Low bone mineral density in COPD patients with osteoporosis is related to low daily physical activity and high COPD assessment test scores

Abstract

COPD patients have an increased prevalence of osteoporosis (OP) compared with healthy people. Physical inactivity in COPD patients is a crucial risk factor for OP; the COPD assessment test (CAT) is the newest assessment tool for the health status and daily activities of COPD patients. This study investigated the relationship among daily physical activity (DPA), CAT scores, and bone mineral density (BMD) in COPD patients with or without OP. This study included 30 participants. Ambulatory DPA was measured using actigraphy and oxygen saturation by using a pulse oximeter. BMD was measured using dual-energy X-ray absorptiometry. OP was defined as a T-score (standard deviations from a young, sex-specific reference mean BMD) less than or equal to −2.5 SD for the lumbar spine, total hip, and femoral neck. We quantified oxygen desaturation during DPA by using a desaturation index and recorded all DPA, except during sleep. COPD patients with OP had lower DPA and higher CAT scores than those of patients without OP. DPA was significantly positively correlated with (lumbar spine, total hip, and femoral neck) BMD (r=0.399, 0.602, 0.438, respectively, all P<0.05) and T-score (r=0.471, 0.531, 0.459, respectively, all P<0.05), whereas CAT scores were significantly negatively correlated with (total hip and femoral neck) BMD (r=−0.412, −0.552, respectively, P<0.05) and (lumbar spine, total hip, and femoral neck) T-score (r=−0.389, −0.429, −0.543, respectively, P<0.05). Low femoral neck BMD in COPD patients was related to high CAT scores. Our results show no significant difference in desaturation index, low SpO₂, and inflammatory markers (IL-6, TNF-α, IL-8/CXCL8, CRP, and 8-isoprostane) between the two groups. Chest physicians should be aware that COPD patients with OP have low DPA and high CAT scores.

Keywords:

• chronic obstructive pulmonary disease
• osteoporosis
• daily physical activity
• COPD assessment test
• bone mineral density

Acknowledgments

The authors wish to thank the patients and personnel of the hospital unit for their cooperation during the course of this study. The study was supported by grants from the Chang Gung Memorial Hospital (CMRPG3B0011~3), Ministry of Science and Technology (MOST 103-2314-B-038-066-), and the Taipei Medical University (TMU102-AE1-B45).

Disclosure

The authors declare that they have not had any financial compensation and report no conflict of interest in this work.