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News | Science Selection Volume 121 | Issue 09 | September 2013

Environ Health Perspect; DOI: 10.1289/ehp.121-A283

Respiratory Disparity? Obese People May Not Benefit from Improved Air Quality

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Carol Potera, based in Montana, has written for EHP since 1996. She also writes for Microbe, Genetic Engineering News, and the American Journal of Nursing.
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Improved Air Quality and Attenuated Lung Function Decline: Modification by Obesity in the SAPALDIA Cohort

Tamara Schikowski, Emmanuel Schaffner, Flurina Meier, Harish C. Phuleria, Andrea Vierkötter, Christian Schindler, Susi Kriemler, Elisabeth Zemp, Ursula Krämer, Pierre-Olivier Bridevaux, Thierry Rochat, Joel Schwartz, Nino Künzli, and Nicole Probst-Hensch

About a third of U.S. adults and 17% of U.S. children were obese in 2009–2010, according to the Centers for Disease Control and Prevention.1 Obesity is associated with reduced lung function2 and other health conditions, including asthma3,4 and cardiovascular disease.5 Exposure to ambient particulate matter is associated with similar health effects, which may be exacerbated by obesity.6,7

While promoting various types of negative health effects, the effects of obesity also may mask those of beneficial interventions. In this issue of EHP, Swiss researchers report that when air quality improves, so does lung function in adults, but only in people with a low or normal body mass index (BMI).8

The team used data from the Swiss Study on Air Pollution and Lung Disease in Adults (SAPALDIA), a population-based study launched in 1991. The ongoing longitudinal study tracks the respiratory health of several thousand adults who live in eight geographic regions of Switzerland.8

The latest analysis of the SAPALDIA cohort compares spirometry data collected in 1991 and 2002 for 4,664 participants. Lung-function tests included forced expiratory volume in 1 second (FEV1),9 forced vital capacity (FVC),10 and average forced expiratory flow over the middle half of the FVC (FEF25–75).11

The investigators estimated changes in each participant’s average exposure to coarse particulate matter (PM10) outdoors at home between 1991 and 2002 using air quality data and dispersion models developed by the Swiss government. The median PM10 concentration was 5.3 µg/m3 lower in 2002 than in 1991. Air quality improved more in cities than in the alpine regions of Davos and Montana, which had cleaner air to start with.12 Participants’ BMIs were used to assess obesity, with most people gaining weight during the 10-year period.8

Overweight couple outdoors

Improved air quality may not be enough to compensate for lung function reduced as a result of excess weight.

© Corbis

Lung function generally declines with age. In the SAPALDIA cohort this natural age-related decline was slowed in people breathing cleaner air, but only in those with a BMI of less than 24 (i.e., those who were normal- or underweight). Yearly changes in some lung-function parameters, particularly those related to the small airways (such as FEF25–75), were slowed by up to 30% in people with low or normal BMIs. Overweight and obese people showed no benefit to lung function from breathing cleaner air, meaning their annual age-related decline in lung function was not slowed down.8

The results “suggest that attenuation of age-related lung function decline due to improved air quality may be observable only in normal-weight and underweight persons,” conclude the authors.8 The connection needs to be confirmed with more studies that use direct measures of obesity rather than participants’ report of their own weight, says study leader Tamara Schikowski, a research scientist at the Swiss Tropical and Public Health Institute in Basel.

Excess weight is associated with reduced ability of the lung to stretch, which increases the mechanical work needed to breathe.13 Improved air quality may not be enough to compensate for these physical changes in overweight and obese people. Additionally, excess weight14 and air pollution15 are both associated with chronic inflammation and together may be more likely to lead to permanent damage of lung tissue, reducing the benefits of breathing cleaner air, Schikowski suggests.

“The strength of the Swiss study is that the population is large, and standardized spirometric and air pollution data are available,” says Norbert Berend, an emeritus professor and director of Respiratory Research at the George Institute of Global Health, University of Sydney, Australia. The authors’ speculation that systemic inflammation due to obesity may prevent the beneficial effects of reduced pollution “has important implications and needs to be followed up with further studies,” Berend notes.


References and Notes

1. Ogden CL, et al. Prevalence of obesity in the United States, 2009–2010. NCHS Data Brief, No. 82, January 2012. Atlanta, GA:National Center for Health Statistics, U.S. Centers for Disease Control and Prevention (2012). Available: http://www.cdc.gov/nchs/data/databriefs/​db82.pdf [accessed 6 August 2013].

2. Thyagarajan B, et al. Longitudinal association of body mass index with lung function: the CARDIA study. Respir Res 9(1):31 (2008); http://dx.doi.org/10.1186/1465-9921-9-31.

3. Chinn S, et al. Incidence of asthma and net change in symptoms in relation to changes in obesity. Eur Respir J 28(4):763–771 (2006); http://dx.doi.org/10.1183/09031936.06.00150505.

4. Marcon A, et al. Body mass index, weight gain, and other determinants of lung function decline in adult asthma. J Allergy Clin Immunol 123(5):1069–1074 (2009); http://dx.doi.org/10.1016/j.jaci.2009.01.040.

5. Shah AS, et al. Global association of air pollution and heart failure: a systematic review and meta-analysis. Lancet; http://dx.doi.org/ 10.1016/S0140-6736(13)60898-3 [online 10 July 2013].

6. Lu KD, et al. Being overweight increases susceptibility to indoor pollutants among urban children with asthma. J Allergy Clin Immunol 131(4):1017–1023 (2013); http://dx.doi.org/10.1016/j.jaci.2012.12.1570.

7. Kannan S, et al. Exposure to fine particulate matter and acute effects on blood pressure: effect modification by measures of obesity and location. J Epidemiol Community Health 64(1):68–74 (2010); http://dx.doi.org/10.1136/jech.2008.081836.

8. Schikowski T, et al. Improved air quality and attenuated lung function decline: modification by obesity in the SAPALDIA cohort. Environ Health Perspect 121(9):1034–1039 (2013); http://dx.doi.org/10.1289/ehp.1206145.

9. FEV1 is a measure of the most air that can be forcefully expired in 1 second.

10. FVC is a measure of the most air that can be expired after taking the deepest breath possible.

11. FEF25, FEF50, and FEF75 are measures of the speed at which air exits the lung when 25%, 50%, and 75% of the FVC, respectively, remains in the lung.

12. Liu LJS, et al. Characterization of source-specific air pollution exposure for a large population-based Swiss cohort (SAPALDIA). Environ Health Perspect 115(11):1638–1645 (2007); http://dx.doi.org/10.1289/ehp.10177.

13. Salome CM, et al. Physiology of obesity and effects on lung function. J Appl Physiol 108(1):206–211 (2010); http://dx.doi.org/10.1152/japplphysiol.00694.2009.

14. Medoff BD, et al. Adiponectin deficiency increases allergic airway inflammation and pulmonary vascular remodeling. Am J Respir Cell Mol Biol 41(4):397–406 (2009); http://dx.doi.org/10.1165/rcmb.2008-0415OC.

15. Ferecatu I, et al. Polycyclic aromatic hydrocarbon components contribute to the mitochondria-antiapoptotic effect of fine particulate matter on human bronchial epithelial cells via the aryl hydrocarbon receptor. Part Fibre Toxicol 7(1):18 (2010); http://dx.doi.org/10.1186/1743-8977-7-18.


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