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.