built environment

Study: Building walkable communities can change behavior for the better

kkrisberg — Fri, 30 Jan 2015 16:19:16 +0000

Study: Building walkable communities can change behavior for the better

It’s not unusual for studies on community walkability to face the perplexing question of self-selection. In other words, people who already like to walk end up moving to walkable communities and so those communities naturally have higher physical activity rates. In even simpler terms, it’s about the person, not the environment. However, a new study finds that walkable community design does influence healthy behavior — even among people with no preference for walking in the first place.

Published in December in a supplement of the Preventive Medicine journal, the study examined changes in residents’ physical activities, social interactions and neighborhood cohesion after they moved into a walkable community in Austin, Texas, known as Mueller. (Disclosure: I live in Austin and frequently walk around the parks and neighborhoods of Mueller.) Mueller is a 711-acre community about five miles from downtown that will eventually accommodate 10,000 residents and 10,000 employees when it’s fully complete in 2018. It’s a compact development that’s home to residences, retailers, complete sidewalks, community gathering areas and lots of wide-open green space. To conduct the study, researchers surveyed more than 400 residents between 2013 and 2014 on their activities and perceptions of Mueller as well as their experiences before moving to Mueller.

Xuemei Zhu, the study’s lead author and an associate professor in the Department of Architecture at Texas A&M University, said Mueller represents somewhat of a rare opportunity for researchers. While planned walkable communities are growing in number, she said their popularity is still limited. And even though Mueller is still fairly new, residents have lived there long enough to experience a personal impact.

“We wanted to study how the built environment influences people’s behaviors, but it can be rare to have that type of opportunity,” Zhu told me. “We see the potential of involving more walkable and compact environments in making people healthier and making the environment more sustainable.”

In studying the Austin neighborhood, Zhu and her fellow researchers found that physical activity significantly increased after moving to Mueller among the entire study sample, except among those who had previously been sufficiently physically active. Overall, residents reported a 40 percent average increase in walking or biking after moving to Mueller. Specifically, 65 percent of residents said they experienced increased physical activity post-move, while 48 percent said their health had improved. The number of residents who took part in at least 30 minutes of moderate physical activity five or more days per week increased from about 34 percent to nearly 46 percent after moving to Mueller. In addition, residents reported spending significantly less time in their cars, which can be a boon for local air quality.

Digging even deeper, the study found that residents who previously lived in less-walkable communities reported significant increases in physical activity, while those who came from highly walkable communities did not report big changes after moving to Mueller. In particular, residents who came from medium-, low- and very low-walkability communities all reported nearly an hour of additional physical activity per week after moving to Mueller. Perhaps most notably, people who reported low levels of physical activity pre-Mueller experienced significantly increased levels of physical activity after moving to Mueller. In addition to the physical activity effects, residents also reported feelings of heightened neighborhood cohesion after moving to the more walkable neighborhood.

Zhu told me that while she wasn’t entirely surprised to uncover physical activity impacts, she was surprised to see such a positive impact on social interaction and cohesion. In fact, she said the social cohesion impacts might be even more dramatic than the physical activity effects, as positive feelings about social cohesion significantly increased throughout the entire study sample and not just in particular subgroups. To illustrate that finding, Zhu noted that while many of the Mueller homes have either no backyard or very small backyards, residents didn’t seem to mind — they were happy to sacrifice the backyard space in exchange for heightened social interaction with their neighbors.

“In many instances, (residents) mentioned how great the neighborhood support is...and that’s always very important for health conditions, both mentally and physically,” she said. “While we cannot claim (a direct association) right now, I would guess that social interaction acts as a mediator and actually encourages people to be more active. It’s mutually beneficial — if you’re more active, you have more social interaction, and if you have more friends in the neighborhood, you’re more likely to go out and be active.”

In the future, Zhu and her colleagues hope to follow Mueller residents over a longer time period as well as reach out to people before they move to Mueller to more precisely gauge the effects of living in a walkable community. They also hope to learn more about the effects on lower-income families, as Mueller was specifically designed as a mixed-income neighborhood. Still, she said this preliminary study does support the notion that designing walkable built environments can produce healthier behaviors, which could be a real boost for public health efforts to increase physical activity and curb the costly obesity epidemic.

“We need to further bridge urban planning and public health efforts,” Zhu said. “This is an approach that may be more likely to work for a majority of the population and is easier to sustain. It’s a win-win solution.”

To learn more about the study, visit Preventive Medicine or click here for a news release about the research.

Kim Krisberg is a freelance public health writer living in Austin, Texas, and has been writing about public health for more than a decade.

kkrisberg Fri, 01/30/2015 - 11:19

Pedestrians, bicyclists at disproportionate risk of being killed by a distracted driver

kkrisberg — Mon, 04 Nov 2013 09:13:18 +0000

Pedestrians, bicyclists at disproportionate risk of being killed by a distracted driver

It takes time to change social norms, so it'll probably take many, many years until it's as socially unacceptable to text or use a cell phone while driving as it is to start the engine without first buckling a seat belt. In the meantime, researchers say, smart policies are needed to address the increasing share of pedestrian and bicyclist deaths attributed to distracted driving.

According to a new study published in Public Health Reports, the rate of distracted driving-related fatalities per 10 billion vehicle miles traveled went up from 116.1 in 2005 to 168.6 in 2010 for pedestrians and from 18.7 in 2005 to 24.6 in 2010 among bicyclists. However, distracted driving-related deaths among motorists decreased over the same time period — a trend that study authors said mirrored overall motor vehicle fatalities and may be attributed to safer vehicles. Unfortunately, cyclists and pedestrians don't have such protection on the road. In fact, distracted drivers were 1.6 times as likely as nondistracted drivers to mortally hit a pedestrian at marked crosswalks and about three times as likely to hit a pedestrian while on a road shoulder.

"Distraction is becoming more of an issue over time, so it makes sense that we'd see these increases," said study co-author Fernando Wilson, associate professor in the College of Public Health at the University of Nebraska Medical Center. "That wasn't a surprise, but I think the percentage increase was striking, particularly for pedestrian fatalities."

In conducting the study, Wilson and his colleagues used the National Highway Traffic Safety Administration's definition of distracted driving, which can range from texting or using a GPS to eating or drinking, and gathered data from the Fatality Analysis Reporting System from 2005 to 2010. In addition to reporting on fatality rates, the study also examined demographic characteristics among those most at risk of being hit by a distracted driver. Pedestrians involved in distracted driving crashes were mostly male, white and between ages 25 and 64; bicyclist victims were also more likely to be male and white. More than 80 percent of pedestrian victims were hit in a metro area as were more than 77 percent of bicyclists. The majority of both pedestrians and bicyclists included the study were hit outside a crosswalk. Study authors Wilson, Jim Stimpson and Robert Muelleman write:

Mounting evidence links the use of electronic devices with increased traffic deaths and injuries. Even though traffic deaths are declining, deaths from distracted driving are rising, with one study attributing much of this increase to texting volume, which surpassed 100 billion monthly text messages in 2008. However, there are many potential causes of distraction other than electronic devices that threaten roadway safety. Most of this research has examined aggregate fatalities and injuries from distracted driving crashes, but little is known about the characteristics of victims killed in these crashes despite extensive research on predictors of pedestrian injuries.

While the current data on distracted driving is surely enough to act on, Wilson told me the numbers are probably under-reported. There's inconsistency across states and agencies when it comes to reporting the specific causes of distracted driving, and it really comes down to the individual law enforcement officer and whether he or she documents what kind of distraction — a phone call, a text, GPS — was involved in a crash, he said. Also, Wilson added, without quality data it makes it harder to evaluate the effectiveness of interventions.

"Improvement in data collection would definitely be helpful for finding solutions, but that doesn't mean states or localities have to wait to actually create policy," Wilson said. "I don't think anyone is going to argue that the problem is not there and not significant...People may quibble over the numbers or the types of distractions, but I think that everyone agrees that distracted driving is a major threat to road safety."

Right now, the evidence is mixed as to the success of laws that target distracted driving. For example, Wilson said, several studies show that years after the passage of laws that ban texting or cell phone use while driving, such rates go back up to before the law's enactment or don't change at all.

"These policies really need a sustained commitment by law enforcement and sustained media attention to maintain awareness or the effect dissipates," Wilson said. "The policy environment is still a work in progress."

However, the study notes that there is "growing evidence that changing the built environment, which includes traffic engineering and roadway characteristics, is an effective, sustainable approach to protect pedestrians and bicycle riders." Wilson added that although built environment changes can bump up against funding restraints, it's definitely an option policymakers should consider when trying to save lives on the road.

"We want to reach anyone who could glean insight from the study and might be able to use the results in some way, whether that's advocacy for reshaping the built environment, installing more bike lanes, creating marked crosswalks or passing laws to curb distracted driving," he told me. "It's going to take time to reshape social norms to make (distracted driving) unacceptable."

To download a full copy of the Public Health Reports study, click here.

Kim Krisberg is a freelance public health writer living in Austin, Texas, and has been writing about public health for more than a decade.

kkrisberg Mon, 11/04/2013 - 04:13

As someone who cycles to work every day, this is an important topic to me. I have to wonder, though, how close we are to diminishing returns; 187.3 deaths per 10,000,000,000 miles traveled seems awfully close to random noise. Will adding new regulation actually decrease that number?

It sounds cold, but at some point we have to accept the fact that if we want the benefits/efficiency of cars, bicycles, and pedestrians sharing the same surfaces, we have to accept that there is going to be some level of fatalities as those three very different transportation norms interact. We can't legislate away all dangers.

I think it should be socially unacceptable to use a cell phone when driving. in fact it is beginning to be so in the UK.
However i don't understand why it should be so not to wear a seat belt? Sure its a legal requirement in the uk but with cell phones you endanger others, which is a social gaffe. but not wearing a seat belt you just endanger yourself. Why is that an issue?
Or am i missing something?

Designing better health: New EPA report links development and human health

lborkowski — Fri, 21 Jun 2013 12:30:05 +0000

Designing better health: New EPA report links development and human health

by Kim Krisberg

When most of us pass by a new high-rise or drive down a new road, we rarely think: Did the builders and planners consider my health? However, a new report from the U.S. Environmental Protection Agency offers evidence that certain types of land use and transportation decisions can indeed limit the human health and environmental impacts of development.

Released in mid-June, the publication is a revised and updated version of an EPA report initially published in 2001. Agency officials said the report was particularly timely as the nation's built environments are quickly changing — in fact, the report states that “researchers have estimated that as much as two-thirds of the development that will exist in 40 to 45 years does not exist today, meaning that decisions we make about how and where that development occurs could significantly affect our health and the health of the environment.” The report goes on to say:

Patterns of development, transportation infrastructure, and building location and design — the built environment — directly affect the natural environment. Development takes the place of natural ecosystems and fragments habitat. It also influences decisions people make about how to get around and determines how much people must travel to meet daily needs. These mobility and travel decisions have indirect effects on human health and the natural environment by affecting air and water pollution levels, the global climate, levels of physical activity and community engagement, and the number and severity of vehicle crashes.

Just a couple of the consequences of how we build and design our communities listed in the EPA publication: At least 850,000 acres of lakes, reservoirs and ponds and 50,000 miles of rivers and streams are estimated to be contaminated by stormwater runoff. And even though advancements in technology have reduced individual car emissions (emissions that reduce air quality and complicate respiratory disease), the substantial increase in car travel — often the only practical way for people to travel to and from daily destinations — has offset any potential gains from emission-reducing technology.

The report also notes that while data is incomplete as to the relationship between the built environment and obesity and physical activity levels, a majority of studies have found that community design does play a role in people's decisions to exercise. In fact, even the CDC's Guide to Community Preventive Services recommends design and land-use policies that encourage and support physical activity. And a 2012 Alliance for Biking & Walking report found that $11.80 in benefits can be gained for every $1 invested in bicycling and walking infrastructure.

In a news release announcing the new report, EPA Acting Administrator Bob Perciasepe said: “This report will be useful for communities across the country looking to make smart development decisions. Whether it’s housing, transportation, or environmental issues, this report can help communities protect public health and the environment by avoiding harmful development strategies.” The report notes that strategic changes in how we design and plan our communities can make a difference.

For example, doubling residential density can reduce reliance on vehicles, which in turn reduces air pollution and increases the likelihood that people choose physically active travel means; making transportation decisions that include safe biking and walking options will also encourage physical activity; and green building materials and infrastructure can improve indoor air quality and limit negative impacts on water quality.

Of course, public health professionals have long known about and focused on the effects of our environments on health. However, there is a growing movement to integrate health considerations into transportation and community design as well as to strengthen the linkages between public health workers and transportation and urban planners. To learn more about those topics, visit APHA, Transportation for America or the Smart Growth Network.

To download a copy of EPA's new report, "Our Built and Natural Environments: A Technical Review of the Interactions Between Land Use, Transportation, and Environmental Quality," click here.

Kim Krisberg is a freelance public health writer living in Austin, Texas, and has been writing about public health for more than a decade.

lborkowski Fri, 06/21/2013 - 08:30

Report on chemical-asthma links a useful resource for workers at risk

lborkowski — Fri, 21 Sep 2012 14:29:40 +0000

Report on chemical-asthma links a useful resource for workers at risk

by Kim Krisberg

It really is a chemical world, which is bad news for people with asthma.

According to a recent report released in August, at this very moment from where I write, I'm fairly surrounded by objects and materials that contain chemicals that are known or suspected asthmagens — substances that can act as asthma triggers if inhaled. There's formaldehyde (it's in office furniture, wood flooring, curtains and drapes); maleic anhydride (it's in interior paint and tile flooring); hexamethylene diisocyanate (it's in metal storage shelving and decorative metal); and diisodecyl phthalate (it's in horizontal blinds). In just two items found in practically all indoor environments — paints and adhesives — there are 75 substances linked to the chronic respiratory disease. It is not a stretch to say that we are all swimming in a world built with the help of chemicals about whose long-term human health effects we know too little.

The new report, compiled by the architecture and design firm Perkins+Will on behalf of the National Institutes of Health, lists nearly 400 substances typical to our built environments — the places we live, work and play — that are known or suspected asthmagens. One section of the report addresses asthmagens that are common in building design and construction, while another describes asthmagens found in a variety of environments and products (e.g., baking ingredients, agricultural inputs and personal care products). The purpose of the report is "raising awareness of the connection between health and buildings while identifying existing sources of information so that healthy buildings will result," states a news release. However, a quick glance through the report's long lists of hard-to-pronounce chemicals and the ubiquitous and prolific items they're used in made me wonder: How can this list be put into action to actually make a difference?

Ken Rosenman, professor and chief of the Division of Occupational and Environmental Medicine at Michigan State University, says it seems mostly beneficial for workers — "to me, it's most useful for (workers) more so than for us sitting in our offices or at home."

"For example right now, I'm sitting on a chair that contains diisocyanates," Rosenman told me. "But there's no real risk to me of developing asthma from it. The risk is to the guys manufacturing it."

According to the American Academy of Allergy, Asthma & Immunology, occupational asthma is the most common work-related lung disease in developed nations, with up to 15 percent of U.S. asthma cases related to a person's job. OSHA estimates that about 11 million workers in a variety of job settings and occupations are exposed to substances known to be linked with occupational asthma. However, the real rate of occupational asthma is likely way undercounted — "you wouldn't find anybody who'd say that's an accurate estimate," said Katherine Kirkland, executive director of the Association of Occupational and Environmental Clinics. Right now, only five states officially track work-related asthma. Both Kirkland and Rosenman said the report could be a useful and educational resource for physicians, many of whom are simply unfamiliar with occupational-related asthma and its contributors.

"The average clinician never asks what people are exposed to at work," Kirkland told me. "This would be routine at occupational health clinics...but it's not something the average physician would even know to ask about."

Occupational exposures to asthmagens truly run along the spectrum. The Perkins+Will report notes that an average carpenter comes in contact with at least 13 substances linked to asthma on a daily basis; agricultural workers with six substances; dentists with 14 substances; pharmaceutical or chemical industry workers with 34 substances; and health care workers with five substances. These numbers are in addition to the 75 asthma-related substances common to most indoor environments, the report states. The report's complete list of 374 substances and the occupations most exposed ranges from ammonium persulphate (common among factory workers and hairdressers) to soy flour (common among bakers) to triplochiton scleroxylon, otherwise known as African Maple (common among carpenters).

Specifically, Rosenman said there may be some healthier substitutes that builders and manufacturers could use instead. However, a more practical way to reduce the impact is to reduce workers' exposure through better safety practices and controls, such as providing appropriate ventilation and, if that isn’t sufficiently effective, respiratory equipment.

"Just because it's an asthmagen doesn't mean it'll cause asthma in everyone exposed," said Kirkland. "On the other hand, if you know something is an asthmagen, you can take preventive measures to reduce harm. We're not saying ban everything that's an asthmagen...but be aware and try to mediate the risk as best as possible."

Rosenman noted that the report is a reminder of the enormous complexity of our built environments and the items we come in contact with on a daily basis. We use about 80,000 chemicals regularly in our society, he said, a large number of which have never been subjected to toxicology tests or studies to determine their health impacts.

"People think that if I can buy it in my local hardware store then it must be safe, there must be somebody who's looked at it," he said. "But that's not the case."

Asthma at home
Asthma may be the quintessential public health problem. Its severity and progression ebbs and flows with our environments, and its management requires both a clinical and public health-based approach to be truly effective. According to the Centers for Disease Control and Prevention, the numbers of people with asthma have grown by the millions in the last decade: In 2009, about 25 million U.S. residents had asthma, compared to about 20 million in 2001, with the greatest rise among black children. Health care costs related to asthma totaled about $56 billion in 2007.

About 40 percent of asthma cases can be linked to housing conditions, says Rebecca Morley, executive director of the National Center for Healthy Housing, though often the factors are related to pests, mold and indoor exposure to secondhand tobacco smoke. (These are often the contributors in which public health workers can make a critical difference — providing education and empowering people with the tools to manage asthma on their own and prevent serious respiratory complications through changes in their environments.) Still, Morley said, building materials present risks as well.

"History tells us that with building materials, oftentimes we don't recognize the full extent of problems until much later on," she said, pointing to asbestos, lead, arsenic and formaldehyde. "All of these things were put in building materials for durability and maintenance but they were never really tested for health effects, so it stands to reason that we have a whole body of chemicals that have a whole set of health effects that have never been explored."

(For more on the benefits of reforming the nation's out-of-date chemical safety laws, read this 2011 article from the Pump Handle.)

Morley said that builders and contractors in markets where there's demand for healthier materials might be sensitive to the Perkins+Will report; but otherwise, it might not make much of a difference unless new regulations come down from policy-makers.

"We really want to drive health considerations into the decision-making process when manufacturers and builders are selecting their materials," she said. "In the past, that's never really been a factor — health and environmental concerns have been distance concerns for most builders unless their part of a market that positions itself as green and healthy.

"Builders are mostly driven by consumer demand, so the important thing for families and people to understand is the contribution of their homes to their health and demand better, healthier products."

To download the full Perkins+Will report, "Healthy Environments: A Compilation of Substances Linked to Asthma," click here.

Kim Krisberg is a freelance public health writer living in Austin, Texas, and has been writing about public health for the last decade.

lborkowski Fri, 09/21/2012 - 10:29

Healthy behaviors and where the money goes

lborkowski — Thu, 07 Jun 2012 16:59:42 +0000

Healthy behaviors and where the money goes

Via Ezra Klein, here's a striking infographic from the Bipartisan Policy Center comparing what makes us healthy to how we as a nation spend our health dollars:

Infographic from the Bipartisan Policy Center

As it illustrates, behaviors are major contributors to our health status, but a tiny fraction of US health spending goes to encouraging healthy behaviors like physical activity.

The Bipartisan Policy Center report Lots to Lose: How America's Health and Obesity Crisis Threatens our Economic Future offers several recommendations for improving nutrition and physical activity in the US. In addition to recommendations for schools and childcare providers (start encouraging physical activity at an early age, and require 60 minutes of physical activity during each school day), it has several recommendations for communities. One acknowledges that local government funds are tight, but suggests partnerships to increase the use of limited spaces for play and exercise:

In communities that lack safe, adequate places for children, youth and adults to exercise and play, or where schools don't have the facilities to support physical activity programs, "joint use" agreements provide a mechanism to enable the shared use of public facilities. Typically, this type of agreement would be struck between two government entities, such as a school district and a city or county. Joint use agreements have been successfully used in a number of locales to expand the sport and recreational opportunities available to students and members of the community. A variety of other low-cost options and public-private partnerships have also been used to promote healthy activity at the community level -- a good example are the various walking initiatives, such as Everybody Walk and Get Fit, that have been launched in neighborhoods and at schools across America.

And there's this recommendation, which will sound familiar to people in public health:

Healthy Communities Recommendation #8: Local governments should use the planning process to change the built environment in ways that promote active living.
Growing numbers of cities and towns are using the planning process and zoning codes to shape the built environment in ways that promote walking and bicycling, help residents stay connected, and improve quality of life. In many cases, mayors and county and city council representatives are working with architects and designers and with planning, transportation and public health departments to create healthier buildings, streets, and urban spaces based on the latest academic research and best practices. As an alternative to imposing new requirements, some cities have removed or changed old zoning codes that work against the goal of encouraging healthier, more active living. Other cities have incorporated physical activity guidelines into their construction codes and adopted policies that support outdoor play and exercise. These include offering incentives to designers and developers to build in ways that encourage walking, bicycling, and active transportation and recreation.

I've seen a lot of this going on in DC over the past few years. As the city has torn up our streets to upgrade water and sewer lines, they've rebuilt them with better sidewalks and new bike lanes. And Christine Green at Greater Greater Washington describes some of the community initiatives in the DC metro area:

Prince George's County is taking action through a partnership of towns within the county. The Port Towns Community Health Partnership has a policy development team focused specifically on the built environment and nutrition policy to improve options for active living and healthy eating.

The group, which includes the towns of Bladensburg, Colmar Manor, Cottage City, and Edmonston, included a community health and wellness section in the Port Towns sector plan with the goals of providing safe places to walk and exercise and access to nutritious foods. The group is following through on sector plan recommendations to formalize a wellness opportunity zone as part of the zoning code. This would include changes in the built environment, access to healthier foods, and improved environmental stewardship.

Across the Potomac, the Fairfax County Health Department established the Partnership for a Healthier Fairfax, a group of community members and organizations concerned with public health. The Partnership created an environment and infrastructure strategic issues team as one of five teams who will make recommendations for improving health in Fairfax County. The first focus is a on local policy. The team is doing a scan of policies, including transportation and land use, that could be modified to promote a healthier and safer physical environment.

When planning is done poorly, without sufficient consideration for active transportation and exercise opportunities, the consequences can be particularly severe for those who have few other options. In a "Narrative Matters" piece in the journal Health Affairs, doctor Cameron Page writes about one of his patients whose health suffered after his community lost park space for pickup soccer games.

P, a Hispanic man in his early 40s, told Dr. Page that for years he'd been in the habit of playing pickup soccer games at Macombs Dam Park in the Bronx. But construction of the new Yankee Stadium resulted in the loss of that space. The city had pledged to replace every acre of lost parkland, but Dr. Page learned that it classified a brick walkway and a parking garage topped with artificial turf as parkland, and moved the remainder of the park half a mile away on the other side of a pedestrian-unfriendly expressway. The new park had tennis courts and bricks, but no grass on which to play soccer.

For P, the loss of the soccer field meant worse health. He gained 40 pounds and his back started hurting. Page writes:

We tried to come up with an alternative exercise plan, but P loved soccer. After a few wasted minutes discussing Zumba and Pilates, I gave up. I told him to try to find another soccer field or start walking to work.

...In the summer of 2010, when I finished my medical residency and said goodbye to P, there was still no place for him to play soccer. He was still forty pounds overweight, he’d developed hypertension, and his LDL (the measure of so-called bad cholesterol) had increased from a well-controlled 100 to a troubling 160.

... P isn’t playing soccer in the shadow of Yankee Stadium anymore. He might not be playing soccer at all. And there’s not much I can do about that; I can’t write a prescription that gives him access to a local park. The challenge of the obesity epidemic extends beyond the doctor’s office to urban planners, city council members, and—in a democracy like ours—all of us as citizens. In a sense, when it comes to protecting green space, we are all each other’s doctors.

It does take resources (financial and otherwise) to ensure that communities have sidewalks, bike lanes, parks, and other elements that make it easy for residents to engage in regular physical activity. Relatively small investments can yield impressive activity improvements, though. If we could channel a small fraction of our $2.6 trillion in annual national healthcare spending into improving the built environment, it could do a lot to improve our overall health and quality of life.

lborkowski Thu, 06/07/2012 - 12:59

Light Rail and Obesity in one NC City

lborkowski — Wed, 01 Sep 2010 17:26:59 +0000

Light Rail and Obesity in one NC City

As we try to figure out how to curb an unhealthy increase in obesity, one of the factors under consideration is the built environment. Those who in live in places where few destinations are within walking/biking distance, public transit is limited, and the environment is unfriendly to pedestrians and cyclists may find it harder to get the recommended amount of physical activity. Studying the built environment's effect on obesity is challenging, though. People who live in pedestrian-friendly areas with good public transit may be more likely to get enough activity and less likely to be obese than their counterparts in car-dependent places, but that doesn't demonstrate causation. What if people who hate physical activity naturally gravitate toward auto-dependent areas, and walkers move to places where it's easy to get around on foot?

This is why I was excited to see a study by researchers from the University of Pennsylvania, Drexel University, and the RAND Corporation that takes advantage of a natural experiment to study causality (via Ryan Avent). It was published in the August 2010 issue of the American Journal of Preventive Medicine, and the full text is available for free online.

The natural experiment took the form of a new light rail transit (LRT) line in Charlotte, NC. Researchers conducted two phone surveys with residents living within a one-mile radius of the new line; participants were first interviewed 8-14 months before the LRT opened, and again 6-8 months after the system became operational. The study ended up with a total of 489 respondents who lived in the area and agreed to be interviewed at both times.

Participants were asked for their height and weight (which was then used to calculate BMI) and whether they met weekly recommended physical activity (RPA) through walking. The American College of Sports Medicine and American Heart Association recommend vigorous activity 3 times a week, â¥20 minutes a time; or walking 5 times a week, â¥30 minutes a time. (The study also covers residents' perceptions of the built environment - the whole thing is worth a read for anyone interested in this topic.)

The authors found that "there is a significant association between LRT use and reductions in BMI over time." The details are as follows:

Specifically, LRT reduced their BMI by an average of 1.18 kg/m2 compared to similarly situated non-LRT users over a 12-18 month follow-up period. For a person who is 5â²5â³, that is equivalent to a relative weight loss of 6.45 lbs. Use of LRT is also associated with a reduced odds of becoming obese (OR=0.19, 95% CI=0.04, 0.92). LRT users were 81% less likely to become obese over time. The odds of increasing one's physical activity through vigorous exercise to meet RPA levels is also associated with LRT use (OR=3.32, 95% CI=0.81, 3.63) but was only significant at the p

There are many reasons to shift more of our transportation from single-occupancy vehicles to public transportation, including reducing pollution and congestion and improving quality of life for those who can't drive (whether due to age, physical limitations, or inability to afford a car). If such a shift can also play a role in reducing obesity, that makes the case for transit even stronger. I hope in the coming years we'll see more new transit lines added, and more researchers taking the opportunity of these natural experiments to study how public transportation affects public health.

Citation: MacDonald JM, Stokes RJ, Cohen DA, Kofner A, Ridgeway GK. The Effect of Light Rail Transit on Body Mass Index and Physical Activity. Am J Prev Med 2010; 39(2):105-112. doi: 10.1016/j.amepre.2010.03.016.

lborkowski Wed, 09/01/2010 - 13:26