New Study: High Levels of Air Pollution Associated with Lower Levels of Physical Activity

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Today’s post comes from Dr Jennifer D Roberts.  You can find more on Jennifer at the bottom of this post.

Physical inactivity, ambient air pollution and obesity are modifiable risk factors for non-communicable diseases, with the first accounting for more than three million annual deaths.  Recently, we identified an association between increased ambient air pollution, specifically particulate matter 2.5 (PM2.5), and reduced leisure-time physical activity within the U.SNumerous scientific studies have linked PM2.5 exposure to a variety of health problems including irregular heartbeat, aggravated asthma, and premature death.  However, many of these studies have illustrated these effects in a resting, inactive state, or among elite athletes and the data examining the effects of poor air quality among larger individuals or in real-world physically active settings are meager.

Figure 1. Pollution in the USA (Roberts et al., PLOS ONE)

Figure 1. PM 2.5 Air pollution in the USA.  Darker blue represents higher levels of pollution. (Roberts et al., PLOS ONE)

Figure 2

Figure 2. Prevalence of leisure-time physical inactivity. Darker orange represents higher level of physical inactivity.

 

This research found that the highest concentrations of PM2.5 were in the upper Atlantic, Midwest, and the South, along with a small cluster in Southern California (Figure 1).  By comparison, Figure 2 shows the unweighted prevalence of leisure-time physical inactivity in U.S. counties.  Both maps illustrate higher levels of PM2.5 and leisure-time physical inactivity in the South and Midwest.  

Our study findings were compelling because they indicated that the magnitude of this inverse association between air pollution and physical activity was more pronounced among the normal or healthy weight, as opposed to overweight or obese individuals.  Specifically, for these leaner individuals, we estimated a 16–35% relative increase in the odds of leisure-time physical inactivity per exposure class increase of PM2.5 after controlling for several variables, such as age, sex, race, income, seasonality, and urbanization (Figure 3).  We recently published our findings in PLOS ONE this past March (DOI: 10.1371/journal.pone.0090143).

Odds of Physical Inactivity By Pollution Exposure and Body Weight.  Data are adjusted for adjusted for age, sex, race/ethnicity, education, annual income, marital status, seasonality, geographic region, general health status, smoking, disability, asthma, urbanization, and the other air pollutants. (Robertson et al., PLOS ONE)

Figure 3. Odds of Physical Inactivity By  PM 2.5 Air Pollution Exposure and Body Weight. Data are adjusted for age, sex, race/ethnicity, education, annual income, marital status, seasonality, geographic region, general health status, smoking, disability, asthma, urbanization, and the other air pollutants. (Robertson et al., PLOS ONE)

To do this research, we assessed leisure-time physical inactivity using individual self-reported survey data from the Centers for Disease Control and Prevention.  Using the county of residence as a common linkage, we then combined these data with U.S. Environmental Protection Agency air pollution data using statistical software and geographic information systems.  Finally, in our statistical analysis, we evaluated whether those exposed to higher levels of air pollution were less active while also stratifying by body weight category.

Although a causal mechanism cannot be elucidated by our study design, the association of leisure-time physical inactivity and ambient air pollution as mediated by body weight category is plausible.  Given the public health emphasis on community level determinants of physical inactivity, additional research should determine if environmental air pollution is a modifiable risk factor for inactivity. The results of our study provide some insight that this is an area of research that is worth pursing with additional investigations.

DISCLAIMER:

This work is the sole responsibility of the authors and does not represent the official views of the Uniformed Services University of the Health Sciences or Department of Defense.

 

Dr Jennifer Roberts

Dr Jennifer Roberts

About the Author: Jennifer D. Roberts, DrPH, MPH is an Assistant Professor at Uniformed Services University of the Health Sciences.  Her research investigates the relationship and impact of the built environment on intermediary (e.g., physical inactivity) and outmost (e.g., obesity) health outcomes in both children and adults.  She is also an avid lover of exercise and physical fitness.

 

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