Increased sleep apnea-specific hypoxic burden is independently associated with cardiovascular autonomic dysfunction...

Sleep apnea-specific hypoxic burden (SASHB) is independently associated with cardiovascular disease (CVD) risk in patients with obstructive sleep apnea (OSA), and cardiac autonomic dysfunction (a well-established marker of CVD risk) is also linked to OSA. However, no previous studies have demonstrated an independent association between SASHB and cardiac autonomic dysfunction in patients with OSA.

A total of 2270 patients with suspected OSA were recruited between January 2021 and December 2024. We performed separate calculations for the SASHB and 19 heart rate variability (HRV) indices derived from time-domain, frequency-domain, and nonlinear method analyses. Correlations between variables were conducted using Spearman correlation analysis and Bonferroni correction for multiple comparisons. Multiple linear regression analysis was used to assess the independent association between SASHB and HRV indices. In addition, subgroup analyses were performed to explore differences in male and female subgroups.

After adjusting for multiple confounding variables, we found that with increasing SASHB values, the pNN50{Percentage of normal-normal (N-N) intervals differing by more than 50 ms} decreased from 18.77 to 15.04 (P < 0.001); SDANN (Standard deviation of the average NN intervals over all 5-min intervals) decreased from 60.93 to 57.19 (P < 0.001) and the Kurtosis of NN intervals decreased from 5.46 to 4.21 (P < 0.001). Conversely, the SDNN index (Standard deviation of NN intervals index) increased from 58.27 to 66.73 (P < 0.001); Ptot (Total Power) increased from 5830.85 to 6858.28 (P < 0.001); the Skewness of N-N intervals increased from -0.67 to -0.31 (P < 0.001); the alpha1 increased from 1.08 to 1.24 (P < 0.001), and the alpha2 increased from 1.04 to 1.07 (P < 0.001).

Our study was the first to confirm the independent association between SASHB and nocturnal cardiac autonomic dysfunction in patients with OSA, highlighting the need to monitor long-term nocturnal hypoxia in patients with OSA and coexisting cardiac autonomic dysfunction, preventing the occurrence of possible CVD risk.