Lung Disease-Specific Risk Factors for Hip Fracture in Smokers

Several lung disease-related factors may help predict the risk for hip fracture in current and former smokers, according to study results published in the Journal of Bone and Mineral Research.

While previous studies have highlighted the significant morbidity and mortality associated with hip fractures in smokers with lung disease, limited data are available on the effect of lung-specific factors on the fracture risk. The aim of the current study was to explore the association between lung-specific factors with the risk for hip fracture in smokers.

The study cohort included 9187 (51.4% men, median age of 60 years) current and former smokers from the Genetic Epidemiology of chronic obstructive pulmonary disease longitudinal observational cohort study, who were followed for a median of >7 years.

A total of 361 incident hip fractures were reported during the follow-up.

Several traditional risk factors were significantly associated with incident hip fracture, including older age (odds ratio [OR], 1.03; 95% CI, 1.02-1.05 per year), female sex (OR, 1.23; 95% CI, 1.0-1.54), personal history of osteoporosis (OR, 2.18; 95% CI, 1.65-2.89), prior compression fracture (OR, 2.41; 95% CI, 1.68-3.45), prevalent self-reported hip fracture (OR, 6.11; 95% CI, 4.06-9.17), rheumatoid arthritis (OR, 1.99; 95% CI, 1.45-2.74), and diabetes (OR, 1.73; 95% CI, 1.32-2.25).

In addition, several lung disease-specific risk factors for hip fracture were identified, including postbronchodilator forced expiratory volume in 1 second percent predicted (OR, 0.95; 95% CI, 0.92-0.99 for each 10% increase), Global Initiative for Chronic Obstructive Lung Disease (GOLD) classification (OR, 1.09; 95% CI, 1.002-1.19 for each higher stage), and 6-minute walk distance (OR, 0.92; 95% CI, 0.90-0.95 for each 30-m increase).

Additional lung disease-specific risk factors for hip fracture included ≥5% emphysema (OR, 1.34; 95% CI, 1.06-1.69), modified Medical Research Council Questionnaire score (OR, 1.10; 95% CI, 1.03-1.19 for each higher unit score), body mass index, airflow obstruction, dyspnea, and exercise (BODE) index (OR, 1.07; 95% CI, 1.01-1.13 for each higher unit score); total exacerbations (OR, 1.13; 95% CI, 1.10-1.16 per exacerbation), and annual exacerbations (OR, 1.37; 95% CI, 1.21-1.55 per exacerbation).

When added to models including established fracture risk factors, the presence of emphysema on CT scan, 6-minute walk distance, and acute exacerbation frequency significantly improved risk discrimination.

The study had several limitations, including missing data on several important risk factors for fractures, such as corticosteroid use and falls; relatively few patients with severe obstructive lung disease, limiting the generalizability of the findings to patients with frequent exacerbations or severe lung disease; and focusing only on hip fracture, although vertebral fractures are likewise associated with significant morbidity.

“We have identified lung disease-specific risk factors that are easily assessed during a routine office visit and improve risk discrimination when added to traditional risk prediction models,” concluded the researchers.

Disclosure:  Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.

Reference

Bon J, Nouraie SM, Smith KJ, et al. Lung-specific risk factors associated with incident hip fracture in current and former smokers. J Bone Miner Res. Published online August 4, 2020. doi:10.1002/jbmr.4103