Abstract
ABSTRACTGreater kyphosis angles lead to increased loading on vertebral bodies in computational models. However, results about the relationship between severity of kyphosis and incident vertebral fracture (VF) risk have been conflicting. Therefore, the aim of this study was to evaluate associations between 1) prevalent VFs and severity of kyphosis, and 2) severity of kyphosis and incident VF risk in smokers with or without chronic obstructive pulmonary disease (COPD). Former and current smokers with or without COPD were included. CT scans were made at baseline, 1‐year, and 3‐year follow‐up. VFs were evaluated on superposed sagittal CT reconstructions. Kyphosis was measured as the angle between the lines above T4 and below T9 or T12. We included 1239 subjects (mean age 61.3 ± 8.0 years, 61.1% male, 80.6% with COPD), of whom 253 (20.4%) had a prevalent VF and 294 (23.7%) an incident VF within 3 years. Presence, number, and severity of prevalent VFs were associated with a greater kyphosis angle. The mean increase in kyphosis angle within 3 years was small but significantly greater in subjects with incident VFs compared with those without (2.2 ± 4.1 versus 1.2 ± 3.9 degrees, respectively, for T4 to T12 angle, p < 0.001). After adjustment for bone attenuation (BA) and prevalent VFs, baseline kyphosis angle was associated with incident VFs within 1 and 3 years (angle T4 to T12 per +1 SD, hazard ratio [HR] = 1.34 [1.12–1.61] and HR 1.29 [1.15–1.45], respectively). Our data showed that a greater kyphosis angle at baseline was independently associated with increased risk of incident VFs within 1 and 3 years, supporting the theory that greater kyphosis angle contributes to higher biomechanical loads in the spine. © 2019 American Society for Bone and Mineral Research.
Highlights
Chronic obstructive pulmonary disease (COPD) is caused by significant exposure to noxious particles and gases, most often tobacco smoking and exposure to air pollution.[1,2,3,4] It is characterized by chronic airflow limitation that is caused by a mixture of small airways disease and parenchymal destruction
COPD is primarily a pulmonary disease, there are significant comorbidities and extrapulmonary effects, such as cardiovascular disease, diabetes, muscle wasting, and osteoporosis.[5,6,7,8] The reported prevalence of vertebral fractures (VFs) is high among patients with COPD (9% to 79%),(9–18) and we have recently shown that incident VF risk is high in COPD patients and smokers without COPD with one or more prevalent VFs.[19]
Roux and colleagues assessed 1624 subjects from the Spinal Osteoporosis Therapeutic Intervention (SOTI) and Treatment of Peripheral Osteoporosis (TROPOS) studies, and found relative risks (RRs) of 1.30 (1.00–1.68) and 1.42 (1.08–1.86) when the highest T4 to T12 angle tertile was compared with the medium and to the lowest tertile, respectively, after adjustment for age, body mass index (BMI), spine bone mineral density (BMD), and prevalent VFs.[29]. In contrast, Katzman and colleagues assessed 3038 women with low BMD from the Fracture Intervention Trial and did not find a significant influence of increased C7 to T12 kyphosis angle on incident VF risk after adjustment for prevalent VFs.[30]
Summary
Chronic obstructive pulmonary disease (COPD) is caused by significant exposure to noxious particles and gases, most often tobacco smoking and exposure to air pollution.[1,2,3,4] It is characterized by chronic airflow limitation that is caused by a mixture of small airways disease (eg, obstructive bronchiolitis) and parenchymal destruction (emphysema). Roux and colleagues assessed 1624 subjects from the Spinal Osteoporosis Therapeutic Intervention (SOTI) and Treatment of Peripheral Osteoporosis (TROPOS) studies, and found relative risks (RRs) of 1.30 (1.00–1.68) and 1.42 (1.08–1.86) when the highest T4 to T12 angle tertile was compared with the medium and to the lowest tertile, respectively, after adjustment for age, body mass index (BMI), spine bone mineral density (BMD), and prevalent VFs.[29] In contrast, Katzman and colleagues assessed 3038 women with low BMD from the Fracture Intervention Trial and did not find a significant influence of increased C7 to T12 kyphosis angle on incident VF risk after adjustment for prevalent VFs.[30]. Our aim was to evaluate the associations between 1) prevalent VFs and thoracic kyphosis angle, and 2) between thoracic kyphosis angle and incident VFs in current and former smokers with or without COPD
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