Associations of air pollution, obesity and cardiometabolic health in young adults: The Meta-AIR study

Abstract

Objective: Growing evidence indicates exposure to air pollution contributes to obesity and cardiometabolic disease risk in children and adults, however studies are lacking in young adulthood, an important transitional period in the life course. The aim of this study was to examine the associations of short- and long-term regional ambient and near-roadway air pollution (NRAP) exposures on adiposity and cardiometabolic health in young adults aged 17-22 years.

Methods: From 2014 to 2018, a subset of participants (n = 158) were recruited from the Children's Health Study to participate in the Meta-AIR (Metabolic and Asthma Incidence Research) study to assess obesity (body composition and abdominal adiposity) and cardiometabolic health (fasting glucose, fasting insulin and lipid profiles) measures. Prior 1-month and 1-year average air pollution exposures were calculated from residential addresses. This included nitrogen dioxide (NO₂), ozone (O₃), particulate matter with aerodynamic diameter < 10 μm (PM₁₀), particulate matter with aerodynamic diameter < 2.5 μm (PM_2.5) and NRAP (freeway, non-freeway, and total nitrogen oxides (NO_x)) exposures. Linear regression models examined associations of prior 1-month (short-term) and 1-year (long-term) air pollution exposures on obesity and cardiometabolic factors adjusting for covariates and past childhood air pollution exposures.

Results: In the Meta-AIR study, we conducted a comprehensive analysis with short- and long-term regional ambient and NRAP exposures (in both single- and multi-pollutant models) and obesity- and cardiometabolic-related outcomes and found associations with a few outcomes. A 1 standard deviation (SD) change in long-term NO₂ exposure was associated with a 11.3 mg/dL higher level of total cholesterol (p = 0.04) and 9.4 mg/dL higher level of low-density lipoproteins (LDL)-cholesterol (p = 0.04). Amongst obese participants, associations between long-term NO₂ and total cholesterol and LDL-cholesterol were 4.5 and 9 times larger than the associations in non-obese participants (p_interaction = 0.008 and 0.03, respectively). Additionally, we observed a statistically significant association with increased short-term O₃ exposure and higher triglyceride and very-low-density lipoprotein (VLDL) cholesterol levels (p = 0.04), lower high-density lipoprotein (HDL) cholesterol levels (p = 0.03), and higher hepatic fat levels (p = 0.02). Amongst glucose-related factors, long-term PM_2.5 exposure was associated with higher levels of insulin area under the curve (p = 0.03). There were no other statistically significant associations with short- or long-term air pollutants and BMI, other measures of adiposity, and cardiometabolic outcomes.

Conclusion: Higher exposure to regional air pollutants, namely prior 1-year average NO₂, was associated with higher fasting serum lipid measures. These associations were more pronounced in obese participants, suggesting obesity may exacerbate the effects of air pollution exposure on lipid levels in young adults. This study did not find any other associations between short- and long-term ambient and NRAP exposures across a range of other obesity and cardiometabolic indicators. Further studies in young adults are warranted as our study suggests potential deleterious associations of both short- and long-term air pollution exposures and lipid metabolism.

Keywords: Ambient air pollution; Cardiometabolic health; Near-roadway air pollution; Obesity; Young adult.

Figure 1.. Meta-AIR Study^a Flow

^aMeta-AIR subjects were recruited between 2014–2018 from Children’s Health Study to examine the effects of short- and long-term ambient and near-roadway air pollution exposures on obesity and cardiometabolic health in young adults.

Figure 2.. Associations^a of Prior 1-Year NO₂ Exposures and Lipid Metabolism Measures by Obesity Status in 158 Participants Enrolled in the Meta-AIR Study from 2014–2018.

NO₂= nitrogen dioxide; HDL= high-density lipoprotein; LDL= low-density lipoprotein; VLDL= very low-density lipoprotein; obese= BMI ≥ 30.0 kg/m², non-obese= BMI< 30.0 kg/m². ^aAssociations reflect change in outcome measure (association estimate (β)) scaled to 1 standard deviation of prior 1-year average ambient NO₂ with 3.9 ppb stratified by obesity status (non-obese vs obese). ^bLinear regression model was used to estimate the associations of 1-year NO₂ and lipid metabolism outcomes after adjusting for age, sex, race/ethnicity, occupational status of subject, parental education, self-reported exercise, current cigarette smoking, e-cigarette use, total body fat percent, diet, season, and historic air pollution exposure. *p<0.05