The Interaction of Obesity and Nocturnal Hypoxemia on Cardiovascular Consequences in Adults with Suspected Obstructive Sleep Apnea. A Historical Observational Study.

RATIONALE: The interrelationships between obstructive sleep apnea (OSA) and obesity are complex and bidirectional; however, current evidence regarding their combined effect on cardiovascular risk is limited and conflicting. Animal studies suggest that obesity may exacerbate the cardiovascular consequences of intermittent hypoxemia.

OBJECTIVES

In this historical observational study, we investigated whether obesity increases the effect of nocturnal hypoxemia on the incidence of cardiovascular events in adults with suspected OSA.

METHODS

All adults with suspected OSA who underwent diagnostic polysomnography at a large academic hospital between 1994 and 2010 were linked to provincial health administrative data to determine a composite cardiovascular outcome (hospitalization due to heart failure, myocardial infarction, stroke, or revascularization procedures). Using a competing-risk model and controlling for confounders, hazards were compared between four groups: group 1 comprised obese patients (body mass index >30 kg/m2) with oxygen desaturation (>9 min of sleep spent with SaO2 <90%); group 2 comprised obese patients without desaturation; group 3 comprised nonobese patients with desaturation; and group 4 comprised nonobese patients without desaturation. Interaction was measured using the relative excess risk due to interaction.

MEASUREMENTS AND MAIN

RESULTS

A total of 10,149 participants were followed, with 17%, 25%, 8%, and 50% in groups 1-4, respectively. Over a median of 7.8 years, 896 (8.8%) first cardiovascular events occurred. Group 1 was associated with the highest hazard compared with the other groups, using group 4 as a reference (hazard ratio [HR] for group 1, 1.84; 95% confidence interval [CI], 1.46-2.32; HR for group 2, 1.59, 95% CI, 1.29-1.95; HR for group 3, 1.51; 95% CI, 1.15-1.98). The relative excess risk due to interaction was -0.25 (95% CI, -0.78 to 0.27), indicating no interaction.

CONCLUSIONS

In adults with suspected OSA, the highest cardiovascular risk was found in obese patients with nocturnal oxygen desaturation; however, the effect of these two factors together does not exceed the effect of each factor considered individually.