A study of chronic obstructive pulmonary disease-specific causes of osteoporosis with emphasis on the emphysema phenotype

Chronic Obstructive Pulmonary Disease and Osteoporosis: A Two-Sample Mendelian Randomization Analysis

Background

There is a global increase in the prevalence of osteoporosis and chronic obstructive pulmonary disease (COPD). Studies based on observation revealed a higher incidence of osteoporosis in patients with COPD. We looked into the genetic relationship between COPD and osteoporosis using the Mendelian randomization (MR) technique.

Methods

The inverse variance-weighted (IVW) method was the primary technique used in this MR investigation. The sensitivity was assessed using the simple median, weighted median, penalized weighted median, and MR Egger regression analysis.

Results

The IVW model demonstrated that genetically determined COPD is causally associated with an elevated risk of osteoporosis (odds ratio [OR] fixed-effect, 1.010; 95% confidence interval [CI], 1.001-1.019, P=0.021; OR random-effect, 1.010; 95% CI, 1.001-1.020, P=0.039). It was also found that this correlation held valid for the simple and weighted median, Penalized weighted, MR-Egger, and MR Egger (bootstrap) approaches. No heterogeneity was found in the IVW or MR-Egger analysis results (Q=131.374, P=0.061 and Q=128.895, P=0.069, respectively). Furthermore, no pleiotropic influence via genetic variations was revealed by MR-Egger regression (intercept, -0.0002; P=0.160). No one single nucleotide polymorphism was found to have a substantial impact on the relationship between COPD and osteoporosis by the leave-one-out sensitivity analysis.

Conclusion

Our MR analysis demonstrated a substantial positive impact of COPD on the risk of osteoporosis.

Lung Function Impairment, Associating Hyperinflation with Impaired Diffusion Capacity and Transfer Coefficient, Is a Risk Factor for Hip Osteoporosis in Patients with Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is a risk factor for osteoporosis. Our objective is to determine if functional indices associated with emphysema on pulmonary function tests (DLCO—diffusion capacity of the lung for CO-; DLCO/AV—DLCO corrected for alveolar volume- and TLC—total lung capacity), considered alone or together, can identify COPD patients with osteoporosis. Methods: 90 COPD patients underwent dual-energy X-ray absorptiometry (DEXA) and pulmonary function tests. Results: 26% of the COPD patients were osteoporotic. In univariate analysis, each functional parameter associated with emphysema, analyzed separately, was not associated with osteoporosis. In contrast, patients with hyperinflation associated with impaired diffusion capacity and transfer coefficient, defined by the association of the three functional indices (DLCO < 70%, DLCO/AV < 80% and CPT > 115%), had significantly more osteoporosis at the total hip (OR: 5.9, CI: 1.5–23.8, p = 0.013). In multivariate analysis, this phenotype was confirmed as an independent factor associated with hip osteoporosis. In contrast, COPD airway obstruction severity, based on FEV1 (%), was not associated with osteoporosis. A lower BMI, female gender and age were also identified as osteoporosis risk factors. Conclusions: COPD patients with hyperinflation associated with impaired diffusion capacity and transfer coefficient are at higher risk for osteoporosis. Pulmonary function tests associated with emphysema detection can help to identify COPD patients with osteoporosis, in addition to the classical risk factors.

Osteoporosis in Patients With Respiratory Diseases

Climate change, environmental pollution, and virus epidemics have sharply increased the number of patients suffering from respiratory diseases in recent years. Prolonged periods of illness and drug use increase the occurrence of complications in these patients. Osteoporosis is the common bone metabolism disease with respiratory disturbance, which affects prognosis and increases mortality of patients. The problem of osteoporosis in patients with respiratory diseases needs more attention. In this review, we concluded the characteristics of osteoporosis in some respiratory diseases including COPD, asthma, COVID-19, tuberculosis, and lung cancer. We revealed that hypoxia was the common pathogenesis of osteoporosis secondary to respiratory diseases, with malnutrition and corticosteroid abuse driving the progression of osteoporosis. Hypoxia-induced ROS accumulation and activated HIF-1α lead to attenuated osteogenesis and enhanced osteoclastogenesis in patients with respiratory diseases. Tuberculosis and cancer also invaded bone tissue and reduced bone strength by direct infiltration. For the treatment of osteoporosis in respiratory patients, oral-optimized bisphosphonates were the best treatment modality. Vitamin D was a necessary supplement, both for calcium absorption in osteogenesis and for improvement of respiratory lesions. Reasonable adjustment of the dose and course of corticosteroids according to the etiology and condition of patients is beneficial to prevent the occurrence and development of osteoporosis. Additionally, HIF-1α was a potential target for the treatment of osteoporosis in respiratory patients, which could be activated under hypoxia condition and involved in the process of bone remodeling.

Imbalance Between Injury and Defense in the COPD Emphysematous Phenotype

The chronic obstructive pulmonary disease (COPD) emphysematous phenotype is characterized by destruction of lung tissue structure. Patients with this phenotype usually present with typical emphysema-like changes on chest computed Tomography CT, experience higher mortality and poorer prognosis, and are insensitive to routine pharmacological COPD therapy. However, the pathogenesis for the COPD emphysematous phenotype remains unclear, resulting in diagnostic and therapeutic challenges. The imbalance between injury and defense mechanisms is essential in the progression of many pulmonary diseases. Thus, in this review, we focus on the pathogenesis of the COPD emphysematous phenotype and discuss the pathophysiological processes involved in disease progression, from the perspective of injury and defense imbalance.

COPD phenotypes and machine learning cluster analysis: A systematic review and future research agenda

Chronic Obstructive Pulmonary Disease (COPD) is a highly heterogeneous condition projected to become the third leading cause of death worldwide by 2030. To better characterize this condition, clinicians have classified patients sharing certain symptomatic characteristics, such as symptom intensity and history of exacerbations, into distinct phenotypes. In recent years, the growing use of machine learning algorithms, and cluster analysis in particular, has promised to advance this classification through the integration of additional patient characteristics, including comorbidities, biomarkers, and genomic information. This combination would allow researchers to more reliably identify new COPD phenotypes, as well as better characterize existing ones, with the aim of improving diagnosis and developing novel treatments. Here, we systematically review the last decade of research progress, which uses cluster analysis to identify COPD phenotypes. Collectively, we provide a systematized account of the extant evidence, describe the strengths and weaknesses of the main methods used, identify gaps in the literature, and suggest recommendations for future research.

Prevalence and Risk Factors for Osteoporosis in Individuals With COPD: A Systematic Review and Meta-analysis

BACKGROUND

Osteoporosis is prevalent in individuals with COPD. Updated evidence is required to complement the previous systematic review on this topic to provide best practice. The aim of this systematic review and meta-analysis was to quantitatively synthesize data from studies with respect to the prevalence and risk factors for osteoporosis among individuals with COPD.

METHODS

EMBASE, CINAHL, MEDLINE, and PubMed databases were searched for articles containing the key words "COPD," "osteoporosis," "prevalence," and "risk factor." Eligibility screening, data extraction, and quality assessment of the retrieved articles were conducted independently by two reviewers. Meta-analyses were performed to determine osteoporosis prevalence and risk factors in individuals with COPD. Meta-regression analyses were conducted to explore the sources of heterogeneity.

RESULTS

The pooled global prevalence from 58 studies was 38% (95% CI, 34-43). The presence of COPD increased the likelihood of having osteoporosis (OR, 2.83). Other significant risk factors for osteoporosis in COPD patients were BMI < 18.5 kg/m² (OR, 4.26) and the presence of sarcopenia (OR, 3.65).

CONCLUSIONS

Osteoporosis is prevalent in individuals with COPD, and the prevalence seems to be high and similar in many countries. Patients with COPD should be screened for osteoporosis and contributing risk factors.

Bone mineral density and vertebral fractures and their relationship with pulmonary dysfunction in patients with chronic obstructive pulmonary disease

To evaluate bone mineral density (BMD) and morphometric vertebral fractures (MVF) in chronic obstructive pulmonary disease (COPD) patients in comparison with two control groups. BMD was lower in the disease group (DG) and was associated with the worst disease severity and prognosis. The prevalence of MVF was high and greater in the DG than in the control groups.

INTRODUCTION

Chronic obstructive pulmonary disease (COPD) is associated with osteoporosis and vertebral fractures. It is still unclear whether the presence of fractures and changes in bone mineral density (BMD) are associated with disease severity and prognosis. The aim of this study was to evaluate BMD and morphometric vertebral fractures (MVF) in COPD patients in comparison with two control groups and to correlate these parameters with indices of COPD severity (VEF1 and GOLD) and prognosis (BODE).

METHODS

This was a cross-sectional study in COPD patients (disease group, DG) who underwent BMD and vertebral fracture assessment (VFA). Two control groups were used: smokers without COPD (smoker group, SG) and healthy never-smoker individuals (never-smoker group, NSG).

RESULTS

The DG comprised 121 patients (65 women, mean age 67.9 ± 8.6 years). Altered BMD was observed in 88.4% of the patients in the DG, which was more prevalent when compared with the control groups (p < 0.001). The BMD values were lower in the DG than in the control groups (p < 0.05). BMD was associated with the worst disease severity and prognosis (p < 0.05). The prevalence of MVF was high (57.8%) and greater than that in the SG (23.8%) and the NSG (14.8%; p < 0.001). The prevalence of fractures was not associated with disease severity and prognosis.

CONCLUSIONS

COPD patients have a higher prevalence of MVF and low BMD, and the latter was associated with the severity and poor prognosis of the disease.

Increased rate of osteoporosis, low lean mass, and fragility fractures in COPD patients: association with disease severity

A very high rate of osteoporosis, fractures, and low lean mass was observed in patients with chronic obstructive pulmonary disease (COPD). Disease severity was associated with bone and muscle adverse outcomes, while age ≥ 63.5 years old, low lean mass, higher iPTH, and a T-score below - 2.5 were all associated with higher risk of fracture.

INTRODUCTION

Osteoporosis is frequently neglected in patients with COPD. We aimed at evaluating the rate of osteoporosis, fractures, and low lean mass in patients with COPD.

METHODS

Ninety-nine patients with COPD (53 women, 64.5 ± 9.6 years old, and 46 men, 65.9 ± 8.0 years old) underwent bone densitometry (DXA) with body composition analyses. Healthy individuals (N = 57) not exposed to tobacco matched by sex, age, and body mass index (BMI) were used as controls. Spirometry, routine laboratory workout, and conventional thoracolumbar radiography surveying for vertebral deformities were performed in all patients.

RESULTS

Osteoporosis was found in 40.4% of the COPD patients against only 13.0% of the healthy controls (p = 0.001). Vertebral fractures were seen in 24.4% of the men and 22.0% of the women with COPD. Disease severity (GOLD 3 and 4) was significantly associated with higher risk of vitamin D deficiency (p = 0.032), lower BMD (both men and women at all sites), higher frequency of osteoporosis (in women at all sites), lower skeletal mass index, and higher rate of low lean mass (in both men and women) than healthy controls and COPD patients with milder disease (GOLD 1 and 2). Age was a main predictor of vertebral fractures (OR = 1.164 (1.078-9.297); p < 0.001), while high plasma iPTH (OR = 1.045 (1.005-1.088); p = 0.029) and low ALM (OR = 0.99965 (0.99933-0.99997); p = 0.031) were predictors of non-vertebral fractures.

CONCLUSION

Highly prevalent in COPD, osteoporosis and low lean mass were associated with FEV_1% < 50%. Age, low lean mass, high iPTH, and low bone mass were all significantly associated with fractures in COPD patients.

Metabolic Disorders in Chronic Lung Diseases

Chronic lung diseases represent complex diseases with gradually increasing incidence, characterized by significant medical and financial burden for both patients and relatives. Their increasing incidence and complexity render a comprehensive, multidisciplinary, and personalized approach critically important. This approach includes the assessment of comorbid conditions including metabolic dysfunctions. Several lines of evidence show that metabolic comorbidities, including diabetes mellitus, dyslipidemia, osteoporosis, vitamin D deficiency, and thyroid dysfunction have a significant impact on symptoms, quality of life, management, economic burden, and disease mortality. Most recently, novel pathogenetic pathways and potential therapeutic targets have been identified through large-scale studies of metabolites, called metabolomics. This review article aims to summarize the current state of knowledge on the prevalence of metabolic comorbidities in chronic lung diseases, highlight their impact on disease clinical course, delineate mechanistic links, and report future perspectives on the role of metabolites as disease modifiers and therapeutic targets.