Background Environmental air pollution has been associated with disruption of bone health at a molecular level. Particulate matter (PM) exposure can simultaneously stimulate bone resorption and halt bone formation.

Objectives The primary aim of the present study is to describe the association between long-term exposure to PM and osteoporosis in a large cohort of women at high risk of fracture.

Methods Clinical, demographic and densitometric data were extracted from the DeFRAcalc79 dataset, which gathers data on women at risk for osteoporosis. Data on the monitoring of PM10 and PM2.5 concentrations were retrieved from the Italian institute of environment protection and research (Istituto Superiore per la Protezione e la Ricerca Ambientale, ISPRA). Every study subject was linked to a PM exposure value, which resulted from the average concentration of urban, rural and near-traffic stations of the subject residency (ZIP code centroids 25 km) from January 2013 to December 2019. Generalized linear models with robust estimators were employed to determine the relationship between BMD and PM long-term exposure. We sequentially adjusted for confounders. Model 1 included age, body mass index (BMI), presence of prevalent fragility fractures, family history of vertebral or hip fractures, and menopause. Model 2 was further adjusted for glucocorticoid treatment and comorbidities. Model 3 (main model) added to model 2 the macro-area of residency (stratified as a categorical variable: northern Italy, central Italy and southern Italy).

Results 59,950 women from 110 Italian provinces were included in the study. PM 2,5 exposure was negatively associated with T-score levels at the femoral neck (β -0.005, 95 CI -0.007 to -0.003) and lumbar spine (β -0.003, 95% CI -0.006 to -0.001). Chronic exposure to PM2.5 above 25 μg/m³ was associated with a 16% higher risk of having osteoporotic T-score at any site (aOR 1.161, 95% CI 1.105 to 1.220), exposure to PM10 above 30 μg/m³ was associated with a 15% higher risk of having osteoporotic T-score at any site (aOR 1.148, 95% CI 1.098 to 1.200).

Conclusion Long-term exposure to air pollution was associated with higher risk of osteoporosis. Femoral neck site seemed to be more susceptible to the detrimental effect of PM exposure than lumbar spine site.

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Disclosure of Interests Giovanni Adami Shareholder of: Galapagos, Theramex, Camilla Benini: None declared, Angelo Fassio: None declared, Eugenia Bertoldo: None declared, Ombretta Viapiana: None declared, Davide Gatti: None declared, Maurizio Rossini Shareholder of: Abbvie, Amgen, Bms, Eli Lilly, Galapagos, Novartis, Pfizer, Sandoz, Theramex, Ucb.