Obstructive Sleep Apnea and Osteoporosis

Post on June 3, 2014 by André Broussard, D.C.

Obstructive Sleep Apnea and Osteoporosis: New Findings
—A large population-based cohort study in Taiwan demonstrates an elevated risk of osteoporosis in individuals with obstructive sleep apnea.

By Kevin O. Hwang, MD, MPH
Reviewed by Vrunda Bhavsar Desai, MD, FACOG, Assistant Professor of Obstetrics, Gynecology, and Reproductive Sciences, Yale University School of Medicine, New Haven, CT

While osteoporosis is generally considered a consequence of aging and changes in sex hormones, a number of chronic diseases are also implicated in the loss of bone mineral density. Hyperthyroidism, celiac disease, inflammatory bowel disease, and HIV are all known to increase the risk of osteoporosis.

This article will examine the risk of developing osteoporosis in patients with obstructive sleep apnea (OSA).
OSA is characterized by collapse of the upper airway during sleep, leading to abnormal gas exchange and recurrent arousals from sleep.

The prevalence of symptomatic OSA is estimated at 3% to 7% for adult men and 2% to 5% for adult women. There’s a growing body of literature examining the link between OSA and bone health. Small cross-sectional studies have produced conflicting results, however.

Yu-Li Chen and colleagues undertook a large population-based study to further characterize the relationship between OSA and osteoporosis.

 They conducted a retrospective analysis of data from Taiwan’s single-payer National Health Insurance program, which covers more than 98% of the country’s population. Data analysis was focused on a data subset including all insurance claims from 1996 to 2011 of 1 million beneficiaries who were selected in random fashion from the main dataset.

The study included an OSA group and comparison group recruited from 2000 to 2008. The OSA group had 1377 individuals over 40 years of age with OSA-related claims. The comparison group included 20,655 individuals (15:1 ratio) without OSA claims who were randomly selected from the dataset and matched by gender, age, and date of registration in the database. Patients were considered to have osteoporosis if they received dual energy X-ray absorptiometry before the diagnosis of osteoporosis, defined as T-score ≤2.5 standard deviations at any site. They were excluded if they had osteoporosis diagnosed before OSA.

Most patients (83%) in both groups were male, reflecting the greater prevalence of OSA among men. As expected, the OSA and non-OSA patients differed in important ways. The OSA patients were more likely than controls to live in a certain geographic region and have a higher income, as well as have hypertension, diabetes, hyperlipidemia, coronary artery disease, stroke, gout, chronic kidney disease, and obesity.

During the 6 years of follow-up, the incidence of osteoporosis in the OSA group was greater than that in the comparison group (2.52 versus 1.00 per 1000 person-years), with an incidence rate ratio (IRR) of 2.52 (95% confidence interval [CI] 1.59 to 3.99). The higher incidence of osteoporosis was evident in both men (IRR 2.87, 95% CI 1.41 to 5.86) and women (IRR 2.39, 95% CI 3.22 to 13.20). Patients with OSA were nearly 3 times more likely to develop osteoporosis in the analysis when adjusted for the demographic characteristics and comorbidities mentioned above (adjusted hazard ratio [HR] 2.74, 95% CI 1.69 to 4.44). Other than OSA, the only other factors related to an increased risk of osteoporosis in this cohort were older age and female gender. The authors noted that, “In our study, female patients had 8 times the risk for osteoporosis than the male patients had, suggesting that OSA may have more adverse effects on women than in men with regard to the development of osteoporosis. Further studies are needed to clarify this relationship.”

The study was limited by the lack of assessment of other risk factors for osteoporosis, such as family history, diet, physical activity, smoking, and medications.

 Another limitation was that the study didn’t evaluate how the OSA and comparison groups differed in bone mineral density measurements at specific bone regions (such as the hip or spine).
 It’s also unclear the extent to which individuals with OSA were treated with positive airway pressure or other interventions, and whether treated individuals had a lower risk of osteoporosis than untreated individuals.

The pathophysiology underlying the findings hasn’t been fully elucidated. It has been proposed that the hypoxia and inflammation associated with OSA adversely affect bone metabolism, increasing the risk for osteoporosis.

 It’s well known that hypoxia stimulates osteoclastic bone reabsorption. Patients with OSA also demonstrate higher levels of pro-inflammatory markers, which may act through a pathway involving the receptor activator of NF-kappaB ligand to increase bone destruction.

The Chen cohort study adds OSA to the long list of chronic medical conditions associated with osteoporosis. When considering which patients to screen for decreased bone mineral density, clinicians should be cognizant of the possible link between OSA and osteoporosis.

Published: June 03, 2014

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