Background
Air particulate matter (PM) is a ubiquitous environmental exposure associated with oxidation, inflammation, and age-related chronic disease. Whether PM is associated with loss of bone mineral density (BMD) and risk of bone fractures is undetermined.
Methods
We conducted two complementary studies of: (i) long-term PM <2.5 μm (PM2.5) levels and osteoporosis-related fracture hospital admissions among 9.2 million Medicare enrollees of the Northeast/Mid-Atlantic United States between 2003–2010; (ii) long-term black carbon [BC] and PM2.5 levels, serum calcium homeostasis biomarkers (parathyroid hormone, calcium, and 25-hydroxyvitamin D), and annualized BMD reduction over a 8-year follow-up of 692 middle-aged (46.7±12.3 yrs), low-income BACH/Bone cohort participants.
Findings
In the Medicare analysis, risk of bone fracture admissions at osteoporosis-related sites was greater in areas with higher PM2.5 levels (Risk ratio [RR] 1.041, 95% Confidence Interval [CI], 1.030, 1.051). This risk was particularly high among low-income communities (RR 1.076; 95% CI, 1.052, 1.100). In the longitudinal BACH/Bone study, baseline BC and PM2.5 levels were associated with lower serum PTH (Estimate for baseline one interquartile increase in 1-year average BC= −1.16, 95% CI −1.93, −0.38; Estimate for baseline one interquartile increase in 1-year average PM2.5= −7.39; 95%CI −14.17, −0.61). BC level was associated with higher BMD loss over time at multiple anatomical sites, including femoral neck (−0.08%/year per one interquartile increase; 95% CI −0.14, −0.02%/year) and ultradistal radius (−0.06%/year per one interquartile increase; 95% CI −0.12, −0.01%/year).
Interpretation
Our results suggest that poor air quality is a modifiable risk factor for bone fractures and osteoporosis, especially in low-income communities.