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 Sa_O2 <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.