Association of nocturnal hypoxemia and white blood cell count in a multicenter cohort.

STUDY

OBJECTIVES

There is a higher risk of cardiovascular disease (CVD) in patients with obstructive sleep apnea (OSA) and innate immunity is a potential pathophysiologic pathway. The objective of this study was to determine whether nocturnal hypoxemia is associated with circulating markers of innate immunity in OSA.

METHODS

This was a cross-sectional study of an observational cohort from the multicentre, clinic-based, Canadian Sleep and Circadian Network. Oxygen desaturation index 4% (ODI4%) was used to diagnose and determine the severity of OSA. The percentage of time spent below SpO2 <90% (T90) and minimum SpO2 we considered as other measures of nocturnal hypoxemia. Multiple linear regressions were used to assess associations between total white blood cell (WBC) and subsets and ODI and hypoxemia indices.

RESULTS

A total of 1296 patients were included in the analysis. There was a positive association between ODI4% and lymphocyte count, adjusting for confounders. For every 1-SD increase in ODI4%, lymphocyte counts increased by 0.08 × 109 L (95% CI 0.01 to 0.15) SD. Patients with severe OSA (ODI4% ≥ 30 events/hour) had significantly higher total WBC and lymphocyte count than non-OSA cohort, in the adjusted model, p-value <.02, for both. There was a positive association between T90 and total WBC, neutrophil, lymphocyte, and monocyte count, adjusting for confounders. Minimum SpO2 was independently associated with total WBC, neutrophil, and monocyte counts.

CONCLUSIONS

In this pan-Canadian clinic-based cohort of individuals with suspected OSA, nocturnal hypoxemia indices were associated with an increase in total WBC and subset counts.