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“HF/E Professionals: Help Make Biking to School Safer” (2010)

• This article outlines how human factors and ergonomics professionals and parents can make a difference in their community by supporting a return to safe active school transportation.
• The associated risks have been identified through research, and the effectiveness of various safety interventions has been assessed, providing many opportunities to contribute toward a safer cycling environment in which more children may enjoy the benefits of active school transportation. This article focuses on bicycling, but much of the discussion applies to walking as well. 

Ayres, T. J. (2010). HF/E Professionals: Help Make Biking to School Safer. Ergonomics in Design 18(3), 30-31.

“Infrastructure, Programs, and Policies to Increase Bicycling: An International Review” (2010)

• To assess existing research on the effects of various interventions on levels of bicycling. Interventions include infrastructure (e.g., bike lanes and parking), integration with public transport, education and marketing programs, bicycle access programs, and legal issues.
• A comprehensive search of peer-reviewed and non-reviewed research identified 139 studies. Study methodologies varied considerably in type and quality, with few meeting rigorous standards. Secondary data were gathered for 14 case study cities that adopted multiple interventions.
• Many studies show positive associations between specific interventions and levels of bicycling. The 14 case studies show that almost all cities adopting comprehensive packages of interventions experienced large increases in the number of bicycle trips and share of people bicycling.
• Most of the evidence examined in this review supports the crucial role of public policy in encouraging bicycling. Substantial increases in bicycling require an integrated package of many different, complementary interventions, including infrastructure provision and pro-bicycle programs, supportive land use planning, and restrictions on car use.

Pucher, Dill, and Handy, “Infrastructure, Programs, and Policies to Increase Bicycling,” Preventive Medicine, Jan 2010, Vol. 50, S.1, pp. S106-S125.

“Facility Provision in Elementary Schools: Correlates with Physical Education, Recess, and Obesity” (2010)

• The objectives were to: (1) document correlations among facility provision (availability and adequacy) in elementary schools, child sociodemographic factors, and school characteristics nationwide; and (2) investigate whether facility provision is associated with physical education (PE) time, recess time, and obesity trajectory.
• The analytic sample included 8935 fifth graders from the Early Childhood Longitudinal Survey Kindergarten Cohort. School teachers and administrators were surveyed about facility provision, PE, and recess time in April 2004. Multivariate linear and logistic regressions that accounted for the nesting of children within schools were used.
• Children from disadvantaged backgrounds were more likely to attend a school with worse gymnasium and playground provision. Gymnasium availability was associated with an additional 8.3 min overall and at least an additional 25 min of PE per week for schools in humid climate zones. These figures represent 10.8 and 32.5%, respectively, of the average time spent in PE. No significant findings were obtained for gymnasium and playground adequacy in relation to PE and recess time, and facility provision in relation to obesity trajectory.
• Poor facility provision is a potential barrier for school physical activity programs and facility provision is lower in schools that most need them: urban, high minority, and high enrollment schools.

Fernandes M, Sturm R. “Facility provision in elementary schools: Correlates with physical education, recess, and obesity.” Preventive Medicine 2010; 50(S1): S30-S35.

“Aerobic Fitness and Mode of Travel to School in English School Children” (2010)

• Cycling to school is positively associated with aerobic fitness in Danish schoolchildren and adolescents. The aim of the present study was to determine whether a positive association exists between active travel and aerobic fitness in English schoolchildren, where cycling to school is rare.
• Participants (n = 6085, 47% girls, aged 10.0-15.9 yr) were recruited as part of the East of England Healthy Hearts study. Mass and stature were measured, and body mass index (BMI) was calculated. Aerobic fitness was assessed using the 20-m shuttle run test (20-mSRT); mode of travel to school and physical activity (PA) were assessed by a questionnaire. Differences in BMI, PA, and fitness by travel mode were assessed by ANOVA and ANCOVA. Participants were categorized as "fit" or "unfit" on the basis of existing cutoffs related to adult health. Logistic regression was applied to calculate age, BMI, and PA-adjusted odds of being classified as fit according to travel mode.
• Walking was the most common travel mode to school (50%), and cycling was least frequent (8%). Walkers and cyclists of both sexes were significantly fitter than passive transport users, even after controlling for PA. Walking and cycling were associated with an increased likelihood of being categorized as fit in boys and girls. After adjustment for PA, this association remained significant only in girls. No association was observed between travel mode and BMI.
• These data confirm findings from countries where cycling is very common in showing that cycling to school is positively associated with aerobic fitness. This study adds to the existing literature by showing that walkers and cyclists are more likely to be classified as fit using recognized cut points. Those who walk and cycle to school may, therefore, be at reduced risk for developing chronic diseases in adulthood.

Voss C and Sandercock G. “Aerobic Fitness and Mode of Travel to School in English School Children.” Medicine & Science in Sports & Exercise 2010; 281-287.

“Interventions to promote cycling: systematic review” (2010)

• The purpose of this study is to determine what interventions are effective in promoting cycling, the size of the effects of interventions, and evidence of any associated benefits on overall physical activity or anthropometric measures via a systematic review of the published and unpublished reports.
• The review consisted of controlled “before and after” experimental or observational studies of the effect of any type of intervention on cycling behavior measured at either individual or population level.
• Twenty five studies (of which two were randomized controlled trials) from seven countries were included. Six studies examined interventions aimed specifically at promoting cycling, of which four (an intensive individual intervention in obese women, high quality improvements to a cycle route network, and two multifaceted cycle promotion initiatives at town or city level) were found to be associated with increases in cycling. Those studies that evaluated interventions at population level reported net increases of up to 3.4 percentage points in the population prevalence of cycling or the proportion of trips made by bicycle. Sixteen studies assessing individualized marketing of “environmentally friendly” modes of transport to interested households reported modest but consistent net effects equating to an average of eight additional cycling trips per person per year in the local population. Other interventions that targeted travel behavior in general were not associated with a clear increase in cycling. Only two studies assessed effects of interventions on physical activity; one reported a positive shift in the population distribution of overall physical activity during the intervention.
• Community-wide promotional activities and improving infrastructure for cycling have the potential to increase cycling by modest amounts, but further controlled evaluative studies incorporating more precise measures are required, particularly in areas without an established cycling culture. Studies of individualized marketing report consistent positive effects of interventions on cycling behavior, but these findings should be confirmed using more robust study designs.
• Future research should also examine how best to promote cycling in children and adolescents and through workplaces. Whether interventions to promote cycling result in an increase in overall physical activity or changes in anthropometric measures is unclear.

Yang, L., S. Sahlqvist, et al. (2010). "Interventions to Promote Cycling: Systematic Review." BMJ 341.

“Neighborhood design and perceptions: relationship with active commuting” (2010)

• Walking to and from school contributes to total physical activity levels. This study investigated whether perceived and actual neighborhood features were associated with walking to or from school among adolescent girls.
• A sample of 890 geographically diverse eighth-grade girls completed a self-administered survey on their neighborhood features and walking behavior. GIS data were used to assess objective neighborhood features.
• The study found that:
• Safety, land use, and school location issues need to be considered together when designing interventions to increase walking to and from school.

Voorhees, CC, Ashwood, S, Evenson, KR, Sirard, JR, Rung, AL, Dowda, M, Mckenzie, TL. “Neighborhood design and perceptions: relationship with active commuting.” Journal of Medicine and Science in Sports And Exercise. 42.7 (2010): 1253-1260.

Pedometer-Measured Physical Activity and Health Behaviors in U.S. Adults (2010)

• The purpose of this study is to provide descriptive, epidemiological data on the average number of steps per day estimated to be taken by U.S. adults and to identify predictors of pedometer-measured physical activity on the basis of demographic characteristics and self-reported behavioral characteristics.
• Individuals aged 13 yr and older consented to fill out a survey, including 1921 adults aged 18 yr and older. Valid pedometer data were collected on 1136 adults with Accusplit AE120 pedometers.
• Adults reported taking an average of 5117 steps per day.
• Male gender, younger age, higher education level, single marital status, and lower body mass index were all positively associated with steps per day. Steps per day were positively related to other self-reported measures of physical activity and negatively related to self-reported measures on physical inactivity. Living environment (urban, suburban, or rural) and eating habits were not associated with steps per day.
• In the current study, men and women living in the United States took fewer steps per day than those living in Switzerland, Australia, and Japan. We conclude that low levels of ambulatory physical activity are contributing to the high prevalence of adult obesity in the United States.

Bassett, David R., Wyatt, Holly R., Thompson, Helen, Peters, John C., and Hill, James O. “Pedometer-Measured Physical Activity and Health Behaviors in U.S. Adults.” Medicine & Science in Sports & Exercise. 42.10 (2010): 1819-1825.

The Medical Care Costs of Obesity: An Instrumental Variables Approach (2010)

• This paper by the National Bureau of Economic Research is the first to estimate the impact of obesity on medical costs in order to address the endogeneity of weight and to reduce the bias from reporting error in weight.
• The report shows that nearly 17 percent of medical costs in the United States, or $168 billion, can be attributed to obesity. This is nearly twice the amount previously estimated.
• The study also concluded that obesity adds more than $2,800 to an individual’s annual medical costs.
• The results imply that the previous literature has underestimated the medical costs of obesity, resulting in underestimates of the cost effectiveness of anti-obesity interventions and the economic rationale for government intervention to reduce obesity-related externalities.

Cawley, John and Meyerhoefer, Chad. “The Medical Care Costs of Obesity: An Instrumental Variables Approach.” National Bureau of Economic Research. Working Paper No. 16467 (2010).

Active living for rural children: community perspectives using PhotoVOICE (2010)

• The purpose of this study is to identify the perceived environmental factors that support or hinder physical activity among rural children to develop testable hypotheses to inform future interventions for reducing unhealthy weight gain and preventing chronic diseases associated with physical inactivity.
• PhotoVOICE was used to explore active living opportunities and barriers for children living in four low-income, rural U.S. communities. In 2007, parents and elementary school staff received disposable cameras to document their perspective. Using their photographs and narratives, participants developed emergent themes during a facilitated group discussion. Study authors used the Analysis Grid for Environments Linked to Obesity (ANGELO) framework to categorize the themes.
• Microenvironment themes include physical (e.g., natural features, topography); sociocultural (e.g., isolation); policy (e.g., time for school recess); and economic (e.g., funding for physical activity programs). Macroenvironmental themes related to the built and natural environments and transportation infrastructure.
• This study identified rural environment elements that community members perceived as influencing children’s physical activity patterns. Certain aspects were unique to rural areas, whereas other urban and suburban factors may be generalizable to rural settings.

Hennessy, E., Kraak, VI., Hyatt, RR., Bloom, J., Fenton, M., Wagoner, C., and Economos, CD. “Active Living for Rural Children: Community Perspectives Using PhotoVoice.” American Journal of Preventive Medicine. 39.6 (2010): 537-545.

Ethnic Minority Children’s Active Commuting to School and Association with Physical Activity and Pedestrian Safety Behaviors (2010)

• Researchers conducted a cross-sectional analysis of baseline measurements from a sample of participants aged 9-12 years from a walk to school intervention study in Houston, Texas. The primary outcome was the weekly rate of active commuting to school. Daily moderate-to-vigorous physical activity, measured by accelerometers, was a secondary outcome.
• Among the sample, which was 61.7% Latino, the overall rate of active commuting to school was 43%. Latino students had lower rates of active commuting to school than non-Latinos (16.5%). Distance from home to school was inversely related to active commuting to school.
• Among the Latino subsample, child acculturation was negatively associated with active commuting to school.
• With regard to school-level pedestrian safety observations, 37% of students stopped at the curb and 2.6% looked left-right-left before crossing the street.
• Although still below national goals, the rate of active commuting was relatively high, while the rate of some pedestrian safety behaviors was low among this low-income, ethnic minority population. Programs and policies to encourage safe active commuting to school are warranted and should consider the influence of parents, acculturation, and ethnicity.

Mendoza, Jason A., Watson, Kathy, Baranowski, Tom, Nicklas, Theresa A., Uscanga, Doris K., Nguyen, Nga, and Hanfling, Marcus J. "Ethnic Minority Children’s Active Commuting to School and Association with Physical Activity and Pedestrian Safety Behaviors." Journal of Applied Research on Children: Informing Policy for Children at Risk. 1.1.4 (2010).

A Pilot Walking School Bus Program to Prevent Obesity in Hispanic Elementary School Children: Role of Physician Involvement with the School Community (2010)

• The University of New Mexico School-Based Health Center (UNM SBHC) collaborated with the school and community to test the feasibility of a modified Walking School Bus (WSB) program as a strategy to prevent obesity among the elementary school students.
• Kindergarten through fifth-grade students were recruited through classroom presentations by an SBHC physician to 2 WSBs that ran sequentially from March to May 2006 for 10 weeks. Students residing within 1 mile of the school were eligible.
• Participants walked on designated routes with pick-up and drop-off locations approved for safety by the police department.
• Four health themes were emphasized during the walks by a premedical student fluent in Spanish and 2 medical students, one of whom was fluent in Spanish: (a) get up and play, (b) turn off your television, (c) eat 5 servings of fruit/vegetables per day, and (d) reduce soda/juice intake.
• Seventy-six percent of students enrolled walked an average of 3 or more times per week. BMI percentile remained stable among participants both overweight and not overweight. Physical activity increased from a mean of 4.3 days/week to 5.3 days/week (P = .08), and fruit serving consumption nearly doubled (P = .01) according to pre/post surveys (Table 1). Vegetable intake more than doubled by 24-hour diet recalls (P < .001). There were no significant changes in television viewing time and soda/juice intake.
• The WSB appeared quite suitable to one of the poorest areas of town, with only 3 students dropping out.
• Pilot WSB findings of BMI percentile maintenance in growing students coupled with obesity reduction behavior changes are encouraging.

Kong, Alberta S., Burks, Nichole, Conklin, Cristina, Roldan, Carlos, Skipper, Betty, Scott, Susan, Sussman, Andrew L., and Leggott, John. “A Pilot Walking School Bus Program to Prevent Obesity in Hispanic Elementary School Children: Role of Physician Involvement with the School Community.” Clinical Pediatrics. 49.10 (2010): 989-991.

“Neighborhood, route, and school environments and children’s active commuting” (2010)

• This study aims to assess whether objectively measured characteristics of the neighborhood, route, and school environments are associated with active commuting to school among children, and it explores whether distance acts as a moderator in this association.
• A cross-sectional study was conducted of 2012 children (899 boys and 1113 girls) aged 9-10 years attending 92 schools in the county of Norfolk, United Kingdom.
• Children who lived in a more deprived area and whose route to school was direct were less likely to walk or cycle to school, whereas those who had a higher density of roads in their neighborhood were more likely to walk.
• Children whose routes had a high density of streetlights were less likely to cycle to school.
• Objectively measured neighborhood and route factors are associated with walking and cycling to school.
• Distance did not moderate the associations found in this study.
• Creating safe environments by improving urban design may influence children’s commuting behavior.

Panter JR, Jones AP, Van Sluijs EM, and Griffin SJ. “Neighborhood, Route, and School Environments and Children’s Active Commuting.” American Journal of Preventive Medicine. 38.3 (2010): 268-78.

“Validity of Instruments to Assess Students’ Travel and Pedestrian Behaviors” (2010)

• This study validated the SRTS school travel survey and a pedestrian safety behavior checklist
  • The school travel survey is a written survey completed by both parents and students to measure how students traveled to school on that given day.
  • The pedestrian safety behavior checklist assesses if a pedestrian is following safety elements including: crossed at a corner or crosswalk, crossed with an adult or safety patrol, stopped at the curb, looked left-right-left, kept looking while crossing, walked and did not run across the street, and followed the traffic signal (if present).
• The validation of these instruments has significant implications on the ability to assess SRTS programs.

Mendoza, Jason A., Watson, Kathy, Baranowski, Tom, Nicklas, Theresa A., Uscanga, Doris K., and Hanfling, Marcus J. “Validity of Instruments to Assess Students’ Travel and Pedestrian Safety.” BMC Public Health. 10.257 (2010).

“The Association Between Community Physical Activity Settings and Youth Physical Activity, Obesity and Body Mass Index” (2010)

• This study examines the association between the level of physical activity (PA), friendliness of the built environment and adolescent physical activity and body mass index using a national sample of youth and data collected from the communities where they reside.
• Increased levels of area deprivation were associated with decreased physical activity and higher weight.
• A greater number of commercial physical activity facilities was associated with increased physical activity.
• More compact communities were associated with lower weight and less sports participation.
• Researchers suggest that it is important to explore these associations to help guide future development patterns and land use policies to create more active neighborhoods.

Slater, Sandy J., Ewing, Reid, Powell, Lisa M., Chaloupka, Frank J., Johnston, Lloyd D., and O’Malley, Patrick M. “The Association Between Community Physical Activity Settings and Youth Physical Activity, Obesity, and Body Mass Index. Journal of Adolescent Health. (2010): 1-8.

“A Qualitative GIS Approach to Mapping Urban Neighborhoods with Children to Promote Physical Activity and Child-Friendly Community Planning” (2010)

• In this study, researchers stress the importance in considering the role of neighborhoods in supporting children’s physical activity and healthy development, especially in low-income communities where obesity levels among children are higher than for their middle-income counterparts.
• This study is a participatory and qualitative GIS approach to mapping children’s own perceptions and use of their neighborhood for physical activity among ten and eleven year-olds growing up in a diverse low-income community in Denver, CO.
• Girls walk shorter distances to and use different types of community spaces for play and recreation from boys, some of which is explained by the differing environmental-socialization approaches employed by parents and caregivers.
• Children’s perceptions of risk align spatially with features of the built environment, but do not correlate with reported crime.
• Results illustrate the utility of qualitative spatial analysis to understand relationships between children’s perception, the built environment, and social factors that shape children’s active transport, leisure, and recreation in their neighborhood.
• Children’s local knowledge should be valued and solicited in community-level health and planning interventions to promote physical activity.

Wridt, Pamela. “A Qualitative GIS Approach to Mapping Urban Neighborhoods with Children to Promote Physical Activity and Child-Friendly Community Planning.” Environment and Planning B: Planning and Design. 37.2 (2010): 129-147.

“School Siting: Contested Visions of the Community School” (2010)

• In this study, McDonald traces the evolution of school siting standards, explains the factors currently influencing school facility location decisions, and identifies what local and regional planners could contribute to school siting decisions.
• Smart growth proponents advocate community schools that are small and intimately linked to neighborhoods
• School facility planners tent to expect community schools to meet the needs of entire localities.
• McDonald recommends communities consider tradeoffs associated with different schools sizes including:
  • Walking distance for students
  • Potential for sports fields
  • School design
  • Connections to neighborhoods
• McDonald also recommends that state school construction and siting policies support flexibility for localities and that local and regional planners should work with school facility planners to conduct exercises and charettes to help each community determine how to realize its own vision of community schools.

McDonald, Noreen. “School Siting: Contested Visions of the Community School.” Journal of the American Planning Association. 76.2 (2010).

“The Association Between School-Based Physical Activity, Including Physical Education, and Academic Performance” (2010)

• Student physical activity may help improve academic performance including academic achievement (e.g., grades, standardized test scores); academic behavior (e.g., on-task behavior, attendance); and factors that can positively influence academic achievement (e.g. concentration, attention, improved classroom behavior).
• This report is a literature review that examines the existing research on the relationship between school-based physical activity, including physical education, and academic performance. It spans 23 years of research and includes 50 studies.
• The majority of the studies in this review report that physical activity was positively related to academic performance.
• Adding time during the school day for physical activity does not appear to take away from academic performance.
• Schools should continue to offer and/or increase opportunities for student physical activity.

Centers for Disease Control and Prevention. The Association between School-based Physical Activity, Including Physical Education, and Academic Performance. Atlanta, GA: U.S. Department of Health and Human Services; 2010.

“Aerobic Fitness and Mode of Travel to School in English Schoolchildren” (2010)

• This purpose of this study was to determine whether a positive association exists between active travel and aerobic fitness in English schoolchildren.
• Researchers collected data on mass and structure, BMI, and aerobic fitness (through 20-m shuttle run) on participants, school children ages 10-15.9 years old.
• Mode of travel to school and physical activity was assessed by a questionnaire.
• Results indicate that walking was the most common travel mode to school (50%), and cycling was the least frequent (8%).
• Walkers and cyclists were significantly fitter than passive transport users.
• No association was observed between travel mode and BMI
• Researchers suggest that this study supports existing literature that suggests that those who walk and cycle to school may be at a reduced risk for developing chronic diseases in adulthood.

Voss, Christine and Sandercock, Gavin. “Aerobic Fitness and Mode of Travel to School in English Schoolchildren.” Medicine and Science in Sports and Exercise. 42.2 (2010): 281-287.

“State School Nutrition and Physical Activity Policy Environments and Youth Obesity” (2010)

• Using 2006 School Health Policies and Programs Study (SHPPS) state data, this study develops a comprehensive approach to characterize the overall prevention policy environment for schools and links the policy environments to youth obesity for each state.
• Of nearly 250 state-level obesity prevention-policy questions, the analysis and assessment suggested the reality of the number of policies adopted by states:
  • On average states adopted about half (49%) of the 100 food service and nutrition policies
  • 38% of the 146 physical activity and education policies
  • 17% of the weight assessment policies
• After adjusting for ethnicity and income, the average proportion of food service and nutrition policies adopted by states was correlated with the prevalence of youth obesity.
• No correlation was found between physical activity and education or weight assessment policies and youth obesity.

Nanney, Marilyn S., Nelson, Toben, Wall, Melanie, Haddad, Tarek, Kubik, Martha, Laska, Melissa Nelson, and Story, Mary. “State School Nutrition and Physical Activity Policy Environments and Youth Obesity.” American Journal of Preventive Medicine. 38.1 (2010): 9-16.

“Influence of the Social Environment on Children’s School Travel” (2010)

• This study analyzes the association between parental perceptions of the social environment and walking and biking to school among 10-14 year-olds.
• The social environment was measured with a 3-item scale assessing child-centered social control.
• Of children whose parents reported high levels of social control, 37% walked or biked to school, compared with 24% of children whose parents reported low or neutral levels.
• The association was strongest for girls and non-Hispanic whites.
• Researchers conclude that higher levels of parent-perceived child-centered social control are associated with more walking and biking to school. Therefore, increasing physical activity through active travel to school may require intervention programs to address the social environment.

McDonald, N., Deakin, E., and Aalborg, A.E. “Influence of the Social Environment on Children’s School Travel.” Preventive Medicine. 50.Suppl 1 (2010): 65-68.

“Mapping the Walk to School Using Accelerometry Combined with a Global Positioning System” (2010)

• This study combined accelerometer and GPS data to investigate the level and location of physical activity in children walking to school.
• Mean accelerometer counts per minute before school were 43% higher in children who walked to school than those traveling by car.
• 11% of daily moderate to vigorous physical activity occurred during the walk to school.
• Total activity during the walk to school was twice that in the playground, with the journey to school contributing three times as much moderate to vigorous physical activity as time in the playground.

Cooper, Ashley R., Page, Angie S., Wheeler, Benedict W., Griew, Pippa, Davis, Laura, Hillsdon, Melvyn, and Jago, Russell. American Journal of Preventive Medicine. 38.2 (2010): 178-183.

“Vehicle Emissions during Children’s School Commuting: Impacts of Education Policy” (2010)

• This study explores how school policies influence the environmental impacts of school commutes, motivated by increased interest in school choice policies and in reducing bus services to address recent budget shortfalls.
• Results indicate that eliminating district-wide school choice (i.e., returning to a system with neighborhood schools only) would have significant impacts on transport modes and emissions, whereas in many cases proposed shifts in school choice and bus-provision policies would have only modest impacts.
• Policies such as school choice and school siting may conflict with the goal of increasing rates of active (i.e., nonmotorized) school commuting.
• Researchers report that these findings underscore the need to critically evaluate transportation-related environmental and health impacts of currently proposed changes in school policy.

Marshall, JD, Wilson, RD, Meyer, KL, Rajangam, SK, McDonald, NC, and Wilson, EJ. “Vehicle Emissions during Children’s School Commuting: Impacts of Education Policy.” Environmental Science and Technology. (2010)

“Infrastructure programs and policies to increase bicycling: An international review” (2010)

• This review assesses existing research on the effects of various interventions on levels of bicycling including infrastructure, integration with public transport, education and marketing program, bicycle access programs and legal issues.
• A review of 139 studies shows positive associations between specific interventions and levels of bicycling.
• A secondary review of 14 case studies of cities adopting multiple interventions show that almost all cities adopting comprehensive packages of interventions experienced large increases in the number of bicycle trips and share of people bicycling.
• Substantial increases in bicycling require an integrated package of many different, complementary interventions, including infrastructure provision and pro-bicycle programs, supportive land use planning, and restrictions on car use.

Pucher, John, Dill, Jennifer, and Handy, Susan. “Infrastructure programs and policies to increase bicycling: An international review.” American Journal of Preventive Medicine. 50 (2010): S106-S125.

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