Untitled

Land Use, Residential Density, and Walking
The Multi-Ethnic Study of Atherosclerosis
Daniel A. Rodríguez, PhD, Kelly R. Evenson, PhD, Ana V. Diez Roux, MD, PhD, Shannon J. Brines, MS
Background: The neighborhood environment may play a role in encouraging sedentary patterns, especially for middle-aged and older adults.
The aim of this study was to examine the associations between walking and neighborhood population density, retail availability, and land-use distribution using data from a cohort of Data from a multi-ethnic sample of 5529 adult residents of Baltimore MD, Chicago IL, Forsyth County NC, Los Angeles CA, New York NY, and St. Paul MN enrolled in the Multi-Ethnic Study of Atherosclerosis in 2000 –2002 were linked to secondary land-use and population data. Participant reports of access to destinations and stores and objective measures of the percentage of land area in parcels devoted to retail land uses, the population divided by land area in parcels, and the mixture of uses for areas within 200 m of each participant’s residence were examined. Multinomial logistic regression was used to investigate associations of self-reported and objective neighborhood characteristics with walking. All analyses were conducted in 2008 and 2009.
After adjustment for individual-level characteristics and neighborhood connectivity, it was found that higher density, greater land area devoted to retail uses, and self-reported proximity of destinations and ease of walking to places were each related to walking. In models including all land-use measures, population density was positively associated with walking to places and with walking for exercise for more than 90 minutes/week, both relative to no walking. Availability of retail was associated with walking to places relative to not walking, and having a more proportional mix of land uses was associated with walking for exercise for more than 90 minutes/week, while self-reported ease of access to places was related to higher levels of exercise walking, both relative to not walking.
Conclusions: Residential density and the presence of retail uses are related to various walking behaviors.
Efforts to increase walking may benefit from attention to the intensity and type of land development.
(Am J Prev Med 2009;37(5):397– 404) 2009 American Journal of Preventive Medicine pendent engagement in community life.2 Despite the importance of the built environment, there is a paucity y limiting opportunities for being physically ac- of studies examining its relationship to physical activity tive in everyday life, contemporary urban areasare believed to play a role in encouraging sed- entary patterns and obesity. Relative to young adults, Proximity to nonresidential land uses, specifically the role of the neighborhood environment as a barrier retail uses, has been linked to higher walking rates for or support of active lifestyles may be more pronounced utilitarian purposes in the general population.7–12 For for middle-aged and older adults.1 In addition to older adults, convenient access to nonresidential desti- physical activity benefits, for older adults a supportive nations has yielded inconsistent findings,6 although neighborhood environment may also encourage inde- recent studies using objective measures of the builtenvironment have shown more consistent associa-tions.3,13 Only one study3 has examined access to retail From the Department of City and Regional Planning (Rodriguez), land uses for older women, and the analysis was limited and Department of Epidemiology (Evenson), Gillings School of to department, discount, and hardware stores. Positive Global Public Health, University of North Carolina, Chapel Hill, associations were found between accessibility to retail North Carolina; Department of Epidemiology (Diex Roux), and School of Natural Resources and Environment (Brines), University of Beyond the presence of specific land uses, others Address correspondence and reprint requests to: Daniel A. Ro- have argued that the proportion of land devoted to dríguez, PhD, Department of City and Regional Planning, CB 3140 New East, 319, Chapel Hill NC 27599-3140. E-mail: [email protected].
different uses within a given distance from a home 2009 American Journal of Preventive Medicine • Published by Elsevier Inc.
location may also affect levels of physical activity.7,8,14 was developed using extensive qualitative research22 and has Areas with more proportional mixing of uses may be been shown to have acceptable test–retest reliability and supportive of walking because of the availability and validity among a sample of women.23 For each type of activity variety of destinations. Further, this diversity may be queried, participants were asked (1) whether they did the more important for populations with limited access to activity during a typical week in the past month and (2) howmany days per week and how many hours and minutes per automobiles, such as children and older adults.15 Thus, not only proximity to specific uses such as retail but also For this study, the focus was on the types of physical the relative intensity among uses within one’s neighbor- activities related to walking, which are most likely to be hood may help explain physical activity levels. For associated with two key land characteristics: the type of land example, a neighborhood with 95% of its parcel area use and the intensity of residential development. The two devoted to residential uses and 5% to retail has a walking behaviors examined were minutes per week in walk- different, less proportionate distribution of area among ing for transport (e.g., walking to get places such as to the bus, uses than a neighborhood with 30% of its parcel area car, work, or store), defined as walking to places; and minutes devoted to residential uses, 30% to retail, and 40% to per week walking for leisure (e.g., walking for exercise, institutional uses. Identifying associations of physical pleasure, social reasons, during work breaks, walking thedog), defined as walking for exercise. Given unavoidable activity with specific uses of land, such as retail, and the measurement error in reports of exact times of walking, the intensity at which land is developed provides planners data were categorized rather than investigated as a continu- with guidance to improve communities and future ous measure. Categories usually have better reliability than continuous measures and allow a parsimonious way to man- Relying on data from a large, multi-ethnic cohort of age data skewness. As a result, outcome variables were created adults aged 45 to 84 years, associations between self- by classifying each type of walking into three levels: no reported walking and neighborhood population density, walking, walking time that is less than the median of nonzero retail access, and land-use distribution, while controlling data, and walking time greater than or equal to the median for other environmental and individual characteristics, are examined. It is hypothesized that greater population Neighborhood Built Environment Characteristics
density and improved access to retail land uses are relatedto higher levels of walking for various purposes. Respond- Neighborhood information was collected in part by the MESA ing to calls for including objectively measured and per- Neighborhood Study, an ancillary study to MESA, whichincluded the geocoding of each participant’s home address.
ceptual environmental data simultaneously,16–18 the study All objective measures were derived using ArcGIS 9.2. Neigh- combines self-reported and objectively measured land-use borhoods were person specific, defined as the area covered by information. These analyses contribute to the understand- a circle of 200-m radius drawn around each person’s home ing of the role that the mixing of particular land uses can play in supporting physical activity in middle-aged and Land-use data were collected from municipal and regional older adults. Identifying the specific ways in which the governments in the six study sites. The data were dated mixing of land uses may affect physical activity has impor- between 2001 and 2005 depending on the site. An investiga- tant implications for planning and public health policy.
tor classified the land-use codes of each site into four mutu-ally exclusive categories: retail (including commercial), resi-dential, institutional, and office. For each parcel, whenever a retail use was present (regardless of other uses present in thebuilding occupying the parcel), the parcel was coded as retail Study Sample
use. If the parcel had institutional uses (but no retail), it was The Multi-Ethnic Study of Atherosclerosis (MESA) is a longi- coded as institutional use. If the parcel had industrial use (but tudinal study of cardiovascular disease among adults aged no retail or institutional), the parcel was coded as industrial 45– 84 years at six field sites in the U.S.: Baltimore MD, use. Land uses in Baltimore County were categorized into Chicago IL, Forsyth County NC, Los Angeles CA, New York only commercial and residential uses, as their data lacked the NY, and St. Paul MN.19 There was no clinically overt cardio- institutional and office designations. A second investigator vascular disease at cohort incept. The baseline visit for MESA, verified the classification and resolved disagreements. Appen- on which these analyses are based, took place between July dixes A–F, available online at www.ajpm-online.net, detail the 2000 and September 2002. The study was approved by the classification of land uses for each site.
IRBs at each site and all participants gave written informed Availability of retail in each neighborhood was calculated using the percentage of land area in parcels that containretail uses. By focusing on the area in parcels, transportation Walking Outcomes
features such as roads and railroads, water bodies, andutilities are excluded from the calculations. One drawback of A detailed interviewer-administered, semiquantitative ques- using parcel area is that it penalizes vertical development, for tionnaire adapted from the Cross-Cultural Activity Participa- example by treating a parcel with a four-story building in the tion Study20,21 was used to collect data on all forms of physical same way as a parcel with a one-story building. Entropy was activity, including leisure, household, work, and transporta- calculated using an established formula24 to assess the simi- tion activities at the baseline examination. The questionnaire larity in the proportion of the area in parcels devoted to 398 American Journal of Preventive Medicine, Volume 37, Number 5 retail, residential, institutional, and office land uses.7,9,14,24–26 were missing physical activity information, and 11 participants Entropy values range between 0 and 1, with 1 representing were excluded because of missing self-reported neighbor- equal proportion (25%) among the four uses in the neigh- hood environment data, leaving 5529 participants for borhood and 0 representing the presence of a single domi- Multinomial logistic models were used to analyze the Population density (hundreds of people/hectare) was mea- three-level categoric outcomes for each of the two outcome sured using population data from the U.S. Census at the variables (walking to places and walking for exercise) using block level and dividing them by the land area in parcels.
Stata 9.2. In all cases, no walking was used as the reference When a block was not fully contained within a neighborhood, category. Robust SEs with clustering were used to account for its population was assigned in direct proportion to the area of potential correlations among participants within sites.
the block contained within the neighborhood, which assumes None of the neighborhood objective and self-reported a uniform population density within each block. Road con- variables had particularly high colinearity (variance inflation nectivity was measured as the proportion of the neighbor-hood (the 200-m–radius circle area around each person’s factor Ͻ4), suggesting that they measure different constructs home) that is covered by a network buffer. The ratio varies or they measure similar constructs differently. Therefore, the between 0 and 1, with 0 meaning that none of the circle area neighborhood environment variables (objective and self- can be reached through the road network and 1 meaning that reported) were first entered one at a time into models that the entire circle can be reached through the street network, adjusted for individual characteristics (age, gender, educa- tion, race/ethnicity, and family income). Models also ad- Subjective measures of the neighborhood physical environ- justed for neighborhood road connectivity, because it may be ment were obtained from a questionnaire administered to associated with both land use and walking and could there- MESA participants that included items on ease of walking to fore confound the association of land use with walking. Next, places and having stores within walking distance. Responses all environment variables were entered simultaneously into a were reported on a 1 to 5 scale in which 1ϭstrongly agree and single model, adjusting for the same factors. Finally, Stata’s 5ϭstrongly disagree and are treated as continuous. These lincom command was used to provide a graphic representa- questions were part of an 11-item index shown to have high tion of the relationships of interest. All analyses were con- test–retest reliability (intraclass correlation coefficient [ICC]ϭ 0.88, 95% CIϭ0.79, 0.93).27 The questionnaire also includedtwo questions on the availability of YMCAs/YWCAs andon the availability of free community centers and schools open to the public, both reported as a binary variable (yes orno). The two variables were merged into a single variable Descriptive statistics for sociodemographic characteris- defined as the availability of institutional uses for physical tics and walking activity of participants are shown in activity and coded as a binary variable (yes if either is present, Table 1. Age of study participants ranged between 45 or no if neither is present). These two questions were part of and 84 years. Just over half of the sample (51.7%) were an eight-item index with high test–retest reliability (ICCϭ women; 40.1% of participants were non-Hispanic Cau- 0.85, 95% CIϭ0.75, 0.92).27 Item reliabilities were not re- casian, 25.9% non-Hispanic blacks, 22.1% Hispanics, ported. In responding to these neighborhoods’ environment and 11.9% Chinese. The median time of walking to items, participants were asked to refer to the area that was places was 150 minutes/week, and the median time for approximately a 20-minute or 1-mile walk from their home.
exercise walking was 90 minutes/week.
Sociodemographic Measures
Table 2 shows descriptive statistics for the measures of objective and self-reported land use and residen- Person-level data on age, gender, race/ethnicity, family in- tial development intensity. Neighborhoods had an come, and education were self-reported during the baselineMESA examination. Age was classified into four categories average population density of 153.2 people per hect- (45–54, 55– 64, 65–74, and 75– 84 years). Race and ethnicity are. Forty-one percent of respondents had no retail were classified as Hispanic, non-Hispanic white, non-Hispanic land uses in their neighborhood, and only one black, and Chinese. Family income was grouped into four quarter of the sample had Ն10.6% of the parcel area categories (Ͻ$20,000, $20,000 –$39,999, $40,000 –$74,999, in the neighborhood devoted to retail uses. The and Ն$75,000). Education was categorized as less than high entropy measure revealed substantial variability in school, high school/GED diploma, college, or graduate/ the land-use mixes around the homes of participants.
The percentage of participants agreeing or strongly Statistical Analysis
agreeing with the statements In my neighborhood it iseasy to walk to places and There are stores within walking Of the 6061 MESA participants at baseline that lived within distance of my home were 79.8% and 76.3%, respec- geographic areas for which land-use data were available, 237 tively. On average, 62.1% of participants reported were excluded because their address information could notbe connected to the road data set, likely the result of having schools or community centers with recre- geocoding error, road data error, or the fact that participants ational facilities available for free to the public or lived on very small roads not represented given the scale of YMCA/YWCAs available within a 20-minute walk the road data. An additional 284 were excluded because they Ն150 minute/week, after adjustment. Other land-use Table 1. Selected individual-level characteristics of
participants included in the analyses, MESA, 2000 –2002 characteristics (availability of institutional uses) were not related to walking to places. When all the exposures n
were included in a single model, density remainedpositively associated with walking to places for both Age (years)
walking levels relative to no walking, and the third and top quartiles of retail area were positively associated with more walking. Those with more stores within walking distance had higher odds of walking to places Ն150 minute/week, after adjustment. Entropy was not Race/ethnicity
Walking for Exercise
Education completed
Table 4 shows adjusted associations for the exercise walking outcome. When models were estimated for each exposure separately, density and all self-reported measures were related to exercise walking for Ͼ90 minutes/week, and ease of walking to places was the Family income (thousands $)
only variable related to some walking (Ͼ0 and Ͻ90 minutes/week), relative to no walking. For the mea- sures of land-use mixtures, the third and top quartiles of retail area and the top quartile of entropy were OUTCOMES
positively associated with walking Ͼ90 minutes/week.
Walking to places (min/wk)
When all the exposures were included in a single model, density, the top quartile of entropy, and ease of walking to places remained positively related to exer- Walking for exercise (min/wk)
cise walking for Ͼ90 minutes/week. Ease of walking to places remained significantly associated with some walking (Ͼ0 and Ͻ90 minutes/week).
Figure 1 portrays how density and retail uses were aPercentages do not add to 100 because of rounding.
jointly related to the probability of walking to places bA measure of colinearity among variables.
based on the parameters estimated, while holding MESA, Multi-Ethnic Study of Atherosclerosis; NA, not applicable; constant all continuous variables at their means and allcategoric variables at their modes. The values of densityvary from the 5th to the 95th percentile in the data. The Walking to Places
values for retail represent the indicator variables in Adjusted associations of the objective and self-reported quartiles used in the models. The probability of walking land-use/intensity variables with walking to places are to places for Ͻ150 minutes/week relative to no walking shown in Table 3. When models were estimated for increased from 75.7% to 98.2% when density and retail each exposure separately, higher levels of population increased jointly from the 5th to the 95th percentile.
density and the highest quartile of the percentage of For similar changes in density and retail, the probability parcel area devoted to retail were each associated with of walking for exercise for Ͼ150 minutes/week relative higher levels of walking to places after adjustment for age, to no walking increased from 66.4% to 95.2%.
gender, race/ethnicity, education, income, and streetconnectivity. Being in the top quartile (Ն10.6% of par- cel area in retail) relative to the baseline category ofhaving no retail was associated with 1.81 higher odds of In a diverse population sample of middle-aged and some walking (Ͼ0 but Ͻ150 minutes/week) and 2.57 older adults, objective and self-reported measures of higher odds of walking to places Ն150 minute/week.
land use and residential density were consistently asso- None of the entropy measures was associated with walking ciated with higher odds of walking. In adjusted models examining each measure separately, higher population For self-reported measures, people reporting that it density and a higher percentage of parcel area devoted was easier to walk to places had higher odds of walking to retail land uses were each associated with higher to places, and those reporting more stores within odds of walking to places and walking for exercise.
walking distance had higher odds of walking to places Weaker evidence was found for self-reported measures 400 American Journal of Preventive Medicine, Volume 37, Number 5 Table 2. Objective and self-reported land-use/intensity characteristics around the home of participants included in analyses,
n
OBJECTIVE/DERIVED MEASURES
(200-m buffer unless noted)
Density (hundreds of people/hectare)
% parcel area devoted to retail use
Entropya
Proportion of 400-m buffer from home accessible via SELF-REPORTED MEASURES
Easy to walk to placesb
3ϭNeutral (neither agree nor disagree) Stores within walking distance (20 min)b
3ϭNeutral (neither agree nor disagree) Availability of institutional uses (schools, YMCA/
YWCAs) within walking distance (20 min)
aEntropy was calculated among residential, institutional, retail, and office uses using the formula presented by Cervero and Kockelman.24 For parcels with mixed uses, if they contained any retail uses they were considered retail use. Those having any office uses (but no retail) were considered office uses. Any institutional uses (but no retail or office uses) were considered institutional uses. Higher values represent a more even proportion of area devoted to each land use.
bMeasured with a Likert-type scale ranging between 1 and 5, with 1ϭstrongly agree and 5ϭstrongly disagree. Scale shown in table and used in analyses is reversed so that higher values mean more support for walking, consistent with the objective measures.
MESA, Multi-Ethnic Study of Atherosclerosis of ease of walking, presence of stores, and availability of to older-age adults. Although measures of neighbor- hood perceptions were limited, the results suggest that In models that included both objective and self- objective features of neighborhoods may influence reported measures, higher population density and residents’ behaviors independently of their percep- higher percentage of parcel area devoted to retail uses tions. Interestingly, perceived presence of stores within remained significantly associated with higher odds of walking distance remained significant for the highest walking to places. The estimates for the percentage of level of walking to places even when objective measures parcel area in retail uses suggest a dose–response relationship between exposure to retail uses and walk- Density was the measure most consistently related to ing to places. In addition, higher density, being in the walking. Few studies have included as much variation in top quartile denoting the most proportional distribu- density as the present study, and fewer have focused on tion of land among various uses, and self-reported ease middle-aged and older adults. The strength of density of walking to places remained associated with walking in predicting walking activity has been previously no- for exercise after adjustment for other objective and ted,9,28,30–32 but studies of older adults remain rare.
The results suggest that the importance of density for By focusing on land use and residential density in six physical activity promotion goes beyond the connectiv- diverse urbanized areas in the U.S., this study extends ity and access to destinations that density brings.
prior evidence9,14,28,29 regarding the importance of Figure 1, showing the joint contribution of density land use and residential density for walking in middle- and retail to explaining the probability of walking to Table 3. Adjusted OR (95% CI) of walking to places (in three levels) associated with neighborhood land-use and density
variables, MESA, 2000 –2002 (nϭ5529) Models for each exposure separatelya,b
Full model with all exposures includeda,b
Level 2 vs Level 1
Level 3 vs Level 1
Level 2 vs Level 1
Level 3 vs Level 1
OR (95% CI)
OR (95% CI)
OR (95% CI)
OR (95% CI)
OBJECTIVE/DERIVED MEASURES
Density (hundreds of people/hectare)
1.31 (1.14, 1.51)
1.41 (1.21, 1.65)
1.28 (1.12, 1.46)
1.34 (1.16, 1.55)
% parcel area devoted to retail use
1.19 (1.02, 1.38)
1.22 (1.02, 1.46)
1.81 (1.12, 2.93)
2.57 (1.28, 5.15)
1.44 (1.19, 1.76)
1.73 (1.26, 2.38)
SELF-REPORTED/PERCEIVED
MEASURES
1.13 (1.03, 1.24)
1.26 (1.06, 1.50)
1.29 (1.07, 1.55)
1.09 (1.01, 1.18)
aWalking to places measure categorized into level 1 (none); level 2 (Ͼ0 and Ͻ150 min/wk); and level 3 (Ն150 min/wk) bAdjustment factors are age, gender, education, race/ethnicity, family income, and proportion of 400-m buffer from home accessible via roads.
Robust SEs with clustering on each site are shown. All objective measures are calculated for a 200-m radius around each participant’s home.
Bolded coefficients are significant at a 95% level of confidence.
MESA, Multi-Ethnic Study of Atherosclerosis places, has two salient characteristics: nonlinearity and even when density and retail use are already at consid- high uncertainty. First, the figure graphically depicts erable levels, as they move toward the higher percen- that the benefits of walking, owing to increased density tiles of their respective distributions. Second, the CIs and the inclusion of retail land uses, can materialize suggest that even though the probability of walking to Table 4. Adjusted OR (95% CI) of walking for exercise (in three levels) associated with neighborhood land-use and density
variables, MESA, 2000 –2002 (nϭ5529) Single model with all exposures
Models for each exposure separatelya,b
includeda,b
Level 2 vs Level 1
Level 3 vs Level 1
Level 2 vs Level 1
Level 3 vs Level 1
OR (95% CI)
OR (95% CI)
OR (95% CI)
OR (95% CI)
OBJECTIVE/DERIVED MEASURES
Density (hundreds of people/hectare)
1.09 (1.08, 1.11)
1.06 (1.04, 1.09)
% parcel area devoted to retail use
1.34 (1.07, 1.69)
1.49 (1.06, 2.10)
1.29 (1.08, 1.54)
1.19 (1.05, 1.34)
SELF-REPORTED/PERCEIVED
MEASURES
1.12 (1.07, 1.18)
1.30 (1.20, 1.41)
1.14 (1.08, 1.20)
1.23 (1.14, 1.32)
1.18 (1.07, 1.29)
1.18 (1.05, 1.32)
aWalking for exercise or leisure measure categorized into level 1 (none); level 2 (Ͼ0 and Ͻ90 min/wk); and level 3 (Ն90 min/wk) bAdjustment factors are age, gender, education, race/ethnicity, family income, and proportion of 400-m buffer from home accessible via roads.
Robust SEs with clustering on each site are shown. All objective measures are calculated for a 200-m radius around each participant’s home.
Bolded coefficients are significant at a 95% level of confidence.
MESA, Multi-Ethnic Study of Atherosclerosis 402 American Journal of Preventive Medicine, Volume 37, Number 5 hold is surrounded by walkable nonresidential destina-tions yields a disproportionate distribution of land usesin an environment supportive of walking to places. Theevidence provided here, in addition to theoretic limi-tations, and the difficulty in correctly interpreting andcommunicating its meaning, suggests that cautionshould be used in applying entropy as a neighborhoodenvironmental measure in future studies.
Compared to other studies, the neighborhood-area definition of a 200-m circle is small. Measures drawnfrom circles of 400-m and 800-m radii were tested byexamining model fit using the Bayesian informationcriterion (BIC). It has been suggested33 that evidencefavoring one model over another is weak, positive,strong, or very strong if the absolute difference in BICfor two models is 0 –2, 2– 6, 6 –10, or Ͼ10, respectively.
With the exception of the single model with all expo-sures explaining exercise walking that exhibited weakevidence favoring the 400-m buffer, all models withexposures measured for the 200-m circle were stronglyor very strongly favored over larger circles. In contrast,another study13 found no pattern in model fit at variousbuffer sizes.
One explanation for the results favoring the smallest circle is that for an older population, proximal landuses may be more relevant than uses that are moredistant. Another explanation is that the retail andentropy measures are neighborhood-scale dependent, Figure 1. Adjusted predicted probability and 95% CI of
a phenomenon known as the modifiable areal unit walking to places relative to no walking by percentile of problem.34 As the neighborhood area definition in- neighborhood density and percentage land area devoted to creases, neighborhood heterogeneity increases, thereby retail uses, Multi-Ethnic Study of Atherosclerosis (MESA), decreasing variation in the entropy and retail measures.
Note: Walking to places measure categorized into Level 1 Limitations of this study include the use of self- (none); Level 2 (Ͼ0 and Ͻ150 min/wk); and Level 3 (Ն150 reported walking, the reliance on land-use information min/wk). Level 1 is the reference category. Adjustment collected from diverse sources, and potential residual factors are age, gender, education, race/ethnicity, family confounding. Bias caused by the cross-sectional design income, and proportion of 400-m buffer from home accessi- is also a possibility, because people who enjoy walking ble via roads. Robust SEs with clustering on each site are are more likely to move to areas that support walking.
Mis-specification of the relevant geographic area couldalso have affected the results.
places increases when density and retail increase jointlyfrom their 10th percentile to their 80th percentile, the uncertainty around the estimates is such that the pre-dicted change in walking to places is no different from Taken together, the results of this study provide sup- port for the relationship of retail, land-use mix, and Results for the entropy variable were not entirely residential density with walking behaviors. The findings consistent. The highest quartile of entropy was associ- support calls for policies that guide new development ated with walking for exercise in models adjusted for and changes in already-developed areas to intensify individual-level characteristics. However, entropy was density and mixed land uses. Further, these policies may not associated with walking to places. This contrasts be more effective in areas with established levels of with other studies9,29 and may be the result of measure- development density and retail land uses, rather than in ment differences. Although mean entropy in this study areas with very low density and residential-only land uses.
is almost identical to values in other studies,9,24 the Prospective studies and evaluation of natural experiments figures cannot be compared directly. Further, the the- can further inform this discussion. The relationships of oretic reasons to expect similarity in the proportion of neighborhood characteristics with walking underscore land devoted to different uses to be related to walking calls for collaborative efforts among traffic engineers, city are unclear. An instance in which a residential house- planners, and health professionals to understand how urban areas can be improved to address the welfare of 14. Frank LD, Andresen MA, Schmid TL. Obesity relationships with commu- nity design, physical activity, and time spent in cars. Am J Prev Med2004;27(2):87–96.
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404 American Journal of Preventive Medicine, Volume 37, Number 5

Source: http://blog.uwinnipeg.ca/ChristopherLeo/SprawlHealthWalk.pdf