The role of air pollution in bone health among adults with overweight and obesity in Spain

Abstract Background Obesity influences fracture risk by increasing bone mineral density (BMD) but reducing bone strength relative to load. Genetics account for less than 10% of BMD variance, so environmental factors warrant further investigation. Air pollution may impair bone health, yet evidence in older adults with excess weight is limited. We examined cross-sectional associations of particulate matter (PM2.5), black carbon (BC), and nitrogen dioxide (NO2), with BMD at the femoral neck, femoral trochanter, total femur, and lumbar spine (L1-L4) in adults with overweight and obesity. Methods The study builds on the PREDIMED-Plus trial, which recruited participants across Spain during 2013-2016. Participants underwent dual-energy x-ray absorptiometry and reported their home address at baseline. Annual air pollution exposures were assigned by linking addresses to hybrid land-use estimates of air pollutant concentrations at 100m resolution. We used BMD T-scores standardized by age, sex, weight, and height. For each exposure-outcome pair, we used linear regression models adjusted for sex, age, study site, physical activity, sedentary time, education, smoking, and dietary calcium, fruit and vegetable intake, and percentage of fat and lean mass. Results We included 891 adults (age: 54-75 years, 50% women) from 4 cities (Pamplona, Palma, Reus, León). In fully adjusted models, a 5 μg/m3 increase in PM2.5 was associated with a -0.21 (95% CI: -0.57 to + 0.14) reduction in lumbar spine BMD and -0.11 (-0.38 to + 0.15) in femoral neck BMD. Positive but non-significant associations were found for femoral trochanter and total femur, and for BC. No associations were observed for NO2. Conclusions Our findings suggest that long-term exposure to PM2.5 may be linked to lower BMD among mature adults with overweight and obesity. Longitudinal studies are needed to confirm these associations, guide preventive strategies, and support public health action in this and other high-risk populations. Key messages • Long-term PM2.5 exposure may weaken bone health in older adults with overweight and obesity, highlighting air pollution as a potential risk factor for osteoporosis. • Findings support integrating bone health into environmental health surveillance and raising awareness of air pollution as a possible modifiable risk factor for skeletal decline.