Nighttime Oxygen Desaturation Found to Be Major Contributor to Daytime Sleepiness in OSA

In a new study, researchers compared the associations between several measures of breathing patterns during sleep and daytime sleepiness related to obstructive sleep apnea (OSA). They found that nighttime oxygen desaturation severity was a strong predictor of sleepiness.

Excessive daytime sleepiness (EDS) is a major symptom of OSA that can significantly diminish patients’ quality of life, including by impairing work performance. EDS can be measured by self-reported questionnaires and the objective Multiple Sleep Latency Test (MSLT), but prior research has found weak correlations between different measures of EDS and both apnea-hypopnea index (AHI) and oxygen desaturation index (ODI).

The investigators of this study set out to research how the severity of individual apneas (periods of no breathing), hypopneas (periods of slow/shallow breathing), and related oxygen desaturations are associated with mean daytime sleep latency (MSL), a measure of sleepiness. Specifically, they tested the ability of 2 novel diagnostic parameters, desaturation severity and obstruction severity, to predict daytime sleepiness compared with the predictive ability of AHI and ODI.

The study, published in the Journal of Clinical Sleep Medicine, used pairs of polysomnography (PSG) and MSLT recordings gathered at a hospital sleep disorder unit in Israel between 2001 and 2003. All patients had presented with complaints of sleepiness; they then underwent overnight PSG and a 4-nap MSLT the day after the PSG recording.

A multinomial analysis revealed that increased severity of sleep-related breathing cessations and accompanying oxygen desaturations had a stronger association with the severity of daytime sleepiness than did increases in AHI or ODI. For instance, a relative 10% increase in desaturation severity was associated with a risk ratio (RR) of 2.01 for experiencing severe daytime sleepiness (defined as MSL ≤5 minutes) and an RR of 1.30 for moderate daytime sleepiness (MSL >5-10 minutes) (both P <.05).

Because sex and desaturation severity were the most effective predictors of decreased MSL, they were the only variables retained for the general regression model, even though other parameters (eg, obstruction severity, AHI) were also significantly associated with daytime sleepiness. This model was used to calculate a graph of the inverse relationship between desaturation severity and MSL.

When assessing patients by sex, the correlations between each diagnostic parameter and MSL were not significant in women overall, but among only the women with severe OSA, the duration and severity of obstruction and desaturation were each associated with MSL, while AHI and ODI were not. Among men with severe OSA, desaturation severity had the strongest correlation with MSL (P = .03). In these men, desaturation severity explained 24.1% of the variance in MSL, whereas AHI and ODI accounted for 14.8% of the variance.

“We found that the novel parameters that quantify the severity of apneas, hypopneas, and desaturations had stronger correlation to MSL compared to AHI and ODI,” the study authors summarized. “Furthermore, increase in the values of novel parameters resulted in a higher risk of severe daytime sleepiness (MSL ≤5 minutes) compared to similar increase in the values of AHI or ODI.”

Based on these findings, the researchers suggested using desaturation severity and/or obstruction severity to diagnose OSA, which could help identify more patients with EDS and potentially avert some of the health consequences of OSA.

Reference

Kainulainen S, Töyräs J, Oksenberg A, et al. Severity of desaturations reflects OSA-related daytime sleepiness better than AHI. J Clin Sleep Med. 2019;15(8):1135-1142. doi: 10.5664/jcsm.7806.