Incidence of osteoporosis and ambient air pollution in South Korea: a population-based retrospective cohort study

Association between particulate air pollution, physical activity, and the risk of osteoporosis in the UK Biobank

As a major threat to global health, particulate air pollution has a great possibility of affecting bone metabolism. However, the results of limited studies examining the association between particulate air pollution and bone mineral density (BMD) as well as incident osteoporosis (OP) are conflicting, and the role of physical activity in the association above remains to be further studied. We evaluated the relationship between long-term exposure to Black Carbon (BC) and Particulate Matter (PM) (including PM1 (particles with aerodynamic diameter < 1 μm), PM2.5 (particles with aerodynamic diameter < 2.5 μm) and PM10 (particles with aerodynamic diameter < 10 μm)) and BMD together with OP risks, based on a total of 233,184 subjects from the UK Biobank. General linear regression, logistic regression and restricted cubic spline (RCS) methods were adopted to measure both linear and nonlinear relationship between particulate air pollution and BMD and OP prevalence. Stratified analyses were further utilized to evaluate the potential protective effect of physical activity on bone health under particulate air pollution exposure. BC, PM1 and PM2.5 exposure were negatively associated with BMD (BC: β = -2.35E-03, P = 1.78E-02; PM1: β = -1.57E-03, P = 9.04E-04; PM2.5: β = -9.38E-04; P = 2.98E-13) and positively associated with OP risk (BC: OR (95 %CI) = 1.300 (1.150,1.480), P < 0.001; PM1: OR (95 %CI) = 1.100 (1.040,1.170), P < 0.001; PM2.5: OR (95 %CI) = 1.020 (1.000,1.040), P = 0.019). The RCS analysis presented non-linear relationships between all included particulate air pollutants and incident OP. Higher intensity physical activity could alleviate the risks of BMD decline and OP prevalence caused by particulate air pollution. Our study concluded that particulate air pollution is a crucial threat to bone health, the effect of which can be receded by physical activity. Strengthening air pollution control measures and promoting public engagement in physical activity will contribute to reducing the disease burden associated with OP.

Association of long-term exposure to ambient air pollution with osteoporosis among cancer survivors: Results from the Korea National Health and Nutrition Examination Survey

INTRODUCTION

Recent studies suggest that ambient air pollution may contribute to osteoporosis; however, research focusing on populations with greater susceptibility is lacking. This study seeks to explore the association between air pollution and osteoporosis focusing on cancer survivors.

MATERIALS AND METHODS

We analyzed data from 8977 individuals (2245 cancer survivors, 6732 cancer-free population) obtained from the Korea National Health and Nutrition Examination Survey (KNHANES) during 2007-2009 and 2015-2021. Air pollution exposures to PM10, PM2.5, SO₂, NO₂, and CO were estimated using air quality models and satellite data. Moving average concentrations over 1-3 years prior to the survey were calculated. Logistic regression models adjusting for demographic and lifestyle factors were used to assess the association between air pollution and osteoporosis status. Analyses were stratified by cancer survivorship status and sex.

RESULTS

Among cancer survivors, particularly female cancer survivors, higher long-term exposure to air pollutants was associated with greater odds of osteoporosis. Cancer survivors exposed to higher PM10 over 1-, 2-, and 3-year periods had greater odds of osteoporosis (all p < 0.05). In female cancer survivors, 1-year exposure to PM2.5 was associated with 25 % higher odds of osteoporosis (OR = 1.25, 95 % CI = 1.02-1.54), and NO₂ exposure showed a similar association (OR = 1.42; 95 % CI = 1.06-1.90). These associations were not observed in the individuals without cancer history.

CONCLUSION

The association between air pollution and osteoporosis was observed in cancer survivors, especially among female cancer survivors. Our findings emphasize the need for targeted interventions for at-risk populations such as cancer survivors.

Fine particulate matter and osteoporosis: evidence, mechanisms, and emerging perspectives

Air pollution, particularly fine particulate matter with an aerodynamic diameter of ≤2.5 μm (PM2.5), has been recognized for its adverse effects on multiple organs beyond the lungs. Among these, the bone began to garner significant attention. This review covers epidemiological, animal, and cell studies on PM2.5 exposure and bone health as well as studies on PM2.5-induced diseases with skeletal complications. Emerging evidence from epidemiological studies indicates a positive association between PM2.5 exposure and the incidence of osteoporosis and fractures, along with a negative association with bone mineral density. Experimental studies have demonstrated that PM2.5 can disrupt the metabolic balance between osteoclasts and osteoblasts through inflammatory responses, oxidative stress, and endocrine disruption, thereby triggering bone loss and osteoporosis. Additionally, this review proposes a secondary mechanism by which PM2.5 may impair bone homeostasis via pathological alterations in other organs, offering new perspectives on the complex interactions between environmental pollutants and bone health. In conclusion, this contemporary review underscores the often-overlooked risk factors of PM2.5 in terms of its adverse effects on bone and elucidates the mechanisms of both primary and secondary toxicity. Further attention should be given to exploring the molecular mechanisms of PM2.5-induced bone impairment and developing effective intervention strategies.

Association Between Air Pollution and Osteoporosis with High-Risk Populations: A Narrative Review

PURPOSE OF REVIEW

Air pollution has been raised as a novel risk factor for osteoporosis, which impose a huge burden on both individuals and society. Thus, summarizing and discussing previous results on the association between ambient air pollution and osteoporosis can be informative in synthesizing the current evidence and improving relevant action plans.

RECENT FINDINGS

Recent studies reported that long-term exposure to ambient air pollution is associated with an increased risk of osteoporosis and related outcomes; however, the studied populations, air pollutants, areas, and results on high-risk populations are heterogeneous. Among air pollutants, long-term exposure to PM2.5 showed an association with osteoporosis or osteoporosis-related fracture in general. Recent scientific evidence indicates that ambient air pollution is a potential risk factor for osteoporosis and related outcomes. Further research is warranted on how air pollution impacts these outcomes including for high-risk populations with consistent effect modifiers, and analytic methodologies.

A comprehensive review on endocrine toxicity of gaseous components and particulate matter in smog

Smog is a form of extreme air pollution which comprises of gases such as ozone, sulfur dioxide, nitrogen and carbon oxides, and solid particles including particulate matter (PM2.5 and PM10). Different types of smog include acidic, photochemical, and Polish. Smog and its constituents are hazardaous to human, animals, and plants. Smog leads to plethora of morbidities such as cancer, endocrine disruption, and respiratory and cardiovascular disorders. Smog components alter the activity of various hormones including thyroid, pituitary, gonads and adrenal hormones by altering regulatory genes, oxidation status and the hypothalamus-pituitary axis. Furthermore, these toxicants are responsible for the development of metabolic disorders, teratogenicity, insulin resistance, infertility, and carcinogenicity of endocrine glands. Avoiding fossil fuel, using renewable sources of energy, and limiting gaseous discharge from industries can be helpful to avoid endocrine disruption and other toxicities of smog. This review focuses on the toxic implications of smog and its constituents on endocrine system, their toxicodynamics and preventive measures to avoid hazardous health effects.

Long-term air pollution and adverse meteorological factors might elevate the osteoporosis risk among adult Chinese

Objective

This study aims to investigate the relationship between exposure to air pollution and adverse meteorological factors, and the risk of osteoporosis.

Methods

We diagnosed osteoporosis by assessing bone mineral density through Dual-Energy X-ray absorptiometry in 2,361 participants from Jiangsu, China. Additionally, we conducted physical examinations, blood tests, and questionnaires. We evaluated pollution exposure levels using grid data, considering various lag periods (ranging from one to five years) based on participants' addresses. We utilized logistic regression analysis, adjusted for temperature, humidity, and individual factors, to examine the connections between osteoporosis and seven air pollutants: PM₁, PM₂.₅, PM₁₀, SO₂, NO₂, CO, and O₃. We assessed the robustness of our study through two-pollutant models and distributed lag non-linear models (DLNM) and explored susceptibility using stratified analyses.

Results

In Jiangsu, China, the prevalence of osteoporosis among individuals aged 40 and above was found to be 15.1%. A consistent association was observed between osteoporosis and the five-year average exposure to most pollutants, including PM₂.₅, PM₁₀, CO, and O₃. The effects of PM₁₀ and CO remained stable even after adjusting for the presence of a second pollutant. However, the levels of PM₁ and PM₂.₅ were significantly influenced by O₃ levels. Individuals aged 60 and above, those with a BMI of 25 or higher, and males were found to be more susceptible to the effects of air pollution. Interestingly, males showed a significantly higher susceptibility to PM₁ and PM₂.₅ compared to females. This study provides valuable insights into the long-term effects of air pollution on osteoporosis risk among the adult population in China.

Conclusion

This study indicates a potential association between air pollutants and osteoporosis, particularly with long-term exposure. The risk of osteoporosis induced by air pollution is found to be higher in individuals aged 60 and above, those with a BMI greater than 25, and males. These findings underscore the need for further research and public health interventions to mitigate the impact of air pollution on bone health.

Ambient PM2.5 Components Are Associated With Bone Strength: Evidence From a China Multi-Ethnic Study

CONTEXT

The relationship between the components of particulate matter with an aerodynamic diameter of 2.5 or less (PM2.5) and bone strength remains unclear.

OBJECTIVE

Based on a large-scale epidemiologic survey, we investigated the individual and combined associations of PM2.5 and its components with bone strength.

METHODS

A total of 65 906 individuals aged 30 to 79 years were derived from the China Multi-Ethnic Cohort Annual average concentrations of PM2.5 and its components were estimated using satellite remote sensing and chemical transport models. Bone strength was expressed by the calcaneus quantitative ultrasound index (QUI) measured by quantitative ultrasound. The logistic regression model and weighted quantile sum method were used to estimate the associations of single and joint exposure to PM2.5 and its components with QUI, respectively.

RESULTS

Our analysis shows that per-SD increase (μg/m3) in 3-year average concentrations of PM2.5 (mean difference [MD] -7.38; 95% CI, -8.35 to -6.41), black carbon (-7.91; -8.90 to -6.92), ammonium (-8.35; -9.37 to -7.34), nitrate (-8.73; -9.80 to -7.66), organic matter (-4.70; -5.77 to -3.64), and soil particles (-5.12; -6.10 to -4.15) were negatively associated with QUI. In addition, these associations were more pronounced in men, and people older than 65 years with a history of smoking and chronic alcohol consumption.

CONCLUSION

We found that long-term exposure to PM2.5 and its components may lead to reduced bone strength, suggesting that PM2.5 and its components may potentially increase the risk of osteoporosis and even fracture. Nitrate may be responsible for increasing its risk to a greater extent.

Exposure to Neighborhood Walkability and Residential Greenness and Incident Fracture

IMPORTANCE

Emerging studies have suggested that environmental factors are associated with fracture. However, little is known about the association of neighborhood walkability and residential greenness with fracture.

OBJECTIVE

To investigate the association of long-term exposure to walkability and greenness with incident fracture and explore the potential interaction effect.

DESIGN, SETTING, AND PARTICIPANTS

This cohort study recruited participants aged 40 years or older in Ningbo, China from June 2015 to January 2018. Participants were observed for outcomes through February 2023, with data analysis conducted in March 2023.

EXPOSURES

Neighborhood walkability was measured by a modified walkability calculation method according to a walk score tool. Residential greenness was assessed by satellite-derived normalized difference vegetation index (NDVI) within a 1000-m buffer.

MAIN OUTCOMES AND MEASURES

Incident fracture was ascertained according to International Statistical Classification of Diseases and Related Health Problems, Tenth Revision codes via the Yinzhou Health Information System. Cox proportional hazards models were fit, with age as time scale to estimate the associations of walkability and greenness with fracture. Potential effect modification was explored by covariates, as well as the interactive effect of walkability and greenness.

RESULTS

A total of 23 940 participants were included in this study with 13 735 being female (57.4%). The mean (SD) age at baseline was 63.4 (9.4) years. During a follow-up period of 134 638 person-years, 3322 incident fractures were documented. In the full adjusted model, every IQR increment in neighborhood walkability and residential greenness was associated with a hazard ratio (HR) of 0.88 (95% CI, 0.83-0.92) and 0.84 (95% CI, 0.80-0.89), respectively, for fracture. Furthermore, the association of greenness and fracture was greater with an increase in walkability. The HR (Q4 vs Q1) for greenness was 0.62 (95% CI, 0.46-0.82) in neighborhoods with the highest quartile of walkability.

CONCLUSIONS AND RELEVANCE

This population cohort study suggested that long-term exposure to neighborhood walkability and residential greenness were both associated with lower risk of incident fracture. The benefits of greenness increased in more walkable areas.

Long-Term Exposure to PM2.5 and Mortality: A Cohort Study in China

We investigated the association of long-term exposure to atmospheric PM2.5 with non-accidental and cause-specific mortality in Yinzhou, China. From July 2015 to January 2018, a total of 29,564 individuals aged ≥ 40 years in Yinzhou were recruited for a prospective cohort study. We used the Cox proportional-hazards model to analyze the relationship of the 2-year average concentration of PM2.5 prior to the baseline with non-accidental and cause-specific mortality. The median PM2.5 concentration was 36.51 μg/m3 (range: 25.57-45.40 μg/m3). In model 4, the hazard ratios per 10 μg/m3 increment in PM2.5 were 1.25 (95%CI: 1.04-1.50) for non-accidental mortality and 1.38 (95%CI:1.02-1.86) for cardiovascular disease mortality. We observed no associations between PM2.5 and deaths from respiratory disease or cancer. In the subgroup analysis, interactions were observed between PM2.5 and age, as well as preventive measures on hazy days. The observed association between long-term exposure to atmospheric PM2.5 at a relatively moderate concentration and the risk of non-accidental and cardiovascular disease mortality among middle-aged and elderly Chinese adults could provide evidence for government decision-makers to revise environmental policies towards a more stringent standard.

Association between air pollutants with calcaneus ultrasound T-score change in a large Taiwanese population follow-up study

Exposure to ambient air pollution has been associated with increased rates of mortality and morbidity and a shorter life expectancy. Few studies have evaluated the associations between air pollution and change in calcaneus ultrasound T-score (∆T-score). Therefore, in this longitudinal study, we explored these associations in a large group of Taiwanese participants. We used data from the Taiwan Biobank database and Taiwan Air Quality Monitoring Database, which contains detailed daily data on air pollution. We identified 27,033 participants in the Taiwan Biobank database who had both baseline and follow-up data. The median follow-up period was 4 years. The studied ambient air pollutants included particulates of 2.5 μm or less (PM_2.5), particulates of 10 μm or less (PM₁₀), ozone (O₃), carbon monoxide (CO), sulfur dioxide (SO₂), nitric oxide (NO), nitrogen dioxide (NO₂), and nitrogen oxide (NO_x). Multivariable analysis showed that PM_2.5 (β, -0.003; 95% confidence interval (CI), -0.004 to -0.001; p < 0.001), PM₁₀ (β, -0.005; 95% CI, -0.006 to -0.004, p < 0.001), O₃ (β, -0.008; 95% CI, -0.011 to -0.004; p < 0.001), and SO₂ (β, -0.036; 95% CI, -0.052 to -0.020; p < 0.001) were negatively associated with ∆T-score, and that CO (β, 0.344; 95% CI, 0.254, 0.433; p < 0.001), NO (β, 0.011; 95% CI, 0.008 to 0.015; p < 0.001), NO₂ (β, 0.011; 95% CI, 0.008 to 0.014; p < 0.001), and NO_x (β, 0.007; 95% CI, 0.005 to 0.009; p < 0.001) were positively significantly associated with ∆T-score. Furthermore, PM_2.5 and SO₂ (β, -0.014; 95% CI, -0.016 to -0.013; p < 0.001) and PM₁₀ and SO₂ (β, -0.008; 95% CI, -0.009 to -0.007; p < 0.001) had synergistic negative effects on ∆T-score. In conclusion, we found that high PM_2.5, PM₁₀, O₃, and SO₂ were associated with a rapid decline in T-score, whereas high CO, NO, NO₂, and NO_x were associated with a slow decline in T-score. Furthermore, PM_2.5 and SO₂ and PM₁₀ and SO₂ had synergistic negative effects on ∆T-score, causing an acceleration in T-score decline. These findings may be helpful when developing policies on air pollution regulation.

Outdoor air pollution exposure, bone mineral density, osteoporosis, and osteoporotic fractures: A systematic review and meta-analysis

BACKGROUND

The prevalence of osteoporosis and osteoporotic fractures is expected to increase with the aging of the population in the coming decades. In this study, we systematically reviewed the evidence on the association between exposure to air pollution and osteoporosis-related outcomes.

METHODS

We systematically searched evidence according to the PRISMA on PubMed, Scopus, and Web of Science (until August 2022). The risk of bias (RoB) was assessed using the Risk of Bias in the Non-randomized Studies of Exposures (ROBINS-E) tool. Random effects meta-analysis was applied to calculate combined estimates. We evaluated the heterogeneity using Cochran's Q test and quantified it by I² and tau² statistics. The overall body of evidence was assessed using the Grading of Recommendations Assessment, Development, and Evaluation system (GRADE) tool.

RESULTS

Out of 5254 retrieved articles, 19 studies (11 cross-sectional, seven cohorts, and one case-control) met our inclusion criteria. Most of the studies had a high probability of RoB (n = 17), and only two had a moderate RoB. Different outcomes including bone mineral density, bone mineral content, osteoporotic fracture, osteoporosis, and osteopenia were reported across the studies. The associations were reported for different air pollutants including PM2.5, PM10, nitrogen oxides, nitrogen dioxide, ozone, black carbon, carbon monoxide, sulfur dioxide, nitrogen oxide, and coarse particulate matter. Evidence was suggestive of the negative role of PM10, PM2.5, and nitrogen dioxide (e.g. bone mineral density pooled estimate: -0.02, 95%CI: -0.03: -0.01). The overall body of evidence for most of the exposure-outcome pairs was low and very low.

CONCLUSIONS

The evidence on the association between air pollution exposure and osteoporosis-related outcomes is heterogenic. However, the evidence suggests an increased risk of osteoporotic fracture and osteoporosis in outdoor air pollutants. Due to the small number of studies in each group, also observed heterogeneity, and publication bias, the results should be interpreted with caution.

Risk of ozone exposure-induced fracture

Introduction

Ozone (O3) is known to induce oxidative stress that influences various cells and tissues, which may further lead to diminished bone mineral density. Nevertheless, few studies have investigated the association between O3 exposure and fractures. Considering the similar growing trends of O3 concentrations and fracture morbidity in recent years, in the present study, we aimed to examine whether O3 exposure is associated with the fracture morbidity.

Methods

Using a retrospective cohort study design, we analyzed the records of 8,075 patients with fracture admitted in the warm season to Beijing Jishuitan Hospital from 2014 to 2019 and matched them to the corresponding exposure time and concentration of O3.

Results

The results showed that increased odds of fracture were associated with increased O3 concentrations, presumably because O3 induces oxidative stress (OS) that leads to bone mineral density (BMD) loss.

Discussion

Our findings suggest that O3 exposure is a risk factor for fractures, providing new evidence of the adverse health effect induced by air pollution. We can conclude that more intensive air pollution control is needed for the prevention of fracture occurrence.

Air pollution and decreased bone mineral density among Women's Health Initiative participants

Background

Osteoporosis heavily affects postmenopausal women and is influenced by environmental exposures. Determining the impact of criteria air pollutants and their mixtures on bone mineral density (BMD) in postmenopausal women is an urgent priority.

Methods

We conducted a prospective observational study using data from the ethnically diverse Women's Health Initiative Study (WHI) (enrollment, September 1994-December 1998; data analysis, January 2020 to August 2022). We used log-normal, ordinary kriging to estimate daily mean concentrations of PM10, NO, NO2, and SO2 at participants' geocoded addresses (1-, 3-, and 5-year averages before BMD assessments). We measured whole-body, total hip, femoral neck, and lumbar spine BMD at enrollment and follow-up (Y1, Y3, Y6) via dual-energy X-ray absorptiometry. We estimated associations using multivariable linear and linear mixed-effects models and mixture effects using Bayesian kernel machine regression (BKMR) models.

Findings

In cross-sectional and longitudinal analyses, mean PM10, NO, NO2, and SO2 averaged over 1, 3, and 5 years before the visit were negatively associated with whole-body, total hip, femoral neck, and lumbar spine BMD. For example, lumbar spine BMD decreased 0.026 (95% CI: 0.016, 0.036) g/cm2/year per a 10% increase in 3-year mean NO2 concentration. BKMR suggested that nitrogen oxides exposure was inversely associated with whole-body and lumbar spine BMD.

Interpretation

In this cohort study, higher levels of air pollutants were associated with bone damage, particularly on lumbar spine, among postmenopausal women. These findings highlight nitrogen oxides exposure as a leading contributor to bone loss in postmenopausal women, expanding previous findings of air pollution-related bone damage.

Funding

US National Institutes of Health.

IRF-1-inhibited lncRNA XIST regulated the osteogenic differentiation via miR-450b/FBXW7 axis

Osteoporosis influences life quality among elder people. Osteoblast dysfunction could cause the occurrence of osteoporosis. LncRNA XIST are involved in the progression of osteoporosis. However, the correlation between IRF-1 and XIST in osteogenic differentiation remains unclear. In the study, Clinical samples were collected for the analysis of XIST level. mRNA and protein levels were detected by RT-qPCR and western blot, respectively. H&E staining was performed to observe the histological changes in mice. Alizarin Red Staining was applied to assess the calcium deposits in hBMSCs. Meanwhile, the relation among XIST, miR-450b and FBXW7 was investigated by dual luciferase assay and ChIP. In vivo model was constructed to assess the impact of XIST in osteoporosis. XIST was found to be upregulated in osteoporosis, and XIST overexpression could inhibit the osteogenic differentiation in hBMSCs. IRF-1 could transcriptionally inhibit the expression of XIST, and XIST could inhibit osteogenic differentiation through binding with miR-450b in hBMSCs. In addition, miR-450b significantly promoted the osteogenic differentiation in hBMSCs via targeting FBXW7. Furthermore, XIST knockdown could inhibit the symptom of osteoporosis in vivo. IRF-1 promoted the osteogenic differentiation via mediation of lncRNA XIST/miR-450b/FBXW7 axis, and this finding might shed novel insights on exploring new ideas against osteoporosis.

Air pollution, genetic factors and the risk of osteoporosis: A prospective study in the UK biobank

Purpose

To reveal relationship between air pollution exposure and osteoporosis (OP) risk.

Methods

Based on large-scale data from the UK Biobank, we evaluated the relationship between OP risk and several air pollutants. Then air pollution scores (APS) were constructed to assess the combined effects of multiple air pollutants on OP risk. Finally, we constructed a genetic risk score (GRS) based on a large genome-wide association study of femoral neck bone mineral density and assessed whether single or combined exposure to air pollutants modifies the effect of genetic risk on OP and fracture risk.

Results

PM_2.5, NO₂, NO_x, and APS were significantly associated with an increased risk of OP/fracture. OP and fracture risk raised with increasing concentrations of air pollutants: compared to the lowest APS quintile group, subjects in the highest quintile group had a hazard ratio (HR) (95% CI) estimated at 1.140 (1.072-1.213) for OP and 1.080 (1.026-1.136) for fracture. Moreover, participants with low GRS and the highest air pollutant concentration had the highest risk of OP, the HRs (95% CI) of OP were 1.706 (1.483-1.964), 1.658 (1.434-1.916), 1.696 (1.478-1.947), 1.740 (1.506-2.001) and 1.659 (1.442-1.908), respectively, for PM_2.5, PM₁₀, PM_2.5-10, NO₂, and NO_x. Similar results were also observed for fractures. Finally, we assessed the joint effect of APS and GRS on the risk of OP. Participants with higher APS and lower GRS had a higher risk of developing OP. Similar results were observed in the joint effect of GRS and APS on fracture.

Conclusions

We found that exposure to air pollution, individually or jointly, could improve the risk of developing OP and fractures, and increased the risk by interacting with genetic factors.

Ambient air pollution, bone mineral density and osteoporosis: Results from a national population-based cohort study

Evidence concerning the associations of ambient air pollution exposure with bone mineral density and osteoporosis has been mixed. We conducted cross-sectional and prospective analysis of the associations between air pollution exposure and osteoporosis using data from UK Biobank study. Estimated bone mineral density (eBMD) of each participant at baseline survey was calculated using quantitative ultrasound data, and incident osteoporosis cases were identified during the follow-up period according to health-related records. Air pollution concentrations were assessed using land use regression models. We fitted multivariable linear and logistic regression models to estimate the associations of air pollution with eBMD and osteoporosis prevalence at baseline. We applied cox proportional hazard regression models to assess the relationships between air pollution and osteoporosis incidence. Among the 341,311 participants at baseline, higher air pollution exposure was associated with lower eBMD levels and increased odds of osteoporosis prevalence. For example, an IQR increase in PM_2.5, PM_2.5 absorbance, PM₁₀, NO₂ and NO_x levels were associated with 0.0018 (95% CI: 0.0012, 0.0023) to 0.0052 (95% CI: 0.0046, 0.0058) g/cm² decrease in eBMD. A total of 330,988 participants without osteoporosis were followed up for an average of 12.0 years. We identified 8105 incident osteoporosis cases (456 cases with pathological fracture and 7634 cases without pathological fracture) during the follow-up. The hazard ratios for an interquartile range increase in PM_2.5, PM_2.5 absorbance, PM₁₀, NO₂ and NO_x were 1.09 (95% CI: 1.06, 1.12), 1.04 (95% CI: 1.02, 1.07), 1.04 (95% CI: 1.01, 1.07), 1.07 (95% CI: 1.04, 1.10), and 1.06 (95% CI: 1.03, 1.09), respectively. Our study suggests that ambient air pollution might be a risk factor of decreased bone mineral density and osteoporosis incidence.

STAT3-mediated osteogenesis and osteoclastogenesis in osteoporosis

Osteoporosis is a common skeletal disease with marked bone loss, deterioration of the bone microstructure and bone fragility. An abnormal bone remodelling cycle with relatively increased bone resorption is the crucial pathophysiological mechanism. Bone remodelling is predominantly controlled by osteoblasts and osteoclasts, which are specialized cell types that are regulated by a variety of osteogenic and osteoclastic factors, including cytokines expressed within the bone microenvironment under local or systemic inflammatory conditions. Signal transducer and activator of transcription 3 (STAT3) plays a prominent role in the communication between cytokines and kinases by binding downstream gene promotors and is involved in a wide range of biological or pathological processes. Emerging evidence suggests that STAT3 and its network participate in bone remodelling and the development of osteoporosis, and this factor may be a potent target for osteoporosis treatment. This review focuses on the role and molecular mechanism of the STAT3 signalling pathway in osteogenesis, osteoclastogenesis and osteoporosis, particularly the bone-related cytokines that regulate the osteoblastic differentiation of bone marrow stromal cells and the osteoclastic differentiation of bone marrow macrophages by initiating STAT3 signalling. This review also examines the cellular interactions among immune cells, haematopoietic cells and osteoblastic/osteoclastic cells.