RESEARCH AND PRACTICE

Utilitarian Walking, Neighborhood Environment, and Risk of Outdoor Falls Among Older Adults Wenjun Li, PhD, Elizabeth Procter-Gray, PhD, Lewis A. Lipsitz, MD, Suzanne G. Leveille, PhD, Holly Hackman, MD, MPH, Madeleine Biondolillo, MD, and Marian T. Hannan, DSc, MPH

Falls are the leading cause of unintentional fatal and nonfatal injuries in older adults aged 65 years and older.1,2 In the United States, one third of older adults fall each year, with approximately 10% of falls resulting in injuries that need medical attention.1,3---5 Regular walking has been associated with numerous health benefits among older adults, including lower risk of cardiovascular diseases, obesity, diabetes, disabilities, and mortality.6---10 Utilitarian walking can be operationally defined as walking to shop and do other necessary errands or tasks of daily life. Both recreational and utilitarian walking have been widely recommended to older adults to improve balance, muscle strength, and general health7,10,11 and thus reduce fall risk. Utilitarian walking is particularly important to older persons with physical limitations who can no longer drive routinely or to those who cannot afford to drive. Unfortunately, walking is also the most common activity leading to falls and fall injuries among older adults,12 with 36% to 63% of outdoor falls occurring while walking.12---17 Experiencing an outdoor fall may result in the development of a psychological barrier to physical activity in those prone to falling, thus leading to decreased independence and mobility and increased likelihood of becoming homebound.18,19 Recent municipal and state initiatives have aimed at improving the safety of walking areas.20 Although these efforts are laudable, investments appear to be aimed more toward recreational walking, improving areas such as trails, tracks, and parks rather than utilitarian walking environments, possibly more crucial for the socioeconomically disadvantaged. We investigated the associations between the walking habits of older adults, the socioeconomic status (SES) of their neighborhoods, and the occurrence of outdoor falls.

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Objectives. We examined the roles of utilitarian and recreational walking in relation to occurrence of outdoor falls in older adults. Methods. We analyzed data on walking habits, falls, and fall injuries among participants of MOBILIZE Boston, a prospective cohort study of 765 communitydwelling women and men, mainly aged 70 years or older, in Boston, Massachusetts. Neighborhood socioeconomic status (SES) indicators were assessed at census block group level. Falls were recorded during a total of 2066.5 person-years of follow-up (September 2005–December 2009), and the median length of follow-up was 2.9 years (range = 0.04–4.3). Results. Lower neighborhood SES indicators were associated with more utilitarian walking and higher rates of falls on sidewalks, streets, and curbs. Falls on sidewalks and streets were more likely to result in an injury than were falls in recreational areas. Utilitarian-only walkers tended to live in neighborhoods with the lowest neighborhood SES and had the highest rate of outdoor falls despite walking 14 and 25 fewer blocks per week than the recreational-only and dual walkers, respectively. Conclusions. Improving the safety of walking environments in areas where older adults shop and do other errands of necessity is an important component of fall prevention. (Am J Public Health. 2014;104:e30–e37. doi:10.2105/AJPH. 2014.302104)

METHODS The MOBILIZE Boston Study has been described in detail elsewhere.21,22 Briefly, it was a prospective cohort study to identify novel risk factors and mechanisms of falls among 765 community-dwelling men and women, mainly aged 70 years and older, who lived in the Boston, Massachusetts, area. Other eligibility criteria included ability to read and speak in English, ability to walk 20 feet without the assistance of another person, intention to stay in the Boston area for at least 2 years, and adequate cognition for participation (‡ 18 points on the Mini-Mental Status Exam).23 Enrollment took place from September 2005 to December 2007 via door-to-door recruitment in randomly sampled households with at least 1 member aged 70 years or older as recorded in annual town lists required in Massachusetts. From 5655 sampled households, 4303 people aged 70 years or older were identified. Of the 4303 individuals, 1581

were not eligible, and 1973 either refused to participate or were unable to be contacted. An additional 16 persons aged 64 to 69 years who were spouses or living with a participant and otherwise eligible joined the study, for a total of 765 participants.

Data Collection At baseline, comprehensive assessments were completed during a clinical examination and home interview visit and through selfadministered questionnaires. During the clinical examination, we assessed participant body height and weight, which were used to calculate body mass index (BMI; defined as weight in kilograms divided by the square of height in meters). Balance was measured with the Berg Balance Scale Test.24 A person with a score lower than 45 was considered to have a balance deficit and an increased risk of falling.25 An inability to stand from a chair without using arms was taken as an indicator of poor lower-extremity muscle

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strength. Lower-extremity function was assessed by the Short Physical Performance Battery.26 Gait speed was assessed by the shortest time taken to complete a usual-paced 4-meter walk measured in meters per second. Distance vision was measured by a vision test completed from 10 feet; poor vision was defined as 40/100 or worse. During the home interview visits, trained interviewers administered questionnaires to assess the participant’s general health, chronic diseases,27 functionality, health behaviors,28 fall history in the 12 months prior to baseline, medication adherence, and sociodemographic characteristics. As previously described,29 activities of daily living were scored on the ability of the participant to perform 5 activities (transferring, bathing, dressing, toileting, and eating). The number of comorbid conditions was determined by self-report in response to a query on whether a health care provider had told the patient that he or she had any of several medical conditions.30 Medication use was reported as the number of over-thecounter and prescription medications used in the past 2 weeks. Psychotropic medications were classified separately. Fear of falling was measured with the Falls Efficacy Scale.19 Cognitive function was assessed with the MiniMental Status Exam. General health was determined at the end of the home visits by asking participants to self-rate their health (excellent, good, fair, or poor).

Walking Habits Participants were asked specific questions about their walking habits and whether they did any walking outside their home; if so, they were instructed to estimate the number of blocks they walked per week (12 blocks = 1 mile) for any purpose. They were also asked if they had difficulty walking a quarter mile. The frequency of outdoor walking was assessed with the question, “Over the past 7 days, how often did you take a walk outside your home or yard for any reason? (never, seldom [1---2 days], sometimes [3---4 days], or often [5---7 days]).” Utilitarian walking was defined as answering “yes” to the query, “Do you walk to the store, post office, bank, or other businesses in your neighborhood?” Recreational walking was defined as answering “yes” to the query, “Besides walking to stores or

businesses, do you walk for exercise in your neighborhood?” We obtained walking habit information for 750 of the 765 participants to classify each as (1) nonwalker (neither utilitarian nor recreational), (2) recreational-only walker, (3) utilitarian-only walker, or (4) dual walker (both recreational and utilitarian). The frequencies of utilitarian and recreational walking were categorized as less than once per week, 1 to 2 times per week, and 3 or more times per week.

Characteristics of Participants’ Neighborhoods The census block group of each participant was identified by geocoding his or her home address with ArcGIS Desktop 10 (ESRI 2011, Redlands, CA) and linking the geographic coordinates to US Census block group maps. Of the 765 participants, 760 (99.3%) participant home addresses were successfully geocoded, representing 300 different census block groups. Block group---level SES indicators were extracted from the 5-year rolling averages of American Community Surveys 2005 to 2009, the same period as the participants’ follow-up.

Ascertainment of Falls and Fall Circumstances and Consequences Falls were recorded during a total of 2066.5 person-years of follow-up (September 2005--December 2009), and the median length of follow-up was 2.9 years (range = 0.04---4.3). Participants were instructed during the home visit to keep a daily falls calendar, which was mailed to the study staff on a monthly basis. A fall was defined to the participant as being an event that resulted in unintentionally coming to rest on the ground or a lower surface. At the end of each month, participants mailed their monthly falls calendar postcard to the study office. Study staff telephoned those who did not return calendars within 10 days of the end of a month or who returned an incomplete calendar. Information on whether a fall had occurred was obtained for more than 99% of follow-up months. For participants who reported a fall, study staff would conduct a structured telephone interview to ascertain the circumstances and consequences of the fall. Participants were asked to explain (1) what happened when they fell on (date), (2) what

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they were doing when they fell, (3) where they were when they fell, and (4) the condition of the fall surface (e.g., dry vs wet, hard vs soft). Fall locations, activities, and consequences were categorized by staff as detailed in Duckham et al.12 Falls were reported as causing injury if a participant self-reported being hurt in any way as a result of falling. A serious injury was defined as any of the following: bone fracture; sprain; pulled or torn muscles, tendons, or ligaments; joint dislocation; and concussion. This study used the rates of all falls, all indoor falls, all outdoor falls, and falls specifically on sidewalks, streets, and curbs.

Statistical Analysis We calculated descriptive statistics of selected participant characteristics for the 4 walker groups. Between-group differences in these characteristics were tested with the v2 test for categorical measurements and 1-way analyses of variance for continuous measurements. We estimated annualized rates of falls and associated 95% confidence intervals (CIs) on the basis of negative binomial distributions, with participant total follow-up period used as calendar time exposure. Fall rates were expressed as number of falls per 100 personyears. We used negative binomial regression models, which accounted for overdispersion of number of fall occurrences per person, to estimate rate ratios and associated 95% CIs for falls with respect to various walking and block-group characteristics. As indicated, some of the regression models were adjusted for composite risk scores to avoid confounding by personal characteristics that might differ between the groups being compared, to preserve degrees of freedom, and to simplify the analysis. First, we predicted composite indoor and outdoor fall risk scores for each individual by negative binomial regression given the individual’s scores in all of the following characteristics12,25: age, sex, race/ ethnicity, education level, self-rated health, bodily pain, alcohol consumption, BMI, lowerextremity function, falls efficacy, activities of daily living, foot pain, knee osteoarthritis, number of falls in the year before baseline, balance, number of comorbidities, gait speed, peripheral neuropathy, having 3 or more flights of stairs in the home, cognitive function, number of medications, psychotropic

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medications, depression, poor vision, illness causing reduced activity in past year, and strength to rise unassisted from a chair. Participants living in the same block group were treated as a cluster to account for block group--level clustering effects. We estimated crude and composite-score-adjusted associations between block-group characteristics and walking habits with logistic regression models that treated individuals living in the same block group as a cluster. The composite scores were made up of all the factors listed earlier that were found to be associated with either walking 3 or more blocks per week, utilitarian walking, or recreational walking at the P < .1 level. Seemingly unrelated estimation models were used to test the equivalence of the associations of a given block-group SES indicator with utilitarian walking and recreational walking. We performed sensitivity tests in the analyses to determine whether the associations observed would differ (1) when 219 people who claimed to have difficulty walking a quarter mile were excluded or (2) when models were adjusted for the season of the home interview. Neither of these variations significantly affected the results with regard to walking habits or fall outcomes. All statistical analyses were carried out with Stata MP 12 (StataCorp LP, College Station, TX).

RESULTS A total of 1766 falls were reported during the course of this study, with an overall fall rate of 83 (95% CI = 76, 92) per 100 person-years. Outdoor falls accounted for 46% of the falls and had a rate of 38 (95% CI = 34, 43) per 100 person-years. Rate of falling was 15 (95% CI = 13, 18) per 100 person-years on sidewalks, streets, or curbs; 11 (95% CI = 9, 13) per 100 person-years in private garden, yard, or walk; and 6 (95% CI = 4, 9) per 100 person-years in public parks or recreational areas. The most common activity related to outdoor falls was walking (45%). As shown in Table 1, the 4 walker groups differed in many personal, behavioral, and health characteristics. The largest differences were observed when comparing nonwalkers with the other 3 walker groups. Nonwalkers were likely to be the least educated and least

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healthy, whereas recreational-only walkers had the highest education level, the highest percentage of White race, the highest falls efficacy, the best self-rated health, and the lowest depression score. Dual walkers were the youngest, had the lowest mean BMI, were highly educated, had the highest mean number of blocks walked per week, and had the highest scores for the Short Physical Performance Battery, Physical Activity Scale in the Elderly, Berg Balance Scale Test, and gait speed. Utilitarian-only walkers had the fewest comorbidities, were the least likely to have reduced activity in the last year because of an illness, and were the least frequent users of alcohol or medications. The block group---level characteristics of the 4 walker groups differed significantly also. The utilitarian-only walkers had the lowest mean block group---level per-capita income, the highest percentages of being below poverty level and on public assistance, the lowest rate of home ownership and proportion of persons living in the same house as the previous year, the highest percentage of walking to work, and the highest percentage of Hispanic ethnicity. Annualized rates of outdoor, indoor, and total falls are summarized by walker group in Table 2. Utilitarian-only walkers had the highest rates of outdoor and total falls with and without covariate adjustment. By comparison, nonwalkers had the highest rates of indoor falls with and without covariate adjustment. Dual walkers had the highest proportion of outdoor falls (56.1%). As shown in Table 3, higher outdoor fall rates were associated with several indicators related to increased exposure to outdoor walking, including greater number of blocks walked per week, more frequent outdoor walking, any utilitarian walking, and belonging to a walker group. The utilitarian walking and falls association was retained after covariate adjustment. Walking for recreation alone was associated with higher outdoor fall risk (P < .05) in the unadjusted model only. These walking measures were predictive of higher rates of outdoor falls but not of indoor falls. Likelihood of fall injury associated with outdoor walking differed by place. Falls on sidewalks and streets were more likely to result in an injury than were falls in recreational areas (55% vs 24%; odds ratio [95% CI] = 3.8 [2.4,

6.1]; P < .001) and were more likely to be associated with a serious injury that needed medical attention (e.g., fracture, sprain, dislocation, and concussion; 11.8% vs 3.4%; odds ratio [95% CI] = 3.9 [1.3, 11.0]; P = .01). Falls on sidewalks, streets, and curbs were more likely to be related to slipping or tripping compared with falls in recreational areas (71% vs 60%; P = .04). Several block group---level indicators of lower SES were associated with greater likelihood of utilitarian walking, including per-capita income less than $12 500 (inflation-adjusted 2009 dollars), greater percentage with income below poverty level, lower percentage of owner-occupied housing units, and greater turnover in housing occupancy (Table 4). However, none of these characteristics were associated with recreational walking. Both percentage of racial/ethnic minorities and percentage of vacant housing units had a U-shaped association with utilitarian walking. Neighborhoods with the highest vacancy and minority concentration had less utilitarian walking. All of the block-group variables shown in Table 4, except for percentages of unemployment, receiving public assistance, and being racial/ ethnic minorities, had significantly different associations with utilitarian versus recreational walking (seemingly unrelated estimation test for equivalence: P < .05), with utilitarian walking invariably having a stronger association with lower-SES indicators. The rate of all outdoor falls was not associated with any block-group characteristic except percentage of Hispanic residents greater than 15 (adjusted rate ratio [95% CI] = 1.4 [1.1, 1.9]). However, several block group---level lower-SES indicators were associated with higher rates of outdoor falls on sidewalks, streets, and curbs, which accounted for the greatest proportion of outdoor falls (39.5%). Falls on sidewalks, streets, and curbs occurred at significantly higher rates in block groups with a greater percentage of the population below poverty level or on public assistance, a lower percentage of owner-occupied housing units, greater housing turnover, a greater percentage walking to work, and a greater percentage of minority or Hispanic individuals. The association of utilitarian walking with outdoor falls was highly significant in both lower-SES and higher-SES areas but much

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TABLE 1—Participant Characteristics by Walking Habits: MOBILIZE Boston Study; Boston, MA; September 2005–December 2009 Sociodemographic Female gender

Nonwalker (n = 228), Mean (SD) or %

Recreational Walker (n = 180), Mean (SD) or %

Utilitarian Walker (n = 91), Mean (SD) or %

Dual Walker (n = 251), Mean (SD) or %

Pa

67.5

63.3

63.7

61.0

.52

79.1 (5.9)

78.2 (5.2)

78.4 (5.4)

77.0 (5.1)

< .001

White race

74.1

86.6

76.9

75.7

.02

Highest education level completed £ high school graduate

41.7

24.4

35.2

34.8

Some college or bachelor of arts

34.2

41.7

36.3

28.4

Advanced degree

24.1

33.9

28.6

36.8

43.0

21.7

46.2

39.8

28.6 (5.5)

27.8 (5.5)

27.3 (4.7)

Age at baseline, y

Annual household income < $25 000

.002

< .001

Lifestyle Body mass index, kg/m2

26.6 (4.8)

< .001

89 (72.8)

110 (68.7)

99 (57.3)

126 (71.3)

< .001

18.6 (34.0)

51.6 (79.6)

37.9 (53.2)

62.8 (81.4)

< .001 .003

Every day

12.3

11.7

12.1

15.9

1–6/wk

17.5

35.0

20.9

26.3

1–3/mo

24.6

20.0

16.5

22.3

Not at all

45.6

33.3

50.5

35.5

47.3 (8.9)

50.6 (5.2)

49.9 (6.1)

51.4 (4.8)

< .001

17.1 33.8

3.3 18.9

3.3 20.9

3.6 14.7

< .001 < .001

Physical Activity Scale in the Elderly Blocks walked/wk Alcoholic beverage frequency

Physical disability Berg Balance Scale Inability to stand from a chair without using arms Difficulty with activities of daily living Short Physical Performance Battery score Gait speed (m/s) Reduced activity because of illness in past year

8.4 (3.0)

9.6 (2.2)

9.3 (2.4)

10.0 (2.0)

< .001

0.86 (0.25)

0.97 (0.27)

0.94 (0.22)

1.02 (0.25)

< .001

32.5

32.8

18.7

24.7

.02

Illness-related Fair-to-poor self-rated health

21.1

10.0

11.0

13.2

< .01

3.2 (1.6)

2.9 (1.5)

2.5 (1.4)

2.7 (1.5)

< .001

Moderate-to-severe bodily pain Foot pain on most days

51.3 23.7

36.1 28.9

33.0 26.4

32.9 20.3

< .001 .21

Knee osteoarthritis

26.3

22.8

28.6

23.9

.69

Peripheral neuropathy

16.9

9.4

11.0

10.0

.06

8.8

5.6

12.2

8.8

.31

20.8

24.0

15.6

18.6

.35

0–4

28.5

29.4

40.7

42.2

5–8 ‡9

47.4 24.1

50.0 20.6

42.9 16.5

41.0 16.7

No. of comorbid conditions (excluding depression)

Vision worse than 40/100 Use of psychotropic medication No. of medications

.02

Center for Epidemiologic Studies Depression Scale

12.5 (12.7)

9.9 (8.6)

12.5 (11.0)

10.0 (11.5)

.02

Mini-Mental Status Exam for elderly (< 18 excluded)

26.9 (2.7)

27.4 (2.4)

26.9 (2.7)

27.0 (2.8)

.2

Fall history and home setting Falls efficacy scale (100 max)

94.0 (11.7)

97.1 (6.3)

95.2 (10.0)

96.3 (8.1)

< .01

No. of falls in year before baseline

0.79 (1.3)

0.66 (1.5)

0.76 (1.3)

0.90 (3.7)

.78

9.7

8.9

11.0

15.5

.11

‡ 3 flights of stairs in home

Continued

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TABLE 1—Continued Neighborhood characteristics (census block group level)b Per-capita income, $1000s

42 (22)

49 (22)

41 (22)

43 (22)

% below poverty level

11 (12.7)

7.9 (9.1)

16.8 (15.2)

14.1 (13.9)

< .01 < .001

% of housing units owner occupied

62.4 (26.3)

69.9 (23.2)

46.9 (26.8)

52.5 (26.0)

< .001

% in same house as previous year

85.9 (11.2)

85.7 (10.5)

80.4 (13.9)

81.8 (11.9)

< .001

% of housing units vacant % of adults who work

6.5 (8.0) 81.2 (9.2)

5.7 (7.9) 82.9 (7.7)

7.4 (6.2) 80.5 (10.1)

6.3 (6.3) 81.3 (11.8)

.37 .21

% on public assistance

3.1 (4.9)

1.8 (3.6)

3.4 (5.8)

2.8 (5.4)

.03

% of workers who commute by walking

4.2 (7.6)

3.9 (6.7)

8.4 (10.8)

7.4 (9.8)

< .001

36.6 (32.9)

24.9 (26.3)

34.1 (30.0)

34.0 (29.4)

< .001

8.7 (11.2)

6.1 (9.7)

11.1 (12.4)

9.4 (12.0)

< .01

% minority (non-White) % Hispanic

P value for testing differences among 4 walker groups. The Kruskal-Wallis rank test was used for continuous variables, and the v2 test was used for categorical variables. Census block group–level socioeconomic status indicators were extracted from the 5-year rolling averages of American Community Surveys 2005 to 2009, the same period as the participants’ follow-up. a

b

stronger in low-SES areas (rate ratio [95% CI] = 3.7 [1.8, 7.5] vs 1.7 [1.2, 2.3]). These results suggest that utilitarian walking may be especially hazardous in the low-SES areas.

DISCUSSION Previous literature reported multiple health benefits of regular walking, including both recreational and utilitarian walking. Utilitarian walking, as a form of moderate physical activity, has been widely recommended to adults to prevent obesity and other chronic diseases. However, the elevated risk of outdoor falls associated with utilitarian walking among the older adults has not been well addressed in literature or adequately considered when promoting walking as a form of physical activity. The results from the MOBILIZE Boston Study suggest the necessity of separating recreational and utilitarian walking when analyzing risk of outdoor falls. Compared with falls

in recreational areas, falls on sidewalks and streets were twice as likely to result in an injury and nearly 4 times as likely to result in a serious injury that needed medical attention. Therefore, the injurious potential of utilitarian walking should be taken into account when promoting walking activities among older adults in socioeconomically disadvantaged neighborhoods. The results from this study showed notable socioeconomic disparities in walking behaviors and associated risk of outdoor falls, even after adjusting for a long list of known risk factors. Older adults living in socioeconomically disadvantaged neighborhoods were more likely to walk for utilitarian purposes only and less likely to walk regularly for recreation. It is interesting to observe that utilitarian walkers did not have a poorer health profile or other inherent factors that would put them at greater risk for falls than other walker groups. In addition, compared with recreational walkers, utilitarian-only

walkers walked fewer blocks per week on average but reported the highest rates of outdoor falls among the 4 walker groups, a fact explained by neither intrinsic risk factors nor exposure time (blocks walked) or the combination of the 2 aspects. By contrast, indoor fall rates were not elevated among utilitarian-only walkers. These observations suggest that walking for utilitarian purposes may be associated with a higher risk of outdoor falling, perhaps as a result of hazards in the walking environment or other behavioral factors not measured in the MOBILIZE Boston Study. It is reasonable to query whether the disparities in outdoor fall rates were related to participants’ neighborhood walking environment. The study observed that significantly higher rates of falls on sidewalks, streets, and curbs, the most common sites of outdoor falls in our study, were associated with many block group---level lower-SES indicators. For instance, older adults living in block groups with median

TABLE 2—Crude and Covariate-Adjusted Annual Rates of Outdoor, Indoor, and Total Falls, by Walker Group, per 100 Person-Years: MOBILIZE Boston Study; Boston, MA; September 2005–December 2009 Outdoor Falls Walker Group

Crude Rate (95% CI)

Adjusted Rate (95% CI)

Indoor Falls Crude Rate (95% CI)

Total Falls

Adjusted Rate (95% CI)

Crude Rate (95% CI)

Adjusted Rate (95% CI)

% Outdoors

Nonwalker

26 (20, 33)

19 (15, 25)

52 (44, 63)

38 (31, 46)

79 (67, 93)

63 (53, 74)

32.9

Recreational walker

36 (28, 46)

23 (17, 30)

45 (34, 58)

30 (24, 39)

81 (66, 99)

61 (50, 74)

44.4

Utilitarian walker

50 (36, 68)

34 (25, 46)

43 (28, 66)

26 (18, 39)

95 (70, 129)

70 (53, 91)

52.6

Dual walker

46 (37, 56)

26 (21, 32)

35 (28, 43)

25 (20, 31)

82 (69, 99)

56 (47, 66)

56.1

Note. CI = confidence interval.

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TABLE 3—Incidence Rate Ratios for Outdoor and Indoor Falls, by Participant Walking Habits: MOBILIZE Boston Study; Boston, MA; September 2005–December 2009 Outdoor Falls Walking Habit

No.

Indoor Falls a

Adjusted IRR (95% CI)

Crude IRR (95% CI)

No.

Crude IRR (95% CI)

Adjusteda IRR (95% CI)

Walk outside ‡ 3/wk No (Ref) Yes

502 1.00 1.00 502 1.00 1.00 256 1.53 (1.19, 1.97) 1.17 (0.93, 1.46) 256 0.76 (0.59, 0.98) 0.87 (0.69, 1.09)

Any utilitarian walking No (Ref)

408 1.00

1.00

408 1.00

1.00

Yes

342 1.55 (1.22, 1.98) 1.32 (1.07, 1.64) 342 0.75 (0.59, 0.96) 0.81 (0.65, 1.01)

Any recreational walking No (Ref)

319 1.00

Yes

433 1.29 (1.01, 1.66) 1.07 (0.86, 1.34) 433 0.77 (0.61, 0.98) 0.84 (0.67, 1.04)

No. blocks walked/wk < 2 (Ref)

112 1.00

1.00

1.00

319 1.00

112 1.00

1.00

1.00

2–9

148 1.45 (0.91, 2.32) 0.99 (0.63, 1.56) 148 0.83 (0.56, 1.23) 0.92 (0.64, 1.32)

10–24

173 2.50 (1.60, 3.89) 1.36 (0.88, 2.09) 173 0.76 (0.52, 1.12) 0.79 (0.55, 1.12)

25–74

164 2.19 (1.40, 3.43) 1.17 (0.76, 1.81) 164 0.54 (0.36, 0.80) 0.72 (0.50, 1.04)

‡ 75

137 2.67 (1.68, 4.23) 1.28 (0.82, 1.99) 137 0.43 (0.28, 0.66) 0.63 (0.43, 0.94)

How often walk outside Never (Ref)

114 1.00

Seldom Sometimes

174 1.31 (0.84, 2.03) 1.30 (0.87, 1.93) 174 1.04 (0.70, 1.54) 0.98 (0.69, 1.40) 213 1.78 (1.17, 2.70) 1.41 (0.97, 2.05) 213 0.95 (0.65, 1.39) 1.07 (0.76, 1.51)

1.00

114 1.00

1.00

Often

256 2.21 (1.48, 3.32) 1.50 (1.04, 2.16) 256 0.75 (0.52, 1.10) 0.89 (0.63, 1.25)

How often utilitarian walk Never (Ref)

408 1.00

< 1 time/wk

128 1.51 (1.08, 2.11) 1.33 (0.99, 1.80) 128 0.74 (0.52, 1.03) 0.78 (0.57, 1.06)

1 or 2 times/wk

109 1.35 (0.95, 1.93) 1.20 (0.88, 1.64) 109 0.86 (0.61, 1.21) 0.91 (0.66, 1.24)

‡ 3 times/wk

105 1.83 (1.30, 2.59) 1.45 (1.08, 1.96) 105 0.65 (0.45, 0.93) 0.75 (0.54, 1.04)

How often recreation walk Never (Ref) 319 1.00

1.00

1.00

408 1.00

319 1.00

1.00

when considering disparities in the health of older adults. We are currently analyzing the neighborhood built environment data to examine to what extent the observed socioeconomic disparities in walking behaviors and outdoor fall rates could be explained by the variations in walking environment.

Study Strengths This analysis had several strengths. First, the MOBILIZE Boston Study was a prospective study with 765 older adults followed up extensively for falls for up to 4.3 years. Experienced research staff obtained fall outcomes with monthly falls calendars and structured telephone interviews, which is the gold standard in fall epidemiology research.31 The participants were strategically recruited to represent a broad range of socioeconomic and residential conditions. As a result, more than 300 block groups were represented, and the demographic profiles of the cohort were perfectly matched with the underlying older adult population in the study area.21 In addition, a long list of known risk factors for falls, covering most known risk factors, were measured carefully, which affords the opportunity for comprehensive covariate adjustment when estimating the associations among walking habits, block-group characteristics, and falls.

1.00

< 1 time/wk

116 1.34 (0.93, 1.92) 1.15 (0.83, 1.57) 116 0.88 (0.62, 1.26) 0.95 (0.70, 1.30)

Study Limitations

1 or 2 times/wk

144 1.23 (0.88, 1.72) 1.19 (0.89, 1.60) 144 0.79 (0.57, 1.10) 0.91 (0.68, 1.22)

‡ 3 times/wk

172 1.30 (0.95, 1.79) 0.92 (0.69, 1.22) 172 0.68 (0.50, 0.93) 0.69 (0.52, 0.93)

This study also had several limitations. It was limited to 1 urban area in the northeastern region of the United States (Boston) where the older adult population tends to be more highly educated and have higher percentages of English-speaking White individuals. Information collected on the occurrence and circumstances of falls was based on self-report and subject to inaccuracies, but fall follow-up interviews were conducted promptly each month when falls were reported, and the overall rate of falls (0.83/ year) is comparable with that found in other studies. Detailed information on walking habits and selection of walking routes was not collected. Future studies may consider collection of detailed information on walking preference as

Walker group Nonwalker (Ref)

228 1.00

Recreational walker

180 1.41 (1.00, 1.99) 1.17 (0.86, 1.60) 180 0.84 (0.61, 1.16) 0.90 (0.67, 1.20)

1.00

228 1.00

1.00

Utilitarian walker Dual walker

91 1.95 (1.29, 2.95) 1.66 (1.15, 2.39) 91 0.82 (0.55, 1.23) 0.87 (0.61, 1.25) 251 1.79 (1.31, 2.45) 1.35 (1.02, 1.79) 251 0.65 (0.48, 0.88) 0.74 (0.56, 0.97)

Note. CI = confidence interval; IRR = incidence rate ratio. a Adjusted for a composite score predicted from the following personal characteristics: age, sex, race, education level, selfrated health, bodily pain, alcohol consumption, body mass index, activities of daily life ability, short physical performance battery, balance, gait speed, strength to rise from a chair, knee osteoarthritis, foot pain, peripheral neuropathy, number of comorbidities, poor vision, illness causing reduced activity in past year, Mini-Mental State Exam score, depression, number of medications, use of psychotropic medication, number of falls in year before baseline, falls efficacy, and flights of stairs in the home.

per-capita income less than $12 500 had almost twice the rate of falling on sidewalks, streets, and curbs when other fall risk factors

were taken into account. Neighborhood SES and built environment risk factors for outdoor falls are therefore a significant issue

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TABLE 4—Block-Group Characteristics and Their Associations With Walking Habits and With Falls on Sidewalks, Streets, and Curbs: MOBILIZE Boston Study; Boston, MA; September 2005–December 2009 OR for Walking Habit (95% CI)c Block-Group-Level Characteristica Mean (SD)b

Units

Rate Ratios for Falls on Sidewalks, Streets, and Curbs (95% CI)d

Walking Outdoors ‡ 3 d/wk

Utilitarian Walking

Recreational Walking

Per-capita income, $1000s

38.4 (22.9) < 12.5 vs ‡ 12.5

1.83 (0.78, 4.32)

1.98* (1.04, 3.79)

0.76 (0.33, 1.71)

% with income < poverty level % owner-occupied

14.6 (15.0) 53.7 (28.3)

> 20 vs £ 20 < 25 vs ‡ 25

1.63* (1.07, 2.50) 1.61 (0.93, 2.80)

1.65 (1.08, 2.51)* 2.08** (1.31, 3.31)

0.88 (0.61, 1.26) 1.06 (0.67, 1.70)

82.4 (13.3)

< 75 vs ‡ 75

1.26 (0.80, 2.00)

2.18** (1.31, 3.64)

0.86 (0.58, 1.27)

Crude 1.44 (0.73, 2.84)

Adjustede 1.83 (0.92, 3.66)

1.46 (0.98, 2.16) 1.75** (1.27, 2.40) 1.90** (1.26, 2.87) 1.98** (1.42, 2.76)

housing units % in same house as

1.52* (1.05, 2.20)

1.55* (1.13, 2.12)

previous year % housing units vacant (Ref)

7.3 (7.7)

0%

1.00

> 0–20 % adults who work % on public assistance % workers commute

1.00

1.00

1.00

1.29 (0.90, 1.84)

2.24** (1.53, 3.30)

1.00

1.11 (0.81, 1.52)

1.07 (0.75, 1.53)

1.08 (0.79, 1.47)

> 20

0.64 (0.32, 1.27)

0.84 (0.43, 1.64)

0.93 (0.49, 1.76)

0.87 (0.50, 1.51)

1.26 (0.79, 1.99)

80.8 (11.2) 3.4 (6.0)

< 70 vs ‡ 70 > 5 vs £ 5

1.85* (1.11, 3.08) 1.07 (0.71, 1.64)

1.53 (0.95, 2.48) 1.02 (0.65, 1.60)

0.96 (0.61, 1.52) 0.83 (0.58, 1.19)

1.15 (0.70, 1.89) 1.32 (0.82, 2.12)

1.26 (0.81, 1.96) 1.63* (1.12, 2.39)

6.3 (10.2)

> 10 vs £ 10

1.22 (0.77, 1.92)

3.09** (1.87, 5.09)

1.17 (0.79, 1.74)

1.53* (1.01, 2.30)

1.49* (1.03, 2.14)

40.7 (33.9)

£5

by walking % racial/ethnic minority

1.00

1.00

1.00

1.00

1.00

(non-White; Ref)

% Hispanic

11.0 (13.4)

> 5–95

1.19 (0.71, 1.99)

1.87 (1.06, 3.29)*

1.27 (0.72, 2.23)

> 95

1.37 (0.63, 2.97)

1.00 (0.42, 2.41)

0.91 (0.40, 2.06)

1.93* (1.15, 3.21) 2.60** (1.56, 4.32) 0.87 (0.37, 2.02)

1.83 (0.72, 4.65)

> 15 vs £ 15

1.22 (0.81, 1.84)

1.41 (0.93, 2.15)

0.84 (0.57, 1.23)

1.18 (0.80, 1.74)

1.53* (1.06, 2.21)

Note. CI = confidence interval; OR = odds ratio. Block group–level socioeconomic status indicators were extracted from the 5-year rolling averages of American Community Surveys 2005 to 2009, the same period as the participants’ follow-up. a Sociodemographic data from American Community Surveys (2005, 2009). b Based on 300 different block groups containing the sample population. c Estimates obtained with logistic regression models clustered by block group for 3 outcomes: frequency of walking outdoors (at least 3 days vs 2 days or less per week), utilitarian walking in neighborhood (yes vs no), and recreational walking in neighborhood (yes vs no). Each analysis was adjusted for a composite score predicted from the following personal characteristics: age, sex, self-rated health, bodily pain, alcohol consumption, education level, body mass index, short physical performance battery, falls efficacy, activities of daily life ability, race, foot pain, balance, number of comorbidities, gait speed, peripheral neuropathy, flights of stairs in the home, Mini-Mental State Exam score, number of medications, illness causing reduced activity in past year, and strength to rise from a chair. d Estimates obtained with negative binomial regression models clustered by block group. e Adjusted for a composite outdoor fall risk score predicted from the personal characteristics listed in footnote c plus osteoarthritis of the knee, number of falls in year before baseline, depression, poor vision, and psychotropic medication. *P < .05; **P < .005.

well as objectively measured walking data such as time and location of walking and selection of walking paths with accelerometer and Global Positioning System devices. Such data will help us better understand the complex relations between recreational and utilitarian walking and outdoor falls.

Conclusions These results have important implications for community-based fall prevention. When considering municipal initiatives to improve the safety of walking environments, not only recreational paths and public parks but also areas where older people shop and do other

e36 | Research and Practice | Peer Reviewed | Li et al.

errands of necessity should be taken into account. Fall prevention requires attention to both socioeconomic and built environment conditions, particularly in neighborhoods with high concentrations of older residents. Special consideration should be given to economically disadvantaged neighborhoods where fall rates tend to be relatively high and where local resources may be insufficient for the proper upkeep of safe sidewalks and streets. Ongoing studies of the built environment, including “walk audits” within individual neighborhoods, may elucidate the hazards and design features that are associated with high rates of falls to inform

policymakers of the most urgent improvements needed. j

About the Authors Wenjun Li and Elizabeth Procter-Gray are with the Health Statistics and Geography Lab, Division of Preventive and Behavioral Medicine, University of Massachusetts Medical School, Worcester. Lewis A. Lipsitz and Marian T. Hannan are with the Institute for Aging Research, Hebrew SeniorLife/Harvard Medical School, and Beth Israel Deaconess Medical Center, Boston, MA. Suzanne G. Leveille is with the College of Nursing and Health Sciences, University of Massachusetts, Boston. Holly Hackman and Madeleine Biondolillo are with the Massachusetts Department of Public Health, Boston. Correspondence should be sent to Wenjun Li, PhD, Associate Professor, Director, Health Statistics and Geography Lab, Preventive and Behavioral Medicine,

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Department of Medicine, University of Massachusetts Medical School, Shaw SH2-230, 55 Lake Ave N, Worcester, MA 01655 (e-mail: wenjun.li@umassmed. edu). Reprints can be ordered at http://www.ajph.org by clicking the “Reprints” link. This article was accepted May 12, 2014.

Contributors W. Li conceptualized the study. W. Li, S. G. Leveille, and M. T. Hannan obtained the funding. W. Li and E. Procter-Gray carried out the analysis, interpreted the statistical results, and drafted the article. L. A. Lipsitz, S. G. Leveille, and M. T. Hannan are the investigators of the MOBILIZE Boston Study, which collected the data. All authors contributed to the writing, reviewing, and approval of the final article.

Acknowledgments The study was funded by the National Institute on Aging (grant 5R01AG028738), which also funded research that generated data used in this study (grants 5R01AG026316, 5R37AG025037, and 5P01AG004390). Funding from Pfizer was used to code and classify medications. Note. Neither the National Institutes of Health nor Pfizer played any role in the design or conduct of the study; the collection, management, analysis, or interpretation of the data; or the preparation, review, or approval of the article.

Human Participant Protection The institutional review board of Hebrew SeniorLife approved this study; all participants signed a consent form.

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