Lymphocytosis linked to higher prevalence of hypothyroidism in patients with obstructive sleep apnea

The findings suggest that lymphocyte count can be used as an independent predictor of hypothyroidism occurrence and has diagnostic value for OSA combined with hypothyroidism.

Obstructive sleep apnea is a common sleep-breathing disorder. Several studies have revealed a strong inherent relationship between OSA and hypothyroidism. Studies indicate that lymphocytes may be involved in hypothyroidism development in OSA patients. Jing Zhang from the Department of Respiratory and Critical Care Medicine in Tianjin Medical University General Hospital, Tianjin, China, and colleagues aimed to assess the association between lymphocytes and hypothyroidism in OSA patients.

The study included 920 patients with obstructive sleep apnea who underwent nocturnal sleep monitoring, routine blood tests, and thyroid function testing. In OSA patients, logistic regression analysis indicated independent predictors of hypothyroidism.

The cutoff level of lymphocyte count was determined using a receiver operating characteristic (ROC) analysis to predict the occurrence of hypothyroidism in patients with OSA.

The study led to the following findings:

· The study comprised 920 OSA patients (617 males and 303 women), 879 with normal thyroid function, and 41 with hypothyroidism, with a hypothyroidism incidence of 4.46%.

· In the entire OSA population and male OSA patients, the number of lymphocytes was significantly higher in the hypothyroid group than in the control group.

· Among the OSA population younger than 60 years old and patients with mild to moderate OSA, lymphocytes were considerably more in the hypothyroid group than in the euthyroid group.

· Lymphocyte count, sex, and Epworth Sleepiness Scale (ESS) were all independent predictors of hypothyroidism development in OSA patients.

· According to ROC curve analysis, the risk of hypothyroidism increases with increasing lymphocyte count in the total patient population, with an optimal diagnostic cutoff point of 2.5 (× 10*9/L).

Based on the findings, lymphocyte levels tend to be higher in OSA patients who also have hypothyroidism, and this association is particularly significant in the overall OSA population and male patients.

Furthermore, the researchers discovered that lymphocyte count independently predicts hypothyroidism development in patients with OSA, which has not been previously reported.

"A simple blood test for lymphocyte count in OSA patients could indicate the occurrence of hypothyroidism in OSA patients, proving crucial in clinical practice," the researchers wrote.

Study limitations include a small sample size because of the exclusion of some patients with OSA, the lack of evaluation of continuous positive airway pressure or hormone supplementation on lymphocyte levels, and the lack of long-term follow-up.

Reference:

Fang, X., Wang, L., Xu, C. et al. The association of lymphocyte with hypothyroidism in obstructive sleep apnea. BMC Pulm Med 24, 60 (2024). https://doi.org/10.1186/s12890-024-02872-7