Air pollution and bone fractures in a high-risk population: differences by age and sex

Fracture incidence is high in Norway compared to other European countries. We examined whether ambient air pollution levels are associated with forearm and hip fracture incidence, and whether these associations differed by sex and age.

Register data on 127,799 forearm fractures (age ≥40 years) and 103,754 hip fractures (age ≥50 years) were linked to population data from Statistics Norway (2008-2018). Annual levels of particulate matter <2.5 µm (PM_2.5) and nitrogen dioxide (NO₂) were modelled in the NordicWelfAir project using the Urban Background Model and combined via ArcGIS. Fracture Incidence Rate Ratios (IRRs) with 95% Confidence Intervals (CIs) by pollutant levels were estimated using Poisson regression, adjusting for education level, marital status, and immigrant background, urban/rural and inland location, health region, and climate, and examining interactions by sex and age (multiplicative and additive).

PM_2.5 ranged from 0.90-66.1  µg/m³ (mean: 5.5) and NO₂ from 0.20-72.2  µg/m³ (mean: 8.1). In the highest PM_2.5 tertile compared to the lowest, age- and year-adjusted forearm fracture risk was IRR = 1.22 (95% CI: 1.18, 1.25) in men and IRR = 1.24 (95% CI: 1.22, 1.26) in women. They were partly attenuated after adjusting for annual temperature and geographic variables. Associations with NO₂ and with hip fractures were similar, though weaker. Interactions by sex and age were present for both fracture types, most notably a stronger NO₂- hip fracture association in individuals aged ≥80 years.

Ambient air pollution is associated with fracture risk, even at low exposure levels. The most consistent finding was a stronger association among individuals aged 80 years and above.