Long-term exposure to ambient air pollution and risk of non-traumatic osteonecrosis of the femoral head: A nationwide cohort study.

Abstract

Non-traumatic osteonecrosis of the femoral head (ONFH) results from chronic ischemia and impaired bone remodeling, but whether long-term air pollution contributes to its development remains unclear. This study evaluated the association between chronic exposure to ambient air pollutants and the risk of ONFH in a nationwide cohort. We analyzed 585,334 adults from Taiwan's Longitudinal Health Insurance Database 2000, followed from 1993 to 2013. Ten-year cumulative exposures to sulfur dioxide (SO₂), carbon monoxide (CO), particulate matter ≤2.5 μm (PM₂.₅) and ≤ 10 μm (PM₁₀), nitrogen oxides (NOX, NO, NO₂), total hydrocarbons (THC), non-methane hydrocarbons (NMHC), and methane (CH₄) were estimated using residential postal codes linked to environmental monitoring data. Cox proportional-hazards models were applied to estimate adjusted hazard ratios (HRs) for incident ONFH, with Bonferroni correction applied in sensitivity analyses. Prolonged exposure to all pollutants was significantly associated with higher ONFH incidence. Adjusted HRs (95% CI) per standard-deviation increase were: SO₂ 1.31 (1.23-1.39), CO 1.78 (1.69-1.86), PM₂.₅ 1.76 (1.63-1.90), PM₁₀ 1.44 (1.33-1.55), NOX 1.56 (1.47-1.65), NO 1.40 (1.32-1.48), NO₂ 1.59 (1.49-1.69), THC 1.64 (1.55-1.72), NMHC 1.18 (1.11-1.24), and CH₄ 2.15 (2.02-2.29). Tertile analyses demonstrated consistent dose-response trends, with highest-tertile associations remaining significant after Bonferroni correction. Long-term exposure to multiple ambient pollutants is associated with an increased risk of non-traumatic ONFH. These findings highlight air pollution as a modifiable environmental determinant of musculoskeletal health and emphasize the need for continued efforts to improve air-quality standards.