Intermittent hypoxia and oxidative stress in patients with sleep apnea syndrome

Dear Editor,

This is a response to a published article on “The relationships between intermittent hypoxia and oxidative stress in patients with sleep apnea syndrome [1].” This study looks into the effect of continuous positive airway pressure (CPAP) therapy on oxidative stress in patients with severe sleep apnea syndrome (SAS). It uses reactive oxygen species metabolites (d-ROMs) and biological antioxidants (BAP) as surrogate markers of oxidative stress before and after CPAP therapy. While the study tackles an essential topic by evaluating an easily applicable method in clinical settings, some critical concerns must be considered, both in terms of content and methodology.

For starters, the study does not go into greater detail on potential confounding factors that may alter oxidative stress markers. For example, the sample size (42 patients) is limited, and it is unclear whether adjustments were done for variables such as age, comorbidities (e.g., diabetes, smoking), or medications, all of which might alter oxidative stress levels independently of SAS. Furthermore, the analysis assumes a direct relationship between SAS and oxidative stress, while the complexities of oxidative stress pathways are not fully understood. It would be useful to incorporate additional inflammatory markers or endothelial function indicators to assess the systemic effects of SAS and CPAP treatment.

Second, the approach of measuring oxidative stress using d-ROMs and BAP has drawbacks. While these are commonly used indicators, they only provide a snapshot of oxidative imbalance and do not accurately reflect tissue-specific oxidative damage or the complete spectrum of reactive oxygen species involved in SAS disease. The study could be enhanced by incorporating more complex approaches such as high-sensitivity C-reactive protein (hs-CRP) or advanced lipid peroxidation indicators (e.g., malondialdehyde), which could provide more precise insights into the mechanisms underlying oxidative stress in SAS patients.

For novelty and future prospects, the study may benefit from a more longitudinal design with numerous follow-up points after CPAP treatment, allowing for a better understanding of CPAP's temporal effects on oxidative stress. Furthermore, it would be useful to compare oxidative stress markers in patients with optimal CPAP adherence to those with poor compliance, as CPAP adherence is a significant component that may influence therapy outcomes. Furthermore, studying the effects of various CPAP pressure settings or alternative treatments such as bilevel positive airway pressure (BiPAP) on oxidative stress may provide therapeutically useful insights into customized therapy methods.

Finally, the study's emphasis on simple, easily measured indicators for therapeutic use is a significant advantage. Future research should seek to evaluate the use of d-ROMs and BAP against more known clinical outcomes, such as cardiovascular events or long-term survival rates. Furthermore, investigating the association between oxidative stress and specific cardiovascular disorders (e.g., hypertension, atherosclerosis) in SAS patients could shed light on the pathophysiology of SAS and its cardiovascular consequences.

Author contributions

HD 50% ideas, writing, analyzing, approval. VW 50% ideas, supervision, approval.

Declarations

Conflict of interest

Authors declare no conflict of interest.

AI declaration

The authors use AI for language editing and translation of the article.