Citation:
Hunasikatti M. Not so fast: do not ditch the data if you do not like them. J Clin Sleep Med. 2020;16(11):1985.
The commentary by Won,1 “When will we ditch the AHI?” on the article by Wang et al,2 “Oxygen desaturation rate as a novel intermittent hypoxemia parameter in severe obstructive sleep apnea is strongly associated with hypertension,” raises important issues. The commentary notes that in Wang et al,2 the oxygen desaturation rate (ODR) outperformed the AHI, the oxygen desaturation index, the percentage of total sleep time spent with oxygen saturation <90%, and the minimum and mean oxygen saturation level in predicting cardiovascular outcomes. The authors showed that ODR, as assessed by Δoxygen saturation/Δt, had the strongest association with both blood pressure (BP) and short-term BP variability. However, a ΔBP mm Hg of 15 ± 4.8 for the faster ODR group when compared with a ΔBP mm Hg of 11.6 ± 3.6 for the slower ODR group (difference of 3.4 mm Hg) is not enough to have significant cardiovascular outcomes in patients with OSA. This finding can be contrasted with that of Mancia,3 who reported that the diastolic BP values of 30.8 mm Hg and 31.69 mm Hg predicted cardiovascular deaths and all-cause deaths, respectively. Cardiovascular outcomes need to be prespecified in the study for a prediction claim. However, the Mancia study did show that ODR had the strongest association with both BP and short-term variability.3
If ODR is confirmed to predict cardiovascular outcomes, then it may be measuring a different phenotype of OSA. However, this consideration does not mean that we can ditch the AHI. Let us supplement the new indexes with AHI. Decades of clinical experience with AHI in OSA need not be discarded because of its inherent limitations. Apneas and hypopneas may measure different phenotypes of OSA. As Kapur states, “Single metric is not adequate” for defining and managing OSA.5 It should be acceptable to include other parameters such as the oxygen desaturation index, a total sleep time with oxygen saturation <90%, ODR, the apnea index, and the hypopnea index in the evaluation of OSA. Why do we need a single parameter to begin with? The control of hypertension is measured with various parameters: systolic BP, diastolic BP, mean BP, BP variability, and 24-hour mean ambulatory BP measurements, each with their own limitations.4 OSA is a chronic condition like hypertension. As Kapur and Donovan5 comment, combining these different parameters may be better than any single index to deliver precision medicine to patients.
DISCLOSURE STATEMENT
This letter reflects the views of the author and should not be construed to represent FDA’s views or policies.
REFERENCES
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