Exposure to more air pollution may increase incident fracture risk among older adults
Click Here to Manage Email Alerts
Key takeaways:
- Exposure to small air particulate matter, nitrogen dioxide and other nitrogen oxides is linked to a higher risk for incident fractures.
- Adults exposed to more air pollution had lower serum 25-(OH)D levels.
Middle-aged and older adults who live in areas with greater air pollution may have a higher risk for incident fractures, according to a study published in the Journal of Bone and Mineral Research.
In an analysis of data from the UK Biobank, adults who sustained an incident fracture were living in areas of the U.K. with greater levels of air particulate matter of less than 2.5 µm (PM2.5), nitrogen dioxide and nitrogen oxides compared with adults who did not have a fracture. Additionally, the risk for an incident fracture climbed with increasing exposure to air pollution.
“Those findings indicated that air particulate matter and nitrogen oxides might, indirectly or directly, undermine osteal health and induce fracture pathophysiology,” Yan Zheng, MD, PhD, professor in the department of cardiology at Zhongshan Hospital and in the State Key Laboratory of Genetic Engineering, School of Life Sciences and Human Phenome Institute at Fudan University in Shanghai, and colleagues wrote.
Researchers obtained data from 446,395 adults aged 40 to 69 years who participated in the UK Biobank from 2006 to 2010. Mean annual concentrations of particulate matter and nitrogen oxides were calculated at different residential areas. Home addresses for each participant were obtained to calculate residential level air pollution exposure. Incident fractures were obtained from hospital admission records. Incident fractures included new-onset clinical hip fractures, clinical vertebral fractures and other clinical fractures. Hospital admission data were collected up to March 31, 2017. Confounders were obtained from baseline questionnaires. Serum 25-hydroxyvitamin D levels were measured in each participant.
Small air particulate matter, nitrogen oxide exposure increase fracture risk
There were 12,288 incident fractures that occurred during a median 8 years of follow-up. Adults who sustained a fracture lived in places with a higher level of PM2.5 and nitrogen oxides than those who did not sustain a fracture (P < .05 for all). Exposure to PM2.5-10 was not associated with a difference in fracture risk, and adults without fractures were exposed to more PM10 than those who sustained a fracture (P = .01).
Each 10 µg/m3 exposure to PM2.5 was associated with a 70% increased risk for an incident fracture in a fully adjusted model (HR = 1.7; 95% CI, 1.42-2.03). There were no increased risks for fractures with increased exposure to PM2.5-10 or PM10. Each 10 µg/m3 exposure to nitrogen dioxide (HR = 1.08; 95% CI, 1.06-1.1) or nitrogen oxides (HR = 1.04; 95% CI, 1.03-1.05) was associated with a higher risk for a fracture. Similar findings were observed when adults were divided into quintiles by air pollution exposure.
Air pollution exposure linked to lower serum 25-(OH)D levels
Each 10 µg/m3 exposure to PM2.5 (beta = –9.66 nmol/L; 95% CI, –10.2 to –9.11), PM10 (beta = –1.36 nmol/L; 95% CI, –1.65 to –1.07), nitrogen dioxide (beta = –1.19 nmol/L; 95% CI, –1.25 to –1.13) and nitrogen oxide (beta = –0.71 nmol/L; 95% CI, –0.75 to –0.68) was associated with reductions in serum 25-(OH)D level. In mediation analysis, serum 25-(OH)D level accounted for 5.96% of the estimated effect of PM2.5 on fracture risk, 2.55% of the estimated effect of PM10 on fracture risk, 4.09% of the estimated effect of nitrogen dioxide on fracture risk and 5.45% of the estimated effect of nitrogen oxides on fracture risk.
“Small particulates could settle in the alveoli and circulate compositional heavy metals into the bone metabolism matrix,” the researchers wrote. “Nitrite, as the byproduct of inhaled nitrogen oxides, could also enter the circulation system and bind to hemoglobin, resulting in metabolic disorders. Our mediation analysis indicated that around 4% to 6% of air particulate matter and nitrogen oxides effects on incident fractures were mediated by serum 25-(OH)D. These air particulate matter and nitrogen oxides that can irritate the alveoli wall may be involved in the same serum 25-(OH)D-altering pathway.”
The researchers said further studies must be conducted to examine whether alcohol consumption or eating fresh fruit could help reduce the risk for fractures for people living in areas with greater air pollution.
Collapse
Click Here to Manage Email Alerts