Investigation on associations between long-term air pollution exposure and osteoporotic fracture using nationwide cohort study data in South Korea

Abstract

BACKGROUND AND AIM Bone health is a major concern for aging populations globally. Human and animal studies have suggested biological mechanisms for osteoporosis and bone density associated with air pollution, but less is known about the impacts of air pollution on osteoporotic fracture. We examined the associations between long-term air pollution exposure and risk of osteoporotic fracture in adults in seven large Korean cities. METHODS We used Cox proportional hazard models to estimate hazard rations (HRs) of time-varying moving window of past exposures of particulate matter (PM₁₀), sulfur dioxide (SO₂), carbon monoxide (CO), nitrogen dioxide (NO₂), and ozone (O₃) for osteoporotic fracture in Korean adults (age ≥50 years) in the National Health Insurance Service-National Sample Cohort data, followed 2002 to 2015. HRs were calculated for an interquartile range (IQR) increase of 3-year moving average concentration of each pollutant. Data of 56,467 participants over 535,481 person-years of follow-up were used. The model adjusted for individual-level confounders (comorbidity, prescription for osteoporosis, age, sex, body mass index, health behaviors, income). RESULTS Linear and positive exposure-response associations were found for SO₂, while PM₁₀ and NO₂ showed nonlinear associations. SO₂ was associated with osteoporosis-related fracture with marginal significance (HR for an IQR [2 ppb] increase = 1.04, 95% CI: 1.00–1.09). The SO₂ HR estimates were robust in analyses applying various moving windows of exposure (from one to three years of past exposure) and two-pollutant models. The O₃ HR estimate was positive but not significant (HR for 0.007 ppm increase = 1.01, 95% CI: 0.97–1.06). PM₁₀, CO, and NO₂ did not show associations. Vulnerable groups by sex, age, exercise, and income varied across air pollutants and there was no evidence of effect modifications. CONCLUSIONS Long-term exposure to SO₂ was associated with increased osteoporotic fracture risks in Korean adults. KEYWORDS Air pollution, bone fracture, cohort studies, osteoporosis.