Prevalence and correlates of osteoporosis in chronic obstructive pulmonary disease patients in India

Abstract

Background: Chronic obstructive pulmonary disease (COPD) is a syndrome of progressive airflow limitation caused by the abnormal inflammatory reaction of the airway and lung parenchyma. Osteoporosis is one of the major extrapulmonary manifestations of COPD. The, prevalence of osteoporosis in COPD patients in Indian population is unknown.

Objectives: To study the prevalence of osteoporosis in COPD and to define various risk factors associated with reduced bone mineral density (BMD) in COPD.

Materials and methods: The study was done in the department of Pulmonary Medicine of a tertiary care hospital. All the diagnosed cases of COPD according to the Global Initiative for Obstructive Lung Disease (GOLD) guidelines were included in this study. The present study was a prospective study in for a period of 1 year. A brief history of the patients was taken, especially regarding duration of illness, number of exacerbations in the past 3 years, smoking in pack years, and history of steroid use (both systemic and inhaled steroids) after which cumulative dose of steroids was calculated. Spirometry was done in all these patients to stage the severity of COPD according to GOLD criteria. DEXA scan of the lumbar spine was done using bone densitometer to determine osteoporosis. A world Health Organization (WHO) criterion for definition of osteoporosis was applied and patients with T-score of > -2.5 standard deviation (SD) were diagnosed to have osteoporosis, -1 SD to -2.5 SD were diagnosed to have osteopenia and < -1 SD as normal. Statistical analysis for association of COPD with osteoporosis was done using chi-square test. Risk factors for osteoporosis were identified by univariate and multivariate logistic regression analysis.

Results: A total of 102 COPD patients were included in the study. Among these, 68 patients (66.6%) had osteoporosis and 20 patients (19.6%) had osteopenia. Majority (64.7%) of the patients who had osteoporosis had stage III and stage IV COPD disease. It was observed that as the severity grade of COPD increased, the risk of osteoporosis also increased. The bone mineral density (BMD) showed a significant difference among different stages of COPD. As the severity of the stage of COPD increased, BMD decreased. It was also observed that patients with lower body mass index (BMI) had higher prevalence of osteoporosis (37.3%) as compared to overweight patients. On univariate analysis, it was observed that risk factors for osteoporosis were female sex, higher number of exacerbations, BMI, and severity of COPD. After using multivariate logistic regression analysis, stage IV COPD (odds ratio (OR): 34.48, 95% confidence interval (CI): 1.59-1,000, P < 0.02), number of acute exacerbations >3 (OR: 30.3, 95% CI: 4.74-200, P < 0.01), and steroid cumulative dose >1,000 mg (OR: 7.35, 95% CI: 0.92-58.5, P < 0.04) were observed to be significant risk factors for osteoporosis in COPD patients.

Conclusions: In the present study, the prevalence of osteoporosis was 66.6% and another 19.6% had osteopenia. As the severity of COPD increased, the risk of osteoporosis increased. GOLD stage III and stage IV patient had significantly lower BMD as compared to stage I and stage II of COPD disease. Stage IV COPD disease, use of oral or parenteral glucocorticoids, and repeated number of exacerbations were found to be independent risk factors for osteoporosis in COPD patients. Thus, high clinical suspicion and early diagnosis and treatment is required in the evaluation of osteoporosis in COPD patients so that the quality of life can be improved in these patients.

Keywords: COPD; DEXA scan; correlates; osteoporosis; repeated exacerbations; risk factors.

Figure 1

Chronic obstructive pulmonary disease (COPD) related factors for osteoporosis and its functional consequences