Does radiographic emphysema correlate with low bone mineral density?

Quantitative Vertebral Bone Density Seen on Chest CT in Chronic Obstructive Pulmonary Disease Patients: Association with Mortality in the Korean Obstructive Lung Disease Cohort

Objective

Patients with chronic obstructive pulmonary disease (COPD) are known to be at risk of osteoporosis. The purpose of this study was to evaluate the association between thoracic vertebral bone density measured on chest CT (D_Thorax) and clinical variables, including survival, in patients with COPD.

Materials and Methods

A total of 322 patients with COPD were selected from the Korean Obstructive Lung Disease (KOLD) cohort. D_Thorax was measured by averaging the CT values of three consecutive vertebral bodies at the level of the left main coronary artery with a round region of interest as large as possible within the anterior column of each vertebral body using an in-house software. Associations between D_Thorax and clinical variables, including survival, pulmonary function test (PFT) results, and CT densitometry, were evaluated.

Results

The median follow-up time was 7.3 years (range: 0.1–12.4 years). Fifty-six patients (17.4%) died. D_Throax differed significantly between the different Global Initiative for Chronic Obstructive Lung Disease stages. D_Throax correlated positively with body mass index (BMI), some PFT results, and the six-minute walk distance, and correlated negatively with the emphysema index (EI) (all p < 0.05). In the univariate Cox analysis, older age (hazard ratio [HR], 3.617; 95% confidence interval [CI], 2.119–6.173, p < 0.001), lower BMI (HR, 3.589; 95% CI, 2.122–6.071, p < 0.001), lower forced expiratory volume in one second (FEV₁) (HR, 2.975; 95% CI, 1.682–5.262, p < 0.001), lower diffusing capacity of the lung for carbon monoxide corrected with hemoglobin (DL_CO) (HR, 4.595; 95% CI, 2.665–7.924, p < 0.001), higher EI (HR, 3.722; 95% CI, 2.192–6.319, p < 0.001), presence of vertebral fractures (HR, 2.062; 95% CI, 1.154–3.683, p = 0.015), and lower D_Thorax (HR, 2.773; 95% CI, 1.620–4.746, p < 0.001) were significantly associated with all-cause mortality and lung-related mortality. In the multivariate Cox analysis, lower D_Thorax (HR, 1.957; 95% CI, 1.075–3.563, p = 0.028) along with older age, lower BMI, lower FEV₁, and lower DL_CO were independent predictors of all-cause mortality.

Conclusion

The thoracic vertebral bone density measured on chest CT demonstrated significant associations with the patients' mortality and clinical variables of disease severity in the COPD patients included in KOLD cohort.

Relationship of annual change in bone mineral density with extent of emphysematous lesions and pulmonary function in patients with COPD

Background

Osteoporosis is a well-known comorbidity in COPD. It is associated with poor health status and prognosis. Although the exact pathomechanisms are unclear, osteoporosis is suggested to be either a comorbidity due to shared risk factors with COPD or a systematic effect of COPD with a cause-effect relationship. This study aimed to evaluate whether progression of osteoporosis is synchronized with that of COPD.

Materials and methods

Data from 103 patients with COPD included in the Hokkaido COPD cohort study were analyzed. Computed tomography (CT) attenuation values of thoracic vertebrae 4, 7, and 10 were measured using custom software, and the average value (average bone density; ABD_4,7,10) was calculated. The percentage of low attenuation volume (LAV%) for each patient was also calculated for evaluation of emphysematous lesions. Annual change in thoracic vertebral CT attenuation, which is strongly correlated with dual-energy X-ray absorptiometry-measured bone mineral density, was compared with that in FEV_1.0 or emphysematous lesions.

Results

In the first CT data set, ABD_4,7,10 was significantly correlated with age (ρ=-0.331; p=0.0006), body mass index (BMI; ρ=0.246; p=0.0136), St George's Respiratory Questionnaire (SGRQ) activity score (ρ=-0.248; p=0.0115), eosinophil count (ρ=0.229; p=0.0198), and LAV% (ρ=-0.372; p=0.0001). However, ABD_4,7,10 was not associated with FEV_1.0. After adjustment for age, BMI, SGRQ activity score, and eosinophil count, no significant relationship was found between ABD_4,7,10 and LAV%. Annual change in ABD_4,7,10 was not associated with annual change in LAV% or FEV_1.0.

Conclusion

Progression of osteoporosis and that of COPD are not directly related or synchronized with each other.

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

BACKGROUND

Osteoporosis, the most common extra-pulmonary complication of chronic obstructive pulmonary disease (COPD), may be related to general causes or COPD-specific causes such as low forced expiratory volume in 1 s (FEV1) and hypoxia. A few studies reported that emphysema is an independent risk factor for osteoporosis. However, other workers considered the association to be confounded by low FEV1 and low body mass index (BMI) which cluster with emphysema.

AIMS

To study the association between osteoporosis and emphysema in a model that includes these potentially confounding factors.

METHODS

We studied prospectively 52 COPD patients with both high resolution computed tomography and carbon monoxide diffusion coefficient as diagnostic markers of emphysema. Dual-energy X-ray absorptiometry was used to measure the bone mass density (BMD) of lumbar vertebrae and neck of the femur. Vertebral fractures were evaluated using the Genant semiquantitative score. Multiple linear regression analysis was used to identify the following independent variables: age, BMI, FEV1% predicted, PaO2, emphysema score, C-reactive protein (CRP), and dyspnea score as related to BMD. P ≤ 0.05 was considered statistically significant.

RESULTS

There was no significant difference in the serum Vitamin D levels, vertebral fracture score, or BMD between the emphysematous and nonemphysematous patients. Multivariate analysis showed that (in a model including age, BMI, FEV1, PaO2, emphysema score, CRP, and dyspnea score) only reduced BMI, FEV1, and PaO2 were independent risk factors for low BMD.

CONCLUSIONS

The emphysematous phenotype is not a risk factor for osteoporosis independently of BMI, FEV1, and PaO2.

Idiopathic pulmonary fibrosis a rare disease with severe bone fragility

Idiopathic pulmonary fibrosis (IPF) is a rare form of chronic, progressive fibrosing interstitial pneumonia of unknown cause. The aim of this cross-sectional study was to assess the prevalence of osteoporosis and fragility fracture in a population of adults with IPF and to identify whether any possible clinical and pulmonary function parameters may be associated with increased bone fragility. In 58 IPF patients (mean age 65.1 ± 9.1 years), we measured bone mineral density (BMD) of the lumbar spine, the femoral neck, and the entire hip. Moreover, the presence of vertebral fractures on a lateral chest X-ray study was evaluated, and a vertebral fracture burden was quantified using the spinal deformity index (SDI). As expected, osteoporosis was significantly more frequent in females with respect to males (57.9 vs 20.5 %, respectively), whereas the fractures prevailed in males with respect to females (38.5 vs 26.3 %, respectively). There were positive correlations between BMD at all skeletal sites and respiratory parameters; in particular for FVC % and DLCO % with BMD at femoral sub-regions. Moreover, we compared the average of DLCO (%) measure by values of SDI score that was higher in those patients with lower values of DLCO (%). The study shows a high prevalence of fragility with vertebral fractures in IPF patients, especially in males. Moreover, the vertebral fracture burden is associated with a worsening of FVC (%) and DLCO (%). Therefore, an evaluation of bone status is recommended, especially in those patients who are candidates for lung transplantation.

Fracture prevention in COPD patients; a clinical 5-step approach

Although osteoporosis and its related fractures are common in patients with COPD, patients at high risk of fracture are poorly identified, and consequently, undertreated. Since there are no fracture prevention guidelines available that focus on COPD patients, we developed a clinical approach to improve the identification and treatment of COPD patients at high risk of fracture. We organised a round-table discussion with 8 clinical experts in the field of COPD and fracture prevention in the Netherlands in December 2013. The clinical experts presented a review of the literature on COPD, osteoporosis and fracture prevention. Based on the Dutch fracture prevention guideline, they developed a 5-step clinical approach for fracture prevention in COPD. Thereby, they took into account both classical risk factors for fracture (low body mass index, older age, personal and family history of fracture, immobility, smoking, alcohol intake, use of glucocorticoids and increased fall risk) and COPD-specific risk factors for fracture (severe airflow obstruction, pulmonary exacerbations and oxygen therapy). Severe COPD (defined as postbronchodilator FEV₁ < 50% predicted) was added as COPD-specific risk factor to the list of classical risk factors for fracture. The 5-step clinical approach starts with case finding using clinical risk factors, followed by risk evaluation (dual energy X-ray absorptiometry and imaging of the spine), differential diagnosis, treatment and follow-up. This systematic clinical approach, which is evidence-based and easy-to-use in daily practice by pulmonologists, should contribute to optimise fracture prevention in COPD patients at high risk of fracture.

Relationship between femur neck bone mineral density and prevalent chronic obstructive pulmonary disease (COPD) or COPD mortality in older non-Hispanic white adults from NHANES III

SUMMARY

The relationship between femur neck bone mineral density (FNBMD), prevalent COPD, and COPD mortality was examined in older non-Hispanic white adults from NHANES III. FNBMD was significantly related to prevalent COPD and COPD mortality before and after adjusting for shared risk factors.

INTRODUCTION

Bone mineral density (BMD) has been linked to chronic obstructive pulmonary disease (COPD), but little is known about its relationship with COPD mortality. The present study examined the relationship between FNBMD, prevalent COPD, and COPD mortality in older non-Hispanic white adults from the third National Health and Nutrition Examination Survey (NHANES III, 1988-1994).

METHODS

COPD status at baseline was defined by self-reported physician's diagnosis and by airway obstruction based on spirometry measurements in 3,275 non-Hispanic whites aged 50 years and older. COPD mortality cases were identified using linked mortality records obtained through 2006. FNBMD was measured by dual-energy x-ray absorptiometry. Multiple regression was used to examine the baseline relationship between COPD and FNBMD. Cox proportional hazards models were used to estimate the hazards ratio (HR) for COPD mortality by FNBMD.

RESULTS

Twelve percent self-reported a physician's diagnosis of COPD, 23 % had mild or moderate airway obstruction, and 9 % had severe or very severe airway obstruction. There were 180 COPD mortality cases in the sample. FNBMD was significantly lower in those with self-reported COPD diagnosis or airway obstruction before and after adjusting for shared risk factors (p < 0.05). COPD mortality risk was significantly increased for each standard deviation decline in FNBMD before (by 68 %) and after (by 26-38 %) adjusting for shared risk factors.

CONCLUSIONS

Low FNBMD was associated with both baseline COPD and future COPD mortality. Shared risk factors appeared to explain some, but not all, of these relationships.

Associations between COPD related manifestations: a cross-sectional study

Background

Cardiovascular disease, osteoporosis and emphysema are associated with COPD. Associations between these factors and whether they predict all-cause mortality in COPD patients are not well understood. Therefore, we examined associations between markers of cardiovascular disease (coronary artery calcification [CAC], thoracic aortic calcification [TAC] and arterial stiffness), bone density (bone attenuation of the thoracic vertebrae), emphysema (PI-950 and 15th percentile) and all-cause mortality in a COPD cohort.

Methods

We assessed CAC, TAC, bone attenuation of the thoracic vertebrae, PI-950 and 15th percentile on low-dose chest computed tomography in COPD subjects. We measured arterial stiffness as carotid-radial pulse wave velocity (PWV), and identified deaths from the national register.

Results

We studied 119 COPD subjects; aged 67.8 ±7.3, 66% were males and mean FEV₁% predicted was 46.0 ±17.5. Subjects were classified into three pre-specificed groups: CAC = 0 (n = 14), 0 < CAC ≤ 400 (n = 41) and CAC > 400 (n = 64). Subjects with higher CAC were more likely to be older (p < 0.001) and male (p = 0.03), and more likely to have higher systolic blood pressure (p = 0.001) and a history of hypertension (p = 0.002) or ischemic heart disease (p = 0.003). Higher CAC was associated with higher PWV (OR 1.62, p = 0.04) and lower bone attenuation (OR 0.32, p = 0.02), but not with 15th percentile, after adjustment for age, sex and pack-years of smoking. In a Cox proportional hazards model, CAC, TAC and 15th percentile predicted all-cause mortality (HR 2.01, 2.09 and 0.66, respectively).

Conclusions

Increased CAC was associated with increased arterial stiffness and lower bone density in a COPD cohort. In addition, CAC, TAC and extent of emphysema predicted all-cause mortality.

Trial registration

Lothian NHS Board, Lothian Research Ethics Committee, LREC/2003/8/28.

Bone stiffness and failure load are related with clinical parameters in men with chronic obstructive pulmonary disease

Osteoporosis is frequently seen in patients with chronic obstructive pulmonary disease (COPD). Because research on bone structure and bone strength in COPD patients is limited, the objectives of this pilot study were as follows: (1) to compare bone structure, stiffness, and failure load, measured at the peripheral skeleton, between men with and without COPD after stratification for areal bone mineral density (aBMD); and (2) to relate clinical parameters with bone stiffness and failure load in men with COPD. We included 30 men with COPD (normal aBMD, n = 18; osteoporosis, n = 12) and 17 men without COPD (normal aBMD, n = 9; osteoporosis, n = 8). We assessed pack-years of smoking, body mass index (BMI), fat free mass index (FFMI), pulmonary function (forced expiratory volume in 1 second [FEV1 ], FEV1 /forced vital capacity [FVC], diffusion capacity for carbon monoxide [DLCO], and transfer coefficient for carbon monoxide [KCO]), and extent of emphysema. Bone structure of the distal radius and tibia was assessed by high-resolution peripheral quantitative computed tomography (HR-pQCT), and bone stiffness and failure load of the distal radius and tibia were estimated from micro finite element analysis (µFEA). After stratification for aBMD and COPD, men with osteoporosis showed abnormal bone structure (p < 0.01), lower bone stiffness (p < 0.01), and lower failure load (p < 0.01) compared with men with normal aBMD, and men with COPD had comparable bone structure, stiffness, and failure load compared with men without COPD. In men with COPD, lower FFMI was related with lower bone stiffness, and failure load of the radius and tibia and lower DLCO and KCO were related with lower bone stiffness and failure load of the tibia after normalization with respect to femoral neck aBMD. Thus, this pilot study could not detect differences in bone structure, stiffness, and failure load between men with and without COPD after stratification for aBMD. FFMI and gas transfer capacity of the lung were significantly related with bone stiffness and failure load in men with COPD after normalization with respect to femoral neck aBMD.

Osteoporosis in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is being regarded as a heterogeneous disease with clinically significant pulmonary and extrapulmonary manifestations, such as emphysema, cardiovascular disease and osteoporosis. Osteoporosis is characterized by low bone mass and microarchitectural deterioration of bone tissue, leading to enhanced bone fragility and, consequently, an increased risk of fracture. Fractures resulting from osteoporosis might contribute to increased morbidity and mortality, particularly in COPD patients. The high prevalence of osteoporosis in COPD patients is assumed to be due to common risk factors, such as older age and tobacco smoking, and COPD-specific risk factors, such as systemic inflammation, vitamin D deficiency and the use of oral or inhaled corticosteroids. This review provides a state-of-the-art summary of the prevalence, pathophysiology, diagnosis, risk factors and treatment of osteoporosis in COPD patients. It also discusses potential mechanisms linking COPD with osteoporosis.

CT-measured bone attenuation in patients with chronic obstructive pulmonary disease: relation to clinical features and outcomes

Osteoporosis is highly prevalent in chronic obstructive pulmonary disease (COPD) patients and has been related to several clinical features. However, most studies have been in relatively small COPD cohorts. Therefore, the objectives of this study were to compare bone attenuation measured on low-dose chest computed tomography (CT) between COPD subjects and smoker and nonsmoker controls, and to relate bone attenuation to clinical parameters, inflammatory biomarkers, and outcomes in a large, well-characterized COPD cohort. We studied 1634 COPD subjects, 259 smoker controls, and 186 nonsmoker controls who participated in a large longitudinal study (ECLIPSE). We measured bone attenuation, extent of emphysema, and coronary artery calcification (Agatston score) on baseline CT scans, and clinical parameters, inflammatory biomarkers, and outcomes. Bone attenuation was lower in COPD subjects compared with smoker and nonsmoker controls (164.9 ± 49.5 Hounsfield units [HU] versus 183.8 ± 46.1 HU versus 212.1 ± 54.4 HU, p < 0.001). Bone attenuation was not significantly different between COPD subjects and smoker controls after adjustment for age, sex, and pack-years of smoking. In the COPD subjects, bone attenuation correlated positively with forced expiratory volume in 1 second (FEV₁, r = 0.062, p = 0.014), FEV₁/forced vital capacity (FVC) ratio (r = 0.102, p < 0.001), body mass index (r = 0.243, p < 0.001), fat-free mass index (FFMI, r = 0.265, p < 0.001), and C-reactive protein (r = 0.104, p < 0.001), and correlated negatively with extent of emphysema (r = -0.090, p < 0.001), Agatston score (r = -0.177, p < 0.001), and interleukin-8 (r = -0.054, p = 0.035). In a multiple regression model, older age, lower FFMI and higher Agatston score were associated with lower bone attenuation. Lower bone attenuation was associated with higher exacerbation (r = -0.057, p = 0.022) and hospitalization (r = -0.078, p = 0.002) rates but was not associated with all-cause mortality. In conclusion, CT-measured bone attenuation was lower in COPD subjects compared with nonsmoker controls but not compared with smoker controls, after adjustment for age, sex, and pack-years of smoking. In the COPD subjects, bone attenuation was associated with age, body composition, and coronary artery calcification but was not associated with all-cause mortality.