under different ambient lighting conditions. Similar strategies for obstacle navigation were observed between the two age groups studied (middle-old: 75–85 years and old-old adults: 85 years and older), however old-old individuals were ‘‘less’’ successful at avoiding obstacles. Differences observed between the two age groups in obstacle course performance may be attributed to changes in spatial reference frames that occur with age and/or differences in perceived threat of obstacles in the travel path. Reduced lighting conditions and increasing age were also found to have significant affects on obstacle navigation. # 2005 Elsevier B.V. All rights reserved. Keywords: Older adults; Obstacle course navigation; Locomotion; Cluttered environments
1. Introduction Falls are the leading cause of fatal injury among Canadians over the age of 65 years [1]. Health Canada reported the cost of fall-related injuries to Canada’s Health Care system to be $2.8 billion a year, a figure that is expected to rise with the increasing number of seniors in Canada [2]. Accordingly, there has been an explosive amount of research conducted on the factors that affect instability during perturbed standing and mobility in older adults [3–6]. Literature in this area indicates that most falls occur during ambulation, especially within the home [7–9]. Furthermore, walking in low lighting conditions may increase the risk for falls in older adults [6]. Obstacle course paradigms have been used to investigate the mobility of persons with visual disorders [10,11] and community dwelling older males with a falls history (<85 years old [12]) but has yet to be applied to a general healthy older (>85 years) population residing in a supportive care facility. This is despite the fact that the incidence of falls * Corresponding author. Tel.: +1 519 824 4120; fax: +1 519 763 5902. E-mail address: [email protected] (L.A. Vallis). 0966-6362/$ – see front matter # 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.gaitpost.2005.06.010
causing injury is more frequent in institutional dwelling older adult populations compared to their home dwelling counterparts [13]. Obstacle course performance measures can identify individuals at risk of falling in an experimental paradigm that is reflective of the environmental hazards encountered during normal activities of daily living (ADLs). ADLs may involve avoiding obstacles such as a table in the hallway and stepping over a transition from carpet to floor and can provide greater detail about the gait and balance adaptations required for the challenges encountered in real life situations [12]. Insight into mobility changes that occur when less light is available (i.e. going to the bathroom at night with only a nightlight) could be obtained if navigating of an obstacle course was performed in this reduced lighting level. The purpose of the present study is to provide a preliminary investigation of older adult mobility using an obstacle course paradigm with ambient light changes and obstacles with varying contrasts. We hypothesized that with increased age, older adults will walk slower and contact more obstacles in the reduced light condition compared to the normal light condition. In addition, we expected a greater number of contacts with obstacles of low contrast compared to those of high contrast.
R.J. Reed et al. / Gait & Posture 23 (2006) 486–491
2. Methods 2.1. Participants Ten male and seven female healthy older adults aged 85.6 (5.2) years volunteered from a multi-care retirement facility in Guelph, Ontario. Experimental protocol was outlined and informed written consent was provided. Ethics approval was obtained through the Office of Research at the University of Guelph. Participants were pre-screened a few days prior to the testing protocol using clinical evaluations including the Timed Up and Go (TUG) [14], the Activities-specific Balance Confidence (ABC) scale [15] and a timed 10 m walk. In addition, a background medical and activity questionnaire was given to ensure the general good health of the participants. Participants were excluded from the study if they reported any vestibular loss, non-corrected visual impairment (e.g. cataracts) or any dizziness during ADLs. Participant characteristics and clinical test scores are presented in Table 1. 2.2. Obstacle course The obstacle course (Fig. 1) consisted of a grey carpeted walking area in a triangular orientation with three main straight sections, 5 m in length and 1.5 m in width. The triangular orientation was used in order to allow for continuous movement around the course with three different start points (numbered one, two and three), which facilitated randomization of the starting points. Obstacles were placed such that participants had to step over, duck under or step around to avoid making contact. There were three sections of the obstacle course: sections one and two consisted of three obstacles each (one of each
487
type) and section three consisted of six obstacles (two of each type). The obstacles were all white in section one, all black in section two. Section three consisted of three white and three black obstacles. The rationale for varying obstacle contrasts by sections was based on the hypothesis that participants would make less contact with obstacles of high contrast (white obstacles on grey carpet) versus low contrast (black obstacles on grey carpet) and that low contrast obstacles would be more difficult to avoid, especially in a reduced lighting environment [10,11]. The obstacles were constructed from foam making them durable and not harmful to the participants if contacted. The step obstacle was 6.5 cm high and 6.5 cm in width, the column obstacle for circumvention was 28 cm in circumference and 1 m high. The hanging obstacle for the ducking under task was 21 cm in circumference and was adjusted so it hung at nose height for each participant. Two ambient room lighting conditions were presented during the experimental protocol, a full overhead room lighting condition (NORM, 200 lux) and a low room lighting condition (LOW, 10 lux). The LOW lighting condition was achieved using ‘‘rope lights’’ generally used as a garden decoration, secured to the outside of the carpet path. 2.3. Experimental protocol Instructions were given to the participants to walk at their own comfortable pace and to try to avoid hitting or touching any of the obstacles. Participants were free to choose their own avoidance strategy. Starting positions were randomized for the two lighting blocks and initial lighting levels, NORM or LOW, were counterbalanced between the participants. Progression through the obstacle course was monitored with two main methods, timing and the number of obstacle contacts. Timing was recorded as an overall completion time
Table 1 Participant characteristics and clinical test scores Subject
Age (years)
Age group
Gender
TUG (s)
ABC average score (%)
10 m (s)
Inside
Outside
Reach
1 2 4 5 14 15 17
84 81 75 80 78 84 84
Middle-old Middle-old Middle-old Middle-old Middle-old Middle-old Middle-old
M M M M M M F
9.5 13.5 9.7 17.2 15.4 12.5 10.4
94.2 90.7 95.7 94.2 62.8 81.8 95.7
88 73 78 80 64 80 90
87.5 71.3 100.0 92.5 76.2 80.0 76.2
11.2 13.4 12.5 11.9 13.4 13.1 10.4
3 6 7 8 11 13 16 18 19 20
89 93 94 86 85 88 90 85 89 90
Old-old Old-old Old-old Old-old Old-old Old-old Old-old Old-old Old-old Old-old
M F F M F F F M M F
12.7 9.8 13.7 9.2 13.2 16.2 17.4 16.6 7.7 12.1
94.2 96.4 97.1 96.4 88.6 57.1 62.1 78.5 82.8 50.7
82 90 92 90 80 64 51 73 90 48
72.5 75.0 87.5 62.5 80.0 45.0 52.5 72.5 61.2 52.5
12.0 10.8 14.2 9.7 11.8 19.6 17.5 17.5 8.7 10.1
Note: Activities-specific Balance Confidence (ABC) scores are divided into three different task categories—inside, outside and reach activities.
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Fig. 1. Schematic diagram of the obstacle course. Dotted lines indicate rope lighting used during the LOW lighting condition. Sections one and two contained three obstacles each: a duck (suspended from ceiling), step and circumvent. Section three contained two obstacles of each type. Obstacle contrast was distributed with section one high contrast (white obstacles), section two low contrast (black obstacles) and section three mixed contrast (both black and white obstacles). Start sections indicate three start positions randomized throughout the trials.
of the three-section course circuit, and the type and location of obstacles contacted was recorded. The obstacle course was navigated starting at each section (one, two or three) four times for total of 12 trials in the NORM and 12 trials in the LOW light conditions. As the obstacle course contained a total of 12 obstacles, the maximum number of contacts possible was 144 (12 total obstacles per trial 12 trials) for each lighting condition. A 10 min rest break was scheduled during the change in light condition to reduce the effects of fatigue and allow for visual accommodation. Additional rest breaks were given throughout the protocol, or when the participant requested. 2.4. Data analysis Participants were grouped for all analyses into two age categories [16]: middle-old (age 75–84 years; n = 7) and old-old (age 85 years and over; n = 10). 2.4.1. Obstacle course performance The total number of obstacle contacts made by each participant during the obstacle course was calculated for both lighting conditions (maximum number of contacts possible, 144 in either condition). Separate two-tailed (a = 0.05) Mann–Whitney non-parametric analyses were conducted on the number of contacts made (dependant variable) with respect to lighting condition, obstacle contrast, sex and age (independent variables). 2.4.2. Timing Non-parametric statistical analyses, two-tailed (a = 0.05) Mann–Whitney and Wilcoxon Signed Ranks tests, were conducted to analyze the overall total time required by participants to complete the obstacle course. 2.4.3. Type of obstacle hit A mixed repeated measures model analysis of variance (ANOVA) with post hoc Bonferroni corrected paired t-tests (95%) was performed in order to determine if there were differences in the types of obstacles hit (dependant variable) between the two age groups and the two lighting conditions (independent variables).
2.4.4. Balance confidence and functional capabilities Clinical test scores on the ABC questionnaire were set as dependent variables in non-parametric methods of analysis. Each participant’s overall average score for confidence on the ABC activities were analyzed, separated as a function of activity type, outside, inside and reaching activities. The rationale for the separation of these activities from one another was that the average scores for each category would provide insight into the type of activities that would possibly be perceived as more challenging for one age group versus another. Functional capabilities were then assessed using a univariate ANOVA model of the Timed Up and Go scores related to the number of obstacle contacts and total time to complete the course. Finally, the 10 m walk times were analyzed using a non-parametric Mann–Whitney (a = 0.05) to determine whether any non-obstructed self-selected speed differences existed between the two age groups.
3. Results Self-reports of activities enjoyed on a daily basis revealed walking (100% middle-old, 70% old-old) to be the most frequent followed by participation in a half an hour fitness classes three times a week (71% middle-old, 40% old-old). Of the middle-old (n = 7) group, only 57% reported using a walking aide (cane) and 14% reported having experienced a fall within the last 2 years. A fall was defined as an unexpected movement by which the participant contacted a lower surface during a routine activity, and did not occur due to fainting or illness. Of the old-old group (n = 10), 40% reported using walking aides (cane) and 30% reported a fall within the last 2 years. Participants with walking aides reported that their use was restricted to outdoor walking, and therefore chose not to use their aide during the testing protocol. 3.1. Obstacle course performance Results of the individual non-parametric analyses indicated significant effects ( p < 0.05) between the total numbers of contacts made during obstacle course negotia-
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Fig. 2. Total number of obstacle contacts made (in brackets) by the middleold and old-old age groups in each lighting condition. The old-old group contacted significantly more obstacles (*p < 0.05) compared to the middleold group in both lighting conditions.
tion for three of the independent variables: lighting condition, age and sex. However, obstacle contrast was found to not significantly affect the number of obstacle contacts ( p = 0.591). Analyses of obstacle contacts, in each lighting condition by age, revealed an interesting finding, the old-old age group contacted significantly more obstacles than the middle-old group in both lighting conditions ( p < 0.05; Fig. 2). 3.2. Timing In general, all participants decreased the speed with which they completed the course in the LOW lighting condition (two-tailed significance, p < 0.001; Fig. 3). Mean time for course completion collapsed across age groups were 22.3 7.2 s in NORM and 25.6 7.6 s in LOW. 3.3. Type of obstacle hit A significant interaction was observed between the type of obstacle hit and the two age groups (F (2,10) = 4.148, p = 0.049). Further analysis revealed that the interaction involved the step and hanging obstacles (F (1,11) = 8.828, p = 0.013). Paired t-tests between the age groups for both
Fig. 3. Time (s) for completion of one circuit (three sections) of the obstacle course in the NORM (white) and LOW (shaded) lighting condition for both age categories. Both age groups significantly increased time for course completion in the LOW lighting condition.
Fig. 4. Number of obstacle contacts for the two lighting conditions NORM (white) and LOW (shaded). Significant differences ( p < 0.05) are indicated by (*) and trends are indicated by (^).
lighting conditions indicated that the old-old group tended to contact the hanging obstacle more often than the middle-old group ( p = 0.054), whilst the middle-old tended to contact the step more often ( p = 0.142). Within the old-old group, different responses to the types of obstacles contacted and two lighting conditions were observed. The hanging obstacle was contacted significantly more than the step ( p = 0.002) and column ( p = 0.042) obstacles. As well, more contacts of the column and hanging obstacles were made in the LOW light condition compared to the NORM light condition ( p = 0.026 and 0.005, respectively). Within the middle-old group, a more consistent number of contacts across the types of obstacles and lighting conditions was observed, with the exception of the column obstacle which they contacted significantly more often in the LOW lighting condition ( p = 0.045; Fig. 4). 3.4. Balance confidence and functional capabilities The categorical analysis for the inside, outside and reaching tasks contained in the ABC evaluation tool revealed no significant difference in confidence ratings for outside and inside activities between the age groups (twotailed significance, p = 0.759 and 0.706, respectively). A significantly different confidence rating was obtained for the reaching tasks (two-tailed significance, p = 0.033). Additionally, the TUG scores (mean scores 12.5 3.0 s for the middle-old and 12.9 3.3 s for the old-old group) and 10 m walk times (1.2 0.06 and 1.4 0.14 m/s for the middleold and old-old participants, respectively) revealed no significant differences in functional capabilities between the two age groups (F (1,13) = 0.080, p = 0.782 and two-tailed significance, p = 0.922). Thus, on a straight unobstructed walking path the old-old group was not significantly slower than the middle-old group.
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4. Discussion Participants were recruited from the same retirement facility to ensure homogeneity in their exercise and social environments as well as the mobility challenges encountered in their daily living environment (crowded dining hall, etc.). Comparison of mobility to a younger population was felt to be counterintuitive to the objectives of this study as responses to experimental protocol for a younger population might be different due to the nature of the aging process and/ or a dissimilar lifestyle or ADLs. 4.1. Functional capabilities and balance confidence Functional capabilities and balance confidence assessed using the TUG, 10 m walk and ABC tests were not significantly different between age groups, indicating that all participants were similar in mobility function and balance confidence. Differences in obstacle avoidance performance were therefore not directly related to balance confidence or functional abilities evaluated in this study. The only exception was in the reach category, however this finding was driven by the response to one question (standing on a chair and reaching) and therefore not relevant to our current research questions. 4.2. Obstacle avoidance strategies Avoidance strategies adopted by the middle-old and oldold groups were similar in several ways. In response to the LOW lighting condition, both the age groups adopted a decreased speed strategy. This particular strategy has been reported in related literature as a typical response to decreased ambient lighting during obstacle course navigation [11,17]. Decreased walking speed has been attributed to a more cautious gait pattern in order to reduce the risk of instability possibly resulting in a fall [6] and in response to obstacles along the travel path [18,19]. Although the old-old group adopted similar cautious strategies as the middle-old group, their ability to accommodate their locomotor patterns to the environment was less successful as they contacted significantly more obstacles compared to the middle-old group. The increased number of contacts in this age group may indicate that these individuals have mobility deficiencies and are at a higher risk for falling when navigating a cluttered environment, as most incidents of falls occur during ambulation [7–9]. Unexpectedly, the contrast of the obstacles did not have a significant effect on whether the obstacles were contacted. It was hypothesized that more contacts would occur with low contrast obstacles, as these obstacles are more difficult to see especially in the LOW lighting condition. Previous work has identified obstacle contrast as an important factor in obstacle navigation in support of the above hypothesis [11,17]; however, this hypothesis was not supported by the current work. More drastic changes in contrast, i.e. placing a black obstacle on a white carpet, may have yielded a contrast
effect; however, the current study used industrial grey carpet, commonly used in supportive care facilities. A significant gender difference was found for number of obstacles contacted. However, this may have been driven by an unequal division of gender between the two age groups (old-old: six females and four males; middle-old: six males and one female). Future investigations into possible gender differences are necessary to further explore this finding. 4.3. Type of obstacle contacted A possible explanation for the differences observed between the types of obstacles for the two age groups may be related to the spatial frame of reference used during the task. During locomotor tasks, allocentric and egocentric spatial frames of reference are used to navigate our environment [20,21]. Wu [5] reported age-related changes in the upper body orientation during perturbed standing and suspected that an egocentric head centred reference frame is not well stabilized in older adults compared to young adults. A rigid strategy where the head is stabilized on the trunk may be adopted in order to reduce the number of degrees of freedom that have to be controlled during complex intersegmental movements [22]. Adopting this posture could in fact lead to instability, as the head–trunk segmental unit may incur greater excursions of the center of mass (COM) during locomotion, reducing one’s tolerance to postural disturbances [5]. This strategy may further explain the increased incidence of unsuccessful ducking and circumvention manoeuvres observed in the old-old participants. Although Wu reported no significant differences in rigidity within the older age groups themselves, participants in this previous work are appreciably younger (oldest group, 73.5 2.0 years) than the present study (85.6 5.2 years). Changes in segmental control during locomotion may occur over the age of 85 years that are, as of yet, unknown. Further investigation into segmental co-ordination and locomotor control are necessary to identify age-related changes. This work will increase our understanding how these changes influence or impact the ability of older adults to navigate complex environments. Another explanation for the old-old group contacting the hanging versus stepping obstacle could be related to the perceived threat of the different obstacles. If the stepping task was indeed more threatening to this old-old group, their full attention might be focused on clearing the stepping obstacle task with the result of making more contacts with the hanging and column obstacles. The increased incidence of old-old adults contacting the hanging obstacle is of critical importance to these individuals as hanging obstacles could pose a safety threat to older an adult’s balance. Further complications such as loss of consciousness or the acquisition of a serious head injury may be added to the loss of postural stability. Avoidance of hanging obstacles is a task that is often encountered (i.e. ducking under an open cabinet). The increased number of obstacle contacts observed in the LOW light condition for both the age groups in
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comparison to the number of contacts made in the NORM light condition (Fig. 2) suggest an increased risk for loss of balance and perhaps falls in reduced lighting conditions. Such evidence is compelling as it suggests the importance of adequate ambient lighting conditions in retirement facilities for the prevention of falls in older adults. Previous studies have reported similar increases in falls risk during low light conditions [11]. Further research is currently under way in our laboratory to investigate the effects of ambient room lighting on locomotor behaviour and changes in the segmental coordination of older adults in cluttered environments.
5. Conclusion There is a limited amount of research investigating obstacle avoidance in older adults and none that looks specifically at a supportive care facility-dwelling population. Although our study is limited due to a small number of subjects, it outlines underlying relationships regarding obstacle navigation for this specific population. Perhaps a larger sample population would reveal significant results where trends were observed in the current work. Middle-old and old-old adults differed with respect to the number and type of obstacles contacted and both groups contacted more obstacles when lighting was reduced. We propose that these discrepancies may be related to different locomotor reference frames used by the two populations and/or a difference in the perceived postural threat of obstacles in their environment.
Acknowledgements Financial support was received from the University of Guelph (RJR and LAV). We acknowledge and would like to thank kinesiologists Jennifer Hartwick and Jennifer Perry, the management, support staff and residents of The Village of Riverside Glen, Guelph, Ont., as well as Oakwood Retirement Community Facilities.
References [1] Bloem B, Steijns J, Smits-Engelsman BC. An update of falls. Curr Opin Neurol 2003;16:15–25. [2] Health Canada. News Release.;http://www.hc-sc.gc.ca/english/media/ releases/2001/2001_78e.htm2001.
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[3] Maki BE. Gait changes in older adults: predictors of falls or indicators of fear. J Am Geriatric Soc 1997;45(3):313–20. [4] Lord SR, Clark RD, Webster IW. Postural stability and associated physiological factors in a population of aged persons. J Gerontol 1991;46:M69–76. [5] Wu G. Age-related differences in body segmental movement during perturbed stance in humans. Clin Biomech 1998;13:300–7. [6] Menz HB, Lord SR, Fitzpatrick RC. Age-related differences in walking stability. Age Ageing 2003;32:137–42. [7] Tinetti ME, Doucette J, Claus E, Marottoli R. Risk factors for serious injury during falls by older persons in the community. J Am Geriatric Soc 1995;43(11):1214–21. [8] Cali DM, Kiel DP. An epidemiologic study of fall-related fractures among institutionalized older people. J Am Geriatric Soc 1995;43(12):1336–40. [9] Norton R, Campbell AJ, Lee-Joe T, Robinson E, Butler M. Circumstances of falls resulting in hip fractures among old people. J Am Geriatric Soc 1997;45(9):1108–12. [10] Kuyk T, Elliot JL, Biehl J, Fuhr PS. Environmental variables and mobility performance in adults with low vision. J Am Optom Assoc 1996;67:403–9. [11] Kuyk T, Elliot JL, Fuhr PSW. Visual correlates of mobility in real world settings in older adults with low vision. Opt Vis Sci 1998;75(7):538–47. [12] Rubenstein LZ, Josephson KR, Trueblood PR, Yeung K, Harker JO, Robbins AS. The reliability and validity of an obstacle course as a measure of gait and balance in older adults. Aging Clin Exp Res 1997;9:127–35. [13] Luukinen H, Koski K, Honkanen R, Kivela S-L. Incidence of injurycausing falls among older adults by place of residence: a populationbased study. J Am Geriatric Soc 1995;43:871–6. [14] Shumway-Cooke A, Brauer S, Woollacott M. Predicting the probability for falls in community-dwelling older adults using the Timed Up & Go test. Phys Ther 2000;80(9):896–903. [15] Powell LE, Myers AM. The Activities-specific Balance Confidence (ABC) scale. J Gerontol 1995;50A:M28–34. [16] Atchley RC. Social forces and aging, 5th ed., Belmont, CA: Wadsworth Publishing Company, 1988. [17] Hassan SE, Lovie-Kitchin JE, Woods RL. Vision mobility performance of subjects with age-related macular degeneration. Optom Vis Sci 2002;79(11):697–707. [18] Patla AE, Prentice SD, Robinson C, Neufeld J. Visual control of locomotion: strategies for changing direction and for going over obstacles. J Exp Psychol 1991;17(3):603–34. [19] Vallis LA, McFadyen BJ. Locomotor adjustments for circumvention of an obstacle in the travel path. Exp Brain Res 2003;152:409– 14. [20] Hollands MA, Sorenson KL, Patla AE. Effects of head immobilization on the coordination and control of head and body reorientation and translation during steering. Exp Brain Res 2001;140:223– 33. [21] Colby CL. Action-oriented spatial reference frames in cortex. Neuron 1998;20:15–24. [22] Pozzo T, Berthoz A, Lefort L. Head stabilization during various locomotor tasks in humans. I. Normal subjects. Exp Brain Res 1990;82:97–106.
Middle-old and old-old retirement dwelling adults respond differently to locomotor challenges in cluttered environments Rebecca J. Reed, Catherine R. Lowrey, Lori Ann Vallis * Department of Human Health and Nutritional Sciences, College of Biological Science, University of Guelph, Animal Science/Nutrition Building, Guelph, Ont., Canada N1G 2W1 Received 16 April 2004; received in revised form 5 April 2005; accepted 12 June 2005
Abstract Obstacle navigation during locomotion was investigated in older adults using an obstacle course paradigm under different ambient lighting conditions. Similar strategies for obstacle navigation were observed between the two age groups studied (middle-old: 75–85 years and old-old adults: 85 years and older), however old-old individuals were ‘‘less’’ successful at avoiding obstacles. Differences observed between the two age groups in obstacle course performance may be attributed to changes in spatial reference frames that occur with age and/or differences in perceived threat of obstacles in the travel path. Reduced lighting conditions and increasing age were also found to have significant affects on obstacle navigation. # 2005 Elsevier B.V. All rights reserved. Keywords: Older adults; Obstacle course navigation; Locomotion; Cluttered environments
1. Introduction Falls are the leading cause of fatal injury among Canadians over the age of 65 years [1]. Health Canada reported the cost of fall-related injuries to Canada’s Health Care system to be $2.8 billion a year, a figure that is expected to rise with the increasing number of seniors in Canada [2]. Accordingly, there has been an explosive amount of research conducted on the factors that affect instability during perturbed standing and mobility in older adults [3–6]. Literature in this area indicates that most falls occur during ambulation, especially within the home [7–9]. Furthermore, walking in low lighting conditions may increase the risk for falls in older adults [6]. Obstacle course paradigms have been used to investigate the mobility of persons with visual disorders [10,11] and community dwelling older males with a falls history (<85 years old [12]) but has yet to be applied to a general healthy older (>85 years) population residing in a supportive care facility. This is despite the fact that the incidence of falls * Corresponding author. Tel.: +1 519 824 4120; fax: +1 519 763 5902. E-mail address: [email protected] (L.A. Vallis). 0966-6362/$ – see front matter # 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.gaitpost.2005.06.010
causing injury is more frequent in institutional dwelling older adult populations compared to their home dwelling counterparts [13]. Obstacle course performance measures can identify individuals at risk of falling in an experimental paradigm that is reflective of the environmental hazards encountered during normal activities of daily living (ADLs). ADLs may involve avoiding obstacles such as a table in the hallway and stepping over a transition from carpet to floor and can provide greater detail about the gait and balance adaptations required for the challenges encountered in real life situations [12]. Insight into mobility changes that occur when less light is available (i.e. going to the bathroom at night with only a nightlight) could be obtained if navigating of an obstacle course was performed in this reduced lighting level. The purpose of the present study is to provide a preliminary investigation of older adult mobility using an obstacle course paradigm with ambient light changes and obstacles with varying contrasts. We hypothesized that with increased age, older adults will walk slower and contact more obstacles in the reduced light condition compared to the normal light condition. In addition, we expected a greater number of contacts with obstacles of low contrast compared to those of high contrast.
R.J. Reed et al. / Gait & Posture 23 (2006) 486–491
2. Methods 2.1. Participants Ten male and seven female healthy older adults aged 85.6 (5.2) years volunteered from a multi-care retirement facility in Guelph, Ontario. Experimental protocol was outlined and informed written consent was provided. Ethics approval was obtained through the Office of Research at the University of Guelph. Participants were pre-screened a few days prior to the testing protocol using clinical evaluations including the Timed Up and Go (TUG) [14], the Activities-specific Balance Confidence (ABC) scale [15] and a timed 10 m walk. In addition, a background medical and activity questionnaire was given to ensure the general good health of the participants. Participants were excluded from the study if they reported any vestibular loss, non-corrected visual impairment (e.g. cataracts) or any dizziness during ADLs. Participant characteristics and clinical test scores are presented in Table 1. 2.2. Obstacle course The obstacle course (Fig. 1) consisted of a grey carpeted walking area in a triangular orientation with three main straight sections, 5 m in length and 1.5 m in width. The triangular orientation was used in order to allow for continuous movement around the course with three different start points (numbered one, two and three), which facilitated randomization of the starting points. Obstacles were placed such that participants had to step over, duck under or step around to avoid making contact. There were three sections of the obstacle course: sections one and two consisted of three obstacles each (one of each
487
type) and section three consisted of six obstacles (two of each type). The obstacles were all white in section one, all black in section two. Section three consisted of three white and three black obstacles. The rationale for varying obstacle contrasts by sections was based on the hypothesis that participants would make less contact with obstacles of high contrast (white obstacles on grey carpet) versus low contrast (black obstacles on grey carpet) and that low contrast obstacles would be more difficult to avoid, especially in a reduced lighting environment [10,11]. The obstacles were constructed from foam making them durable and not harmful to the participants if contacted. The step obstacle was 6.5 cm high and 6.5 cm in width, the column obstacle for circumvention was 28 cm in circumference and 1 m high. The hanging obstacle for the ducking under task was 21 cm in circumference and was adjusted so it hung at nose height for each participant. Two ambient room lighting conditions were presented during the experimental protocol, a full overhead room lighting condition (NORM, 200 lux) and a low room lighting condition (LOW, 10 lux). The LOW lighting condition was achieved using ‘‘rope lights’’ generally used as a garden decoration, secured to the outside of the carpet path. 2.3. Experimental protocol Instructions were given to the participants to walk at their own comfortable pace and to try to avoid hitting or touching any of the obstacles. Participants were free to choose their own avoidance strategy. Starting positions were randomized for the two lighting blocks and initial lighting levels, NORM or LOW, were counterbalanced between the participants. Progression through the obstacle course was monitored with two main methods, timing and the number of obstacle contacts. Timing was recorded as an overall completion time
Table 1 Participant characteristics and clinical test scores Subject
Age (years)
Age group
Gender
TUG (s)
ABC average score (%)
10 m (s)
Inside
Outside
Reach
1 2 4 5 14 15 17
84 81 75 80 78 84 84
Middle-old Middle-old Middle-old Middle-old Middle-old Middle-old Middle-old
M M M M M M F
9.5 13.5 9.7 17.2 15.4 12.5 10.4
94.2 90.7 95.7 94.2 62.8 81.8 95.7
88 73 78 80 64 80 90
87.5 71.3 100.0 92.5 76.2 80.0 76.2
11.2 13.4 12.5 11.9 13.4 13.1 10.4
3 6 7 8 11 13 16 18 19 20
89 93 94 86 85 88 90 85 89 90
Old-old Old-old Old-old Old-old Old-old Old-old Old-old Old-old Old-old Old-old
M F F M F F F M M F
12.7 9.8 13.7 9.2 13.2 16.2 17.4 16.6 7.7 12.1
94.2 96.4 97.1 96.4 88.6 57.1 62.1 78.5 82.8 50.7
82 90 92 90 80 64 51 73 90 48
72.5 75.0 87.5 62.5 80.0 45.0 52.5 72.5 61.2 52.5
12.0 10.8 14.2 9.7 11.8 19.6 17.5 17.5 8.7 10.1
Note: Activities-specific Balance Confidence (ABC) scores are divided into three different task categories—inside, outside and reach activities.
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Fig. 1. Schematic diagram of the obstacle course. Dotted lines indicate rope lighting used during the LOW lighting condition. Sections one and two contained three obstacles each: a duck (suspended from ceiling), step and circumvent. Section three contained two obstacles of each type. Obstacle contrast was distributed with section one high contrast (white obstacles), section two low contrast (black obstacles) and section three mixed contrast (both black and white obstacles). Start sections indicate three start positions randomized throughout the trials.
of the three-section course circuit, and the type and location of obstacles contacted was recorded. The obstacle course was navigated starting at each section (one, two or three) four times for total of 12 trials in the NORM and 12 trials in the LOW light conditions. As the obstacle course contained a total of 12 obstacles, the maximum number of contacts possible was 144 (12 total obstacles per trial 12 trials) for each lighting condition. A 10 min rest break was scheduled during the change in light condition to reduce the effects of fatigue and allow for visual accommodation. Additional rest breaks were given throughout the protocol, or when the participant requested. 2.4. Data analysis Participants were grouped for all analyses into two age categories [16]: middle-old (age 75–84 years; n = 7) and old-old (age 85 years and over; n = 10). 2.4.1. Obstacle course performance The total number of obstacle contacts made by each participant during the obstacle course was calculated for both lighting conditions (maximum number of contacts possible, 144 in either condition). Separate two-tailed (a = 0.05) Mann–Whitney non-parametric analyses were conducted on the number of contacts made (dependant variable) with respect to lighting condition, obstacle contrast, sex and age (independent variables). 2.4.2. Timing Non-parametric statistical analyses, two-tailed (a = 0.05) Mann–Whitney and Wilcoxon Signed Ranks tests, were conducted to analyze the overall total time required by participants to complete the obstacle course. 2.4.3. Type of obstacle hit A mixed repeated measures model analysis of variance (ANOVA) with post hoc Bonferroni corrected paired t-tests (95%) was performed in order to determine if there were differences in the types of obstacles hit (dependant variable) between the two age groups and the two lighting conditions (independent variables).
2.4.4. Balance confidence and functional capabilities Clinical test scores on the ABC questionnaire were set as dependent variables in non-parametric methods of analysis. Each participant’s overall average score for confidence on the ABC activities were analyzed, separated as a function of activity type, outside, inside and reaching activities. The rationale for the separation of these activities from one another was that the average scores for each category would provide insight into the type of activities that would possibly be perceived as more challenging for one age group versus another. Functional capabilities were then assessed using a univariate ANOVA model of the Timed Up and Go scores related to the number of obstacle contacts and total time to complete the course. Finally, the 10 m walk times were analyzed using a non-parametric Mann–Whitney (a = 0.05) to determine whether any non-obstructed self-selected speed differences existed between the two age groups.
3. Results Self-reports of activities enjoyed on a daily basis revealed walking (100% middle-old, 70% old-old) to be the most frequent followed by participation in a half an hour fitness classes three times a week (71% middle-old, 40% old-old). Of the middle-old (n = 7) group, only 57% reported using a walking aide (cane) and 14% reported having experienced a fall within the last 2 years. A fall was defined as an unexpected movement by which the participant contacted a lower surface during a routine activity, and did not occur due to fainting or illness. Of the old-old group (n = 10), 40% reported using walking aides (cane) and 30% reported a fall within the last 2 years. Participants with walking aides reported that their use was restricted to outdoor walking, and therefore chose not to use their aide during the testing protocol. 3.1. Obstacle course performance Results of the individual non-parametric analyses indicated significant effects ( p < 0.05) between the total numbers of contacts made during obstacle course negotia-
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Fig. 2. Total number of obstacle contacts made (in brackets) by the middleold and old-old age groups in each lighting condition. The old-old group contacted significantly more obstacles (*p < 0.05) compared to the middleold group in both lighting conditions.
tion for three of the independent variables: lighting condition, age and sex. However, obstacle contrast was found to not significantly affect the number of obstacle contacts ( p = 0.591). Analyses of obstacle contacts, in each lighting condition by age, revealed an interesting finding, the old-old age group contacted significantly more obstacles than the middle-old group in both lighting conditions ( p < 0.05; Fig. 2). 3.2. Timing In general, all participants decreased the speed with which they completed the course in the LOW lighting condition (two-tailed significance, p < 0.001; Fig. 3). Mean time for course completion collapsed across age groups were 22.3 7.2 s in NORM and 25.6 7.6 s in LOW. 3.3. Type of obstacle hit A significant interaction was observed between the type of obstacle hit and the two age groups (F (2,10) = 4.148, p = 0.049). Further analysis revealed that the interaction involved the step and hanging obstacles (F (1,11) = 8.828, p = 0.013). Paired t-tests between the age groups for both
Fig. 3. Time (s) for completion of one circuit (three sections) of the obstacle course in the NORM (white) and LOW (shaded) lighting condition for both age categories. Both age groups significantly increased time for course completion in the LOW lighting condition.
Fig. 4. Number of obstacle contacts for the two lighting conditions NORM (white) and LOW (shaded). Significant differences ( p < 0.05) are indicated by (*) and trends are indicated by (^).
lighting conditions indicated that the old-old group tended to contact the hanging obstacle more often than the middle-old group ( p = 0.054), whilst the middle-old tended to contact the step more often ( p = 0.142). Within the old-old group, different responses to the types of obstacles contacted and two lighting conditions were observed. The hanging obstacle was contacted significantly more than the step ( p = 0.002) and column ( p = 0.042) obstacles. As well, more contacts of the column and hanging obstacles were made in the LOW light condition compared to the NORM light condition ( p = 0.026 and 0.005, respectively). Within the middle-old group, a more consistent number of contacts across the types of obstacles and lighting conditions was observed, with the exception of the column obstacle which they contacted significantly more often in the LOW lighting condition ( p = 0.045; Fig. 4). 3.4. Balance confidence and functional capabilities The categorical analysis for the inside, outside and reaching tasks contained in the ABC evaluation tool revealed no significant difference in confidence ratings for outside and inside activities between the age groups (twotailed significance, p = 0.759 and 0.706, respectively). A significantly different confidence rating was obtained for the reaching tasks (two-tailed significance, p = 0.033). Additionally, the TUG scores (mean scores 12.5 3.0 s for the middle-old and 12.9 3.3 s for the old-old group) and 10 m walk times (1.2 0.06 and 1.4 0.14 m/s for the middleold and old-old participants, respectively) revealed no significant differences in functional capabilities between the two age groups (F (1,13) = 0.080, p = 0.782 and two-tailed significance, p = 0.922). Thus, on a straight unobstructed walking path the old-old group was not significantly slower than the middle-old group.
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4. Discussion Participants were recruited from the same retirement facility to ensure homogeneity in their exercise and social environments as well as the mobility challenges encountered in their daily living environment (crowded dining hall, etc.). Comparison of mobility to a younger population was felt to be counterintuitive to the objectives of this study as responses to experimental protocol for a younger population might be different due to the nature of the aging process and/ or a dissimilar lifestyle or ADLs. 4.1. Functional capabilities and balance confidence Functional capabilities and balance confidence assessed using the TUG, 10 m walk and ABC tests were not significantly different between age groups, indicating that all participants were similar in mobility function and balance confidence. Differences in obstacle avoidance performance were therefore not directly related to balance confidence or functional abilities evaluated in this study. The only exception was in the reach category, however this finding was driven by the response to one question (standing on a chair and reaching) and therefore not relevant to our current research questions. 4.2. Obstacle avoidance strategies Avoidance strategies adopted by the middle-old and oldold groups were similar in several ways. In response to the LOW lighting condition, both the age groups adopted a decreased speed strategy. This particular strategy has been reported in related literature as a typical response to decreased ambient lighting during obstacle course navigation [11,17]. Decreased walking speed has been attributed to a more cautious gait pattern in order to reduce the risk of instability possibly resulting in a fall [6] and in response to obstacles along the travel path [18,19]. Although the old-old group adopted similar cautious strategies as the middle-old group, their ability to accommodate their locomotor patterns to the environment was less successful as they contacted significantly more obstacles compared to the middle-old group. The increased number of contacts in this age group may indicate that these individuals have mobility deficiencies and are at a higher risk for falling when navigating a cluttered environment, as most incidents of falls occur during ambulation [7–9]. Unexpectedly, the contrast of the obstacles did not have a significant effect on whether the obstacles were contacted. It was hypothesized that more contacts would occur with low contrast obstacles, as these obstacles are more difficult to see especially in the LOW lighting condition. Previous work has identified obstacle contrast as an important factor in obstacle navigation in support of the above hypothesis [11,17]; however, this hypothesis was not supported by the current work. More drastic changes in contrast, i.e. placing a black obstacle on a white carpet, may have yielded a contrast
effect; however, the current study used industrial grey carpet, commonly used in supportive care facilities. A significant gender difference was found for number of obstacles contacted. However, this may have been driven by an unequal division of gender between the two age groups (old-old: six females and four males; middle-old: six males and one female). Future investigations into possible gender differences are necessary to further explore this finding. 4.3. Type of obstacle contacted A possible explanation for the differences observed between the types of obstacles for the two age groups may be related to the spatial frame of reference used during the task. During locomotor tasks, allocentric and egocentric spatial frames of reference are used to navigate our environment [20,21]. Wu [5] reported age-related changes in the upper body orientation during perturbed standing and suspected that an egocentric head centred reference frame is not well stabilized in older adults compared to young adults. A rigid strategy where the head is stabilized on the trunk may be adopted in order to reduce the number of degrees of freedom that have to be controlled during complex intersegmental movements [22]. Adopting this posture could in fact lead to instability, as the head–trunk segmental unit may incur greater excursions of the center of mass (COM) during locomotion, reducing one’s tolerance to postural disturbances [5]. This strategy may further explain the increased incidence of unsuccessful ducking and circumvention manoeuvres observed in the old-old participants. Although Wu reported no significant differences in rigidity within the older age groups themselves, participants in this previous work are appreciably younger (oldest group, 73.5 2.0 years) than the present study (85.6 5.2 years). Changes in segmental control during locomotion may occur over the age of 85 years that are, as of yet, unknown. Further investigation into segmental co-ordination and locomotor control are necessary to identify age-related changes. This work will increase our understanding how these changes influence or impact the ability of older adults to navigate complex environments. Another explanation for the old-old group contacting the hanging versus stepping obstacle could be related to the perceived threat of the different obstacles. If the stepping task was indeed more threatening to this old-old group, their full attention might be focused on clearing the stepping obstacle task with the result of making more contacts with the hanging and column obstacles. The increased incidence of old-old adults contacting the hanging obstacle is of critical importance to these individuals as hanging obstacles could pose a safety threat to older an adult’s balance. Further complications such as loss of consciousness or the acquisition of a serious head injury may be added to the loss of postural stability. Avoidance of hanging obstacles is a task that is often encountered (i.e. ducking under an open cabinet). The increased number of obstacle contacts observed in the LOW light condition for both the age groups in
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comparison to the number of contacts made in the NORM light condition (Fig. 2) suggest an increased risk for loss of balance and perhaps falls in reduced lighting conditions. Such evidence is compelling as it suggests the importance of adequate ambient lighting conditions in retirement facilities for the prevention of falls in older adults. Previous studies have reported similar increases in falls risk during low light conditions [11]. Further research is currently under way in our laboratory to investigate the effects of ambient room lighting on locomotor behaviour and changes in the segmental coordination of older adults in cluttered environments.
5. Conclusion There is a limited amount of research investigating obstacle avoidance in older adults and none that looks specifically at a supportive care facility-dwelling population. Although our study is limited due to a small number of subjects, it outlines underlying relationships regarding obstacle navigation for this specific population. Perhaps a larger sample population would reveal significant results where trends were observed in the current work. Middle-old and old-old adults differed with respect to the number and type of obstacles contacted and both groups contacted more obstacles when lighting was reduced. We propose that these discrepancies may be related to different locomotor reference frames used by the two populations and/or a difference in the perceived postural threat of obstacles in their environment.
Acknowledgements Financial support was received from the University of Guelph (RJR and LAV). We acknowledge and would like to thank kinesiologists Jennifer Hartwick and Jennifer Perry, the management, support staff and residents of The Village of Riverside Glen, Guelph, Ont., as well as Oakwood Retirement Community Facilities.
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