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Investigation of the relationship between neutrophil-to-lymphocyte ratio and obstructive sleep apnoea syndrome

Published online by Cambridge University Press:  26 October 2015

S S Bakshi*
Affiliation:
Department of ENT and Head and Neck Surgery, Mahatma Gandhi Medical College and Research Institute, Pondicherry, India
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Abstract

Type
Letters to the Editors
Copyright
Copyright © JLO (1984) Limited 2015 

Dear Editors,

I came across a very interesting article published in your esteemed journal titled ‘Investigation of the relationship between neutrophil-to-lymphocyte ratio and obstructive sleep apnoea syndrome’ by Yenigun et al.Reference Yenigun and Karamanli1 The article is well written and I appreciate the effort put in by the authors. However, I am concerned about the authors’ conclusion and would like to express the same through your prestigious journal.

The increase in inflammatory markers and its effect on cardiovascular morbidity in obstructive sleep apnoeaReference Jiang, Cao, Wang, Liu, Cao and Chen2 has been known for quite some time. Neutrophil-to-lymphocyte ratio presents an exciting option for monitoring obstructive sleep apnoea patients because it is very simple to determine, and is not uncomfortable and cumbersome like polysomnography. However, a word of caution is advised, for multiple reasons.

Firstly, neutrophil-to-lymphocyte ratio varies with patient age and body mass index,Reference Li, Chen, Luo, Hong, Pan and Lin3 and will therefore vary from person to person. There are no standard cut-off values for neutrophil-to-lymphocyte ratio to determine whether it is abnormal or not. Without such standardisation, it is difficult to determine the significance of neutrophil-to-lymphocyte ratio in these patients.

Secondly, although abnormal neutrophil-to-lymphocyte ratio in obstructive sleep apnoea has been proven in previous studies,Reference Korkmaz, Korkmaz, Küçüker, Ayyıldız and Çankaya4 there are many other common conditions, such as Bell's palsyReference Kum, Yurtsever Kum, Ozcan, Yilmaz, Gungor and Unal5 and even chronic tonsillitis,Reference Yenigun6 where the values of neutrophil-to-lymphocyte ratio can be deranged. As the neutrophil-to-lymphocyte ratio can be influenced by so many common conditions, its specificity for use as a diagnostic tool comes into doubt.

Thirdly, although the authors have concluded that neutrophil-to-lymphocyte ratio correlates with the severity of obstructive sleep apnoea, it is not clear whether this relationship is linear or not. Only if the relationship is linear can it be used as a diagnostic tool for determining the severity of obstructive sleep apnoea. Another point which could have been evaluated is whether the neutrophil-to-lymphocyte ratio also depends on the duration of obstructive sleep apnoea and other co-morbid factors such as hypothyroidism. This can be done in future prospective trials.

I would like to conclude by stating that we still have a long way to go before we can truly analyse the significance of neutrophil-to-lymphocyte ratio in obstructive sleep apnoea.

References

1Yenigun, A, Karamanli, H. Investigation of the relationship between neutrophil-to-lymphocyte ratio and obstructive sleep apnoea syndrome. J Laryngol Otol 2015;3:16Google Scholar
2Jiang, H, Cao, H, Wang, P, Liu, W, Cao, F, Chen, J. Tumour necrosis factor-α/interleukin-10 ratio in patients with obstructive sleep apnoea hypopnoea syndrome. J Laryngol Otol 2015;129:73–8CrossRefGoogle ScholarPubMed
3Li, J, Chen, Q, Luo, X, Hong, J, Pan, K, Lin, X et al. Neutrophil-to-lymphocyte ratio positively correlates to age in healthy population. J Clin Lab Anal 2014. Epub 2014 Oct 2Google ScholarPubMed
4Korkmaz, M, Korkmaz, H, Küçüker, F, Ayyıldız, SN, Çankaya, S. Evaluation of the association of sleep apnea-related systemic inflammation with CRP, ESR, and neutrophil-to-lymphocyte ratio. Med Sci Monit 2015;21:477–81Google ScholarPubMed
5Kum, RO, Yurtsever Kum, N, Ozcan, M, Yilmaz, YF, Gungor, V, Unal, A et al. Elevated neutrophil-to-lymphocyte ratio in Bell's palsy and its correlation with facial nerve enhancement on MRI. Otolaryngol Head Neck Surg 2015;152:130–5CrossRefGoogle ScholarPubMed
6Yenigun, A. The efficacy of tonsillectomy in chronic tonsillitis patients as demonstrated by the neutrophil-to-lymphocyte ratio. J Laryngol Otol 2015;129:386–91CrossRefGoogle ScholarPubMed