In individuals with chronic obstructive pulmonary disease (COPD), the presence of comorbidities is associated with increased mortality risk. We wanted to study the association between bone mineral density (BMD) and mortality among individuals with COPD in a population-based cohort study. Participants were recruited from the second (1995-1997) and third (2006-2008) surveys of the HUNT Study and followed until February 2019. Hip and forearm BMD were included as continuous T-scores or categorized according to WHO criteria (normal, osteopenia, and osteoporosis). Hazard ratios with 95% confidence intervals were estimated by multivariable Cox regression models. In total, 2076 and 3239 participants were identified as having COPD by FEV1/FVC below lower limit of normal (LLN) or <0.70, respectively, according to Global Lung Initiative (GLI) and Global Initiative for Chronic Obstructive Lung Disease (GOLD). The prevalence of osteoporosis was 15.7% vs. 16.6% in the GLI-COPD vs. GOLD-COPD cohorts. Mean follow-up was 12.7 and 11.9 years. Lower T-scores were associated with a 5% (95% confidence interval (CI) 1.01-1.09) increased mortality in the GLI-COPD and GOLD-COPD cohorts, respectively. However, the presence of osteoporosis (T < -2.5), compared to normal BMD, was not associated with mortality in neither GLI-COPD (HR 1.13, 95% CI 0.91-1.41) nor GOLD-COPD cohorts (HR 1.22, 95% CI 0.99-1.51). Thus, a small positive association was found between decreasing BMD T-score and mortality in both GLI-COPD and GOLD-COPD. However, osteoporosis as defined by WHO was not associated with mortality, probably due to loss of power upon categorization.
Keywords: COPD; cohort study; comorbidity; epidemiology; mortality; osteoporosis.