Background: Obstructive sleep apnea (OSA) is related to multiple complications including insulin resistance (IR), endothelial dysfunction, and increased risk of cardiovascular disease (CVD). The apnea–hypopnea index (AHI) was widely used to measure OSA severity but poorly correlated with complications above. This study aimed to evaluate whether a new metric, the sleep breathing impairment index (SBII), was associated with cardiovascular risk in patients with OSA.
Methods: This study enrolled 140 consecutive male OSA patients without overt atherosclerotic CVD events, including coronary heart disease, stroke, peripheral vascular disease, or heart failure. Data on baseline medical history, anthropometric and polysomnographic parameters, fasting biochemical measurements and endothelial function tests, and common questionnaires were collected. The SBII was calculated by the product of the duration of each obstructive event and the associated desaturation area. The primary outcome was the moderate-to-high Framingham 10-year CVD risk.
Results: The median age of enrolled patients was 40 (35– 48) years. Eighty subjects had a moderate-to-high Framingham CVD risk. Patients with SBII in the third and fourth quartile had an increased proportion of moderate-to-high Framingham CVD risk with an adjusted OR 6.28 (95% CI 1.10– 36.04) and 11.78 (95% CI 1.25– 111.38). Significant association was not demonstrated in AHI and the Framingham CVD risk.
Conclusion: Higher SBII was associated with an increased 10-year CVD risk after adjusting for multiple potential confounding factors. Additional valuable information derived from polysomnography besides AHI deserves to be paid more attention.
Keywords: obstructive sleep apnea, sleep breathing impairment index, apnea-hypopnea index, Framingham cardiovascular risk