Archives 3 - Impact of Physical Activity
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- Although from a societal point of view a modal shift from car to bicycle may have beneficial health effects due to decreased air pollution emissions, decreased greenhouse gas emissions, and increased levels of physical activity, shifts in individual adverse health effects such as higher exposure to air pollution and risk of a traffic accident may prevail.
- This study describes whether the health benefits from the increased physical activity of a modal shift for urban commutes outweigh the health risks.
- This paper provides a summary of the literature for air pollution, traffic accidents, and physical activity using systematic reviews supplemented with recent key studies.
- The authors quantified the impact on all-cause mortality when 500,000 people would make a transition from car to bicycle for short trips on a daily basis in the Netherlands. They expressed mortality impacts in life-years gained or lost, using life table calculations. For individuals who shift from car to bicycle, they estimated that beneficial effects of increased physical activity are substantially larger (3–14 months gained) than the potential mortality effect of increased inhaled air pollution doses (0.8–40 days lost) and the increase in traffic accidents (5–9 days lost). Societal benefits are even larger because of a modest reduction in air pollution and greenhouse gas emissions and traffic accidents.
- On average, the estimated health benefits of cycling were substantially larger than the risks relative to car driving for individuals shifting their mode of transport.
de Hartog, J. J., H. Boogaard, et al. (2010). "Do the Health Benefits of Cycling Outweigh the Risks?" Environ Health Perspect 118(8).
- This paper presents a systematic literature review of experimental or observational studies that objectively evaluated the effect of the built environment on cycling.
- A total of 21 studies met the inclusion criteria, all of which were observational studies. Eleven studies identified objectively measured environmental factors with a significant positive association with cycling.
- The environmental factors identified as being positively associated with cycling included presence of dedicated cycle routes or paths, separation of cycling from other traffic, high population density, short trip distance, proximity of a cycle path or green space and for children projects promoting ‘safe routes to school’.
- Negative environmental factors were perceived and objective traffic danger, long trip distance, steep inclines and distance from cycle paths.
- Of the seven studies which focused primarily on the impact of cycle routes, four demonstrated a statistically significant positive association.
- Although the study identified environmental factors with positive and negative associations with cycling behavior, many other types of environmental policies and interventions have yet to be rigorously evaluated.
- Policies promoting cycle lane construction appear promising but the socio-demographic distribution of their effects on physical activity is unclear. The wider impact of active transport policies on health and inequalities across Europe must be explored.
Fraser, Simon, Lock, Karen. "Cycling for transport and public health: a systematic review of the effect of the environment on cycling." The European Journal of Public Health. (2010)
- Physical activity (PA) has been hypothesized to spare gray matter volume in late adulthood, but longitudinal data testing an association has been lacking.
- This study tested whether PA would be associated with greater gray matter volume after a 9-year follow-up, a threshold could be identified for the amount of walking necessary to spare gray matter volume, and greater gray matter volume associated with PA would be associated with a reduced risk for cognitive impairment 13 years after the PA evaluation.
- In 299 adults (mean age 78 years) from the Cardiovascular Health Cognition Study, researchers examined the association between gray matter volume, PA, and cognitive impairment. Physical activity was quantified as the number of blocks walked over 1 week.
- High-resolution brain scans were acquired 9 years after the PA assessment on cognitively normal adults. White matter hyperintensities, ventricular grade, and other health variables at baseline were used as covariates.
- Walking amounts ranged from 0 to 300 blocks (mean 56.3; SD 69.7). Greater PA predicted greater volumes of frontal, occipital, entorhinal, and hippocampal regions 9 years later. Walking 72 blocks was necessary to detect increased gray matter volume but walking more than 72 blocks did not spare additional volume. Greater gray matter volume with PA reduced the risk for cognitive impairment 2-fold.
- Greater amounts of walking are associated with greater gray matter volume, which is in turn associated with a reduced risk of cognitive impairment.
Erickson, KI, Raji, CA, Lopez, OL, Becker, JT, Rosano, C, Newman, AB, Gach HM, Thompson, PM, Ho, AJ and Kuller, LH. “Physical Activity Predicts Gray Matter Volume in Late Adulthood: the Cardiovascular Health Study.” Neurology. 75.16 (2010): 1415-1422.
- 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).
- 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.
- This study tests whether a simulated active commute to school dampens cardiovascular reactivity to a cognitive stressor typical to what children might experience during school.
- Forty children (20 girls and 20 boys) aged 10-14 yr were randomly assigned to simulated sedentary drive-to-school or active-commute (walking) groups.
- Children in the walking group had lower heart rate, systolic blood pressure, pulse pressure, and perceived stress reactivities to cognitive stress than the control group.
- Active commuting to school may dampen cardiovascular reactivity and perceived stress when confronted with stressful cognitive challenges during the school day. This may help reduce the risk for cardiovascular disease later in life.
Lambiase, Maya J., Barry, Heather, M., and Roemmich, James N. “Effect of a Simulated Active Commute to School on Cardiovascular Stress Reactivity.” Medicine & Science in Sports & Exercise. 42.8 (2010): 1609-1616.
- This study looks at the magnitude, direction, and statistical significance of the relationship between active travel and rates of physical activity, obesity, and diabetes.
- Researchers examined aggregate cross-sectional health and travel data for 14 countries, all 50 US states, and 47 of the 50 largest US cities through graphical, correlation, and bivariate regression analysis on the country, state, and city levels.
- Researchers found statistically significant negative relationships between active travel and self-reported obesity at all 3 geographic levels.
- At the state and city levels, researchers found statistically significant positive relationships between active travel and physical activity and statistically significant negative relationships between active travel and diabetes.
- This analysis provides additional evidence of the population-level health benefits of active travel.
- Policies on transport, land-use, and urban development should be designed to encourage walking and cycling for daily travel.
Pucher, John, Buehler, Ralph, Bassett, David R., and Dannenberg, Andrew L. “Walking and Cycling to Health: A Comparative Analysis of city, state, and International Data.” American Journal of Public Health. (2010): e1–e7.
- In this systematic review and meta-analysis researchers quantify the dose–response relationship of non-vigorous physical activity and all-cause mortality.
- Researchers found that 2.5 h/week (equivalent to 30 min daily of moderate intensity activity on 5 days a week) compared with no activity was associated with a reduction in mortality risk of 19%, while 7 h/week of moderate activity compared with no activity reduced the mortality risk by 24%. A smaller effect was found in studies that looked at walking alone.
- Researchers conclude that being physically active reduces the risk of all-cause mortality. The largest benefit was found from moving from no activity to low levels of activity, but even at high levels of activity benefits accrue from additional activity.
Woodcock, James, Franco, Oscar H, Orsini Nicola, and Roberts, Ian. “Non-vigorous physical activity and all-cause mortality: systematic review and meta-analysis of cohort studies.” International Journal of Epidemiology. (2010).
- This study examines changes in state-specific obesity and overweight prevalence among US children and adolescents between 2003 and 2007 through a cross-sectional analysis of National Survey of Children’s Health data.
- Results indicate that in 2007, 16.4% of US children were obese and 31.6% were overweight.
- Mississippi has the highest prevalence of childhood obesity and overweight (21.9%) and Oregon has the lowest (9.6%).
- Between 2003 and 2007obesity prevalence increased by 10% for all US children.
- Individual, household, and neighborhood social and built environmental characteristics accounted for 45% and 42% of the state variance in childhood obesity and overweight.
- Researchers suggest that substantial geographic disparities in childhood obesity and overweight exist, indicating potential for considerable reduction in US childhood obesity.
Singh, Gopal K., Kogan, Michael, D., and van Dyck, Peter C. “Changes in State-Specific Childhood Obesity and Overweight Prevalence in the United States From 2003 to 2007.” Archives of Pediatrics and Adolescent Medicine. 164.7 (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.
- Recent research suggests that racial residential segregation may be detrimental to health.
- This study investigates the influence of neighborhood racial isolation on obesity and considers the role of neighborhood disorder as a mediator in this relationship.
- For the city of Philadelphia, researchers find that residence in a neighborhood with high black racial isolation is associated with a higher body mass index and higher odds of obesity among women, but not men, highlighting important sex differences in the influence of neighborhood structure on health.
- The influence of high racial isolation on women’s weight status is mediated, in part, by the physically disordered nature of such neighborhoods. Disorder of a more social nature (as measured by incident crime) is not associated with weight status.
Chang, Virginia W., Hillier, Amy E., and Mehta, Neil K. “Neighborhood Racial Isolation, Disorder and Obesity.” Social Forces. 87.4 (2009): 2063-2092.
- 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.
- 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.
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