Oxygen Resaturation Rate: A New Marker for Excessive Sleepiness?

In a study published in Sleep Medicine, researchers noted that common parameters like the apnea-hypopnea index have a limited correlation with excessive daytime sleepiness (EDS), and that oxygen desaturation parameters may be a better predictive variable. The authors theorized that oxygen saturation may represent increased cardiovascular fitness and thus show a protective effect against EDS.

According to the lead author of the study, Timothy P. Howarth, oxygen saturation parameters showed significant associations with objectively assessed daytime sleepiness in patients with suspected obstructive sleep apnea (OSA). The authors noted these associations were independent of desaturation parameters and concluded both markers could be used to assess EDS.

Oxygen Resaturation Rate Predicts EDS in OSA

The study reviewed 1629 patients referred for polysomnography and multiple sleep latency tests from 2001 to 2011. The criteria for EDS was a mean sleep latency (MSL) below 8 minutes.

The cohort was 75% male, 53% obese, and had a median age of 54 years. The average resaturation rate was 0.59% per second, and the average desaturation event nadir was 90.4%.

The median MSL was 9.6 minutes, and 606 patients met the threshold for EDS. Notably, authors found patients who were younger, female, and had larger desaturations showed significantly higher resaturation rates (P<.001).

After adjusting for age, sex, body mass index, and average desaturation depth, researchers found resaturation rate was associated with significantly increased risk of EDS (odds ratio [OR], 1.28; 95% CI, 1.07-1.53) and also showed a significantly negative correlation with MSL (z-score standardized beta, –1; 95% CI, –0.49 to –1.52).

The report noted the beta associated with resaturation rate was numerically larger compared with desaturation death, though not significant (difference, 0.36; 95% CI, –1.34 to 0.62; P=.470).

“Oxygen resaturation parameters show significant associations with objectively assessed EDS independent of desaturation parameters,” the authors wrote. “Thus, resaturation and desaturation parameters may reflect differing underlying mechanistic pathways, and both [could] be considered novel and appropriate markers for assessing sleep-disordered breathing and associated outcomes.”

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