Background
Air pollution has been increasingly recognized as a significant environmental risk factor for metabolic diseases, including obesity and metabolic syndrome. Previous studies have linked exposure to pollutants like black carbon (BC), fine particulate matter (PM2.5), and nitrogen dioxide (NO2) to cardiovascular and metabolic dysregulation. However, the longitudinal impact of air pollution on body composition, particularly in older adults with metabolic syndrome, remains underexplored. This study addresses this gap by examining the relationship between long-term air pollution exposure and changes in total fat mass, visceral fat mass, and lean mass over three years.
Study Design
The study included 1,454 older adults (aged 54-75 years; 48% female) from the PREDIMED-Plus trial in Spain. Participants underwent baseline dual-energy X-ray absorptiometry (DXA) scans at recruitment (2013-2016) and at 1- and 3-year follow-up. Annual air pollution exposure was assigned at participants’ baseline residential addresses at a 100-meter resolution. Linear mixed-effect regression models with interaction terms for exposure and time were used to examine longitudinal associations with body composition. Stratified analyses by sex, age, and physical activity were also conducted.
Key Findings
At baseline, a 1×10-5/m increase in black carbon (BC) was associated with a 1.01% (95% CI 0.31-1.71) higher body fat percentage, a -0.97% (95% CI -1.64 to -0.30) lower lean mass percentage, and a -0.74 kg (95% CI -1.37 to -0.12) lower lean mass. Similar relationships were observed for PM2.5 and NO2 with body fat and lean mass percentage. These associations persisted at the 1- and 3-year follow-ups for BC and PM2.5. Age-stratified analyses revealed that associations with visceral fat mass were significant only in participants younger than 65 years. No meaningful differences were observed by sex or physical activity levels.
Expert Commentary
The findings underscore the detrimental effects of long-term air pollution on body composition, particularly in metabolically vulnerable older adults. The persistence of these associations over three years suggests that air pollution may contribute to chronic metabolic dysregulation. The age-specific effects on visceral fat mass highlight the need for targeted interventions in younger older adults. Study limitations include the observational design, which precludes causal inferences, and the potential for residual confounding. Nonetheless, the high-resolution exposure assessment and longitudinal follow-up strengthen the findings.
Conclusion
Long-term exposure to air pollution is adversely associated with body composition changes in older adults with metabolic syndrome, promoting fat accumulation and lean mass loss over time. These findings call for public health strategies to mitigate air pollution exposure in vulnerable populations. Future research should explore mechanistic pathways and potential interventions to counteract these effects.
Funding and Registration
The study was part of the PREDIMED-Plus trial. Funding details and clinical trial registration information were not provided in the abstract.