Using GPS and Accelerometers to Study Neighborhood Walkability and Physical Activity

We just published a paper in the American Journal of Preventive Medicine showing that differences in residential neighborhood walkability in New York City (NYC) are associated with how residents utilize neighborhood space and are associated with total weekly physical activity. Higher neighborhood walkability was associated with significantly more physical activity and differences in activity attributable to variation in urban design were substantial when compared to the recommended goal of achieving 150 minutes  of moderate intensity physical activity per week.

Examples of high and low walkability neighborhoods and a map of Neighborhood Walkability Index scores for all of NYC

Examples of high and low walkability neighborhoods and a map of neighborhood walkability for all of NYC

The research was conducted in collaboration with researchers from the NYC Department of Health and Mental Hygiene and analyzed Global Positioning System (GPS) and physical activity data from the Physical Activity and Transit Survey (PAT).  For a period of a week, PAT study participants wore an accelerometer to continuously measure physical activity and a GPS logger that recorded the participant’s location multiple times per minute.  In all, the PAT Survey collected over 8 million GPS location readings, known as waypoints, as the study participants (n=803) went about their daily lives.

Four illustrative examples of minimally convex polygons (white area) around GPS waypoints falling within 1Km of the residence (total area of circles).

Four illustrative examples showing how GPS logging data can be used to characterize which parts, and how much, of someone’s residential neighborhood is actually utilized by the person. The circle represents all neighborhood space within 1Km of a residence and the white area reflects a minimal convex polygon that encompasses GPS waypoints. They grey area represents space within 1Km of the residence that was not utilized.

To identify how much area within their residential neighborhood participants utilized during the monitoring period, we defined a minimally convex polygon around GPS waypoints falling within 1Km of each participant’s home.  This 1Km circular area around the home has commonly been used in prior research to define study participant’s residential neighborhoods.  The use of convex polygons around GPS waypoints to define the utilized residential area is similar to methods used in wildlife studies to define the home territory of animals. In NYC we see that residents vary considerably in how much of the total 1Km circular residential neighborhood area they actually use as judged by the area encompassed by the GPS data. Continue reading

Posted in Accelerometers, GPS, Physical Activity, Walkability | Leave a comment

The CDC and DoT’s Transportation and Health Tool

Viewing 125th Street

Viewing 125th Street

The Centers for Disease Control and Prevention and Department of Transportation just released the new Transportation and Health Tool, which provides easy access to data that examines the health impacts of transportation systems. The Transportation and Health Tool provides data on 14 transportation and public health indicators for each state, metropolitan statistical area (MSA), and urbanized area (UZA). The indicators measure how the transportation environment affects health with respect to safety, active transportation, air quality, and connectivity to destinations.  You can use the tool to quickly see how a state, MSA, or UZA compares with others in addressing key transportation and health issues. The tool also provides information and resources to help agencies better understand the links between transportation and health and to identify strategies to improve public health through transportation planning and policy

Posted in Active Transport, Transportation | Leave a comment

Tree Canopy Data for the Entire State of Pennsylvania

Jarlath O’Neil-Dunne at the University of Vermont just announced the release of a statewide, high-resolution tree canopy dataset for Pennsylvania.  The resolution of the data is 1 m which makes it 900 times more detailed than the National Land Cover Dataset; this is an amazing feat.

We previously worked with Jarlath to create tree canopy data for NYC and looked at the link between tree canopy coverage and asthma and allergic sensitization among children in NYC.


Tree canopy coverage in Washington Heights, NYC

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Strategies to Refine Annual Business Establishment Data across More than Two Decades

Analyses of place and health have been largely cross-sectional, and new challenges are faced as we wrangle longitudinal geographic data.  Our group just published a manuscript detailing our work to clean and code data on all NYC metropolitan area businesses over the period 1990-2010.  Our goal was to use twenty years of business establishment data to characterize changes in neighborhoods in terms of the retail food environment, access to physical activity venues, access to medical facilities and access to other commercial and not-for-profit establishments.

Our process included re-geocoding 3,161,715 business locations to avoid disproportionately missing data on older businesses; identifying and coding health-relevant businesses such as food sources and fitness venues across the years; and collapsing potential duplicate business records by location, year, and business category.  Spot-checking was used, and the data are set up to allow for sensitivity analyses to check the robustness to these decisions as we move forward.

This effort was championed by lead author Tanya Kaufman, who has engaged in this effort since her MPH practicum project using these data.  Daniel Sheehan was the lead geographer on the project and developed the re-geocoding strategies and created time-lapse visualizations of businesses entering and existing the environment. One of Dan’s visualizations can be seen here.  It shows the location of Healthy Food Outlets from 1990 to 2010.

The focus of this project was not only to understand and improve the quality of data for future analysis, but also to develop scalable approaches that can be used with the larger national dataset.  We have recently been funded to purchase the nationwide business establishment data and to link these data to ongoing cohort studies of cardiovascular disease  (R01AG049970-01A1, PI: Lovasi).


Posted in Economic Development, Food Environment, Methods | Leave a comment

CDC Releases New Built Environment Assessment Tool

Viewing 125th Street

Viewing 125th Street

The CDC released a new direct systematic observation data collection instrument for measuring the core features and quality of the built environment related to behaviors that affect health, especially behaviors such as walking, biking, and other types of physical activity.  The core features assessed in the BE Tool include: built environment infrastructure (e.g., road type, curb cuts/ramps, intersections/crosswalks, traffic control, transportation), walkability (e.g. sidewalk/path features, walking safety, aesthetics & amenities), bikeability (e.g., bicycle lane/path features), recreational sites and structures, and the food environment (e.g., access to grocery stores, convenience stores, farmers markets, etc.).

Get the tool [HERE]


Posted in Community Needs Assessment, Methods, Walkability | Leave a comment

Systematic Review of Literature on Neighborhood Park Access and Physical Activity

Trail map for Fort Tryon Park - more difficult trails

Trail map for Fort Tryon Park

Providing neighborhood access to clean, safe and engaging park spaces is a strategy being adopted by many communities to promote physical activity.  We just published a systematic review of the literature assessing the link between park access and physical activity. After screening 10,949 abstracts that met the search criteria of 1) published between January 1990 and June 2013; 2) US-based with a sample size greater than 100 individuals; 3) included built environment measures related to parks or trails; and 4) included objectively measured physical activity as an outcome, 20 research studies were identified for review.

Five articles reported a significant positive association between parks and physical activity. Nine studies found no association, and six studies had mixed findings.  Studies that used study subject’s self-reported (vs. independently-measured) measures of neighborhood park environment characteristics and smaller (vs. larger) neighborhood definitions were more likely to find positive associations. We recommend strategies for further research, employing standardized reporting and innovative study designs to better understand the relationship of parks and physical activity.


Posted in Parks, Systematic Review | Leave a comment

Mailman School’s Social Epidemiology Cluster launches a Blog


The Social Epidemiology Cluster is one of the six thematic units within the Mailman School of Public Health‘s Department of Epidemiology and is home to BEH members Andrew Rundle and Gina Lovasi.  The Cluster has just launched a blog that will highlight the importance of research and interventions focused on social determinants of health for promoting population health and reducing disparities.  The blog will include commentary on research news and policy debates and initiatives, and will disseminate research findings from work being performed at Columbia University.

Posted in Social Determinants | Leave a comment

Neighborhood Safety and Physical Activity

Would you go for a walk around the block or in a local park if you thought your neighborhood unsafe and you would be in danger? At BEH, we care a lot about understanding constraints on outdoor physical activity, including (maybe) safety.

The link between neighborhood safety and physical activity has been tricky to assess, in part because physical activity is tricky to measure (questionnaires are vulnerable to reporting biases and don’t capture small-scale differences in activity between people whereas accelerometers and other activity trackers are sensitive to proper positioning), and in part because no single construct completely represents neighborhood safety – some researchers study fear of victimization, others study crime rates, and still others study aesthetic features such as disorder that may affect the perception that a neighborhood is unsafe.


Download the PAA Poster

We recently investigated several measures of safety, including self-reported neighborhood safety, crime rates, and a measure of neighborhood disorder we constructed using Street View imagery in relation to accelerometer-measured and self-reported physical activity, using data from the Physical Activity and Transit survey undertaken by the New York City Department of Health and Mental Hygiene. We found that independently observed measures of neighborhood safety and disorder were not associated with any measures of physical activity, but that reporting the neighborhood to be unsafe was associated with increased odds of reporting no recreational physical activity.

The initial results of our work were presented as a poster at the recent annual meeting of the Population Association of America.

Posted in Aesthetics, Physical Disorder, Safety | Leave a comment

Spatial Patterns of Exposure to Tree Pollen in Cities

Betula sp. pollen [Birch Pollen] photo by Guy Robinson, Fordam University

Betula sp. pollen [Birch Pollen] photo by Guy Robinson, Fordam University

BEH investigator Gina Lovasi has recently worked with colleagues from Environmental Health Sciences (EHS) on a systematic review of how tree pollen levels vary spatially within cities (available at  This review is part of our larger effort to inform refinement and evaluation of massive urban tree planting efforts currently underway in cities such as NYC and Los Angeles.

Seasonal allergies to tree pollen and other outdoor allergens (grasses, ragweed, mold) trigger respiratory symptoms and asthma exacerbations in urban populations.  Tree pollen in particular tends to affect people early in mid-spring.  While current pollen levels can readily be compared across broad areas of the US (for example see, less is known about small scale variation of exposure within a city.  Single rooftop monitors tracking daily pollen counts are often used to represent the experience of the entire city.  Yet multiple monitoring points would be needed to help us understand how much exposure to tree pollen is driven by a city’s overall tree canopy and regional context versus vegetation in the immediate vicinity. Continue reading

Posted in Urban Forestry | Leave a comment

A SMART START: A Symposium on Preventing Childhood Obesity

On April 16th the Mailman School is presenting an afternoon long symposium, “A SMART START:  A Symposium on Preventing Childhood Obesity“, focused on prenatal and early childhood determinants of obesity.  This symposium is part of a month long series of events in April we are calling “Public Health Fights Obesity”.   You can RSVP to attend the symposium by clicking HERE


1:00–5:00 P.M.

A Symposium on Preventing Childhood Obesity

Black Building, 650 West 168th Street
Alumni Auditorium

PLENARY: Why Focus on Pregnancy and Early Childhood?

Andrew Rundle, DrPH, Associate Professor of Epidemiology; Co-Director of Obesity Prevention Initiative, Columbia Mailman School of Public Health

PANEL 1: Gestational Weight Change, Prenatal Factors and Childhood Obesity

Moderator: Virginia Rauh, ScD, Professor of Population and Family Health, Columbia Mailman School of Public Health


Dympna Gallagher, EdD, Associate Professor of Nutritional Medicine, Institute of Human Nutrition, Columbia University College of Physicians & Surgeons

David A Savitz, PhD, Vice President for Research, Professor of Epidemiology, Professor of Obstetrics and Gynecology, Brown University

Cynthia Gyamfi-Bannerman, MD, Associate Professor of Maternal-Fetal Medicine, Director of Maternal-Fetal Medicine Fellowship Program, Medical Director of Perinatal High-Risk Clinic, Columbia University Medical Center

PANEL 2: Early Childhood Factors and Early Childcare Practice and Policies

Moderator: Gretchen Van Wye, PhD, MA, Assistant Commissioner, Bureau of Vital Statistics, NYC Department of Health and Mental Hygiene, Division of Epidemiology


Cynthia Colen, PhD, MPH, Assistant Professor of Sociology, The Ohio State University

Cathy Nonas, MS, RD, Senior Advisor, NYC Department of Health and Mental Hygiene

Sally E Findley, PhD, Professor of Population and Family Health & Sociomedical Sciences, Columbia Mailman School of Public Health

Round Table: Future Directions for Research and Action

Moderator: Y. Claire Wang, MD, ScD, Associate Professor of Health Policy and Management and Co-Director of Obesity Prevention Initiative, Columbia Mailman School of Public Health


Kiyah Duffey, PhD, Director of Global Scientific Affairs, LA Sutherland Group; Parenting blogger and proud mother of three, ages 5 and under

Tina Kauh, PhD, Program Officer, Research-Evaluation-Learning, Robert Wood Johnson Foundation

Posted in Childhood | Leave a comment