Relationship Between Pulmonary Emphysema and Osteoporosis Assessed by CT in Patients With COPD

Tadashi Ohara, MD; Toyohiro Hirai, MD, PhD; Shigeo Muro, MD, PhD; Akane Haruna, MD; Kunihiko Terada, MD; Daisuke Kinose, MD; Satoshi Marumo, MD; Emiko Ogawa, MD, PhD; Yuma Hoshino, MD, PhD; Akio Niimi, MD, PhD; Kazuo Chin, MD, PhD; Michiaki Mishima, MD, PhD

Disclosures

CHEST. 2008;134(6):1244-1249. 

In This Article

Abstract and Introduction

Abstract

Background: Osteoporosis is one of the important systemic features of COPD. Although COPD itself is regarded as one risk factor for osteoporosis, the relationship between the extent of emphysema and reduced bone density is still unclear. Our first aim was therefore to measure vertebral bone density and the percentage of low-attenuation area (LAA%) in the lungs using chest CT scans in COPD patients. Our second aim was to investigate the relationships among CT scan measurements, anthropometric parameters, and pulmonary function.
Methods: Chest CT scans and pulmonary function tests were performed in 65 male patients with COPD. Using CT images, the CT scan density of the thoracic and lumbar vertebrae (T4, T7, T10, and L1) and the LAA% were measured quantitatively, and their correlations were analyzed.
Results: Linear regression analyses revealed that LAA% had a significant negative correlation with bone mineral density (BMD) [r = -0.522]. In addition, multiple regression analysis showed that only LAA% and body mass index (BMI) were predictive of BMD among age, BMI, smoking index, FEV1, arterial blood gas, and LAA%.
Conclusions: The extent of pulmonary emphysema significantly correlated with reduced bone density. Our study suggested that COPD itself could be a risk factor for osteoporosis and that chest CT scanning is useful for the management of COPD as a systemic disease.

Introduction

COPD not only involves the lungs but also causes extrapulmonary abnormalities with systemic features, such as, for example, cachexia, skeletal muscle wasting, and anemia.[1] Osteoporosis is also an important systemic feature of COPD. Osteoporotic fractures cause many symptoms and complications, including the impairment of ventilation,[2] and create a heavy economic burden.[3] To predict the risk of osteoporotic fractures, measurements of bone mineral density (BMD) have been widely used,[4,5,6,7] and it has been reported[8,9,10] that BMD is lower in COPD patients than in healthy subjects. Thus, it is important to evaluate BMD in the management of COPD.

BMD can be measured by several noninvasive procedures, such as dual x-ray absorptiometry,[7,8,9,11,12,13,14,15] quantitative CT scanning,[16,17,18,19,20] and quantitative ultrasound.[12] It has been reported that CT scan density in vertebra exhibited a highly significant positive correlation with pathologic measurements of vertebral bone density[4] and that measurements of vertebral density by CT scan were better than those obtained by dual x-ray absorptiometry to predict vertebral fractures.[7] In addition, chest CT scanning has been widely used to assess pulmonary emphysema quantitatively.[21] Thus, chest CT scanning that is performed to diagnose and evaluate pulmonary emphysema can be simultaneously used to evaluate bone density in vertebrae without additional radiation exposure. However, the relationship between the extent of emphysema evaluated quantitatively and the loss of bone density in patients with COPD has not been reported. Therefore, our first aim was to measure both CT scan density in the vertebral bones and the low-attenuation area (LAA) in the lungs using chest CT images. The second aim was to investigate the relationship between emphysema and osteoporosis using quantitative CT scan parameters.

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