Abstract
Objectives: Evidence regarding the impacts of systemic inflammation on nocturnal sleep in advanced cancer patients is limited. We determined the association of serum C-reactive protein (CRP) levels with sleep in patients with non-imminent and those with imminent death. Methods: This was a secondary analysis of an observational study conducted in patients newly referred to a palliative care unit. Nocturnal sleep was assessed based on the "sleeping time" measured using a sheet-type non-wearable sensor. Patients were divided into long-survival and short-survival groups depending on the median survival (11 days), and within each group, the patients were categorized according to CRP levels: low (<1 mg/dL), moderate (1-10 mg/dL), and high (≥10 mg/dL). To evaluate correlations between CRP levels and sleeping time, binomial logistic analysis was performed. Adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were calculated. Results: A total of 535 patients were included in the main analysis. In the long-survival group (n = 273), the high-CRP patients had significantly longer sleeping time than the low-CRP patients (OR 2.81, 95% CI 1.19-6.65, p-value 0.019), whereas there were no significant correlations in the short-survival group (n = 262). Conclusions: Higher CRP levels were associated with longer sleeping time in patients with non-imminent death, whereas there were no correlations in patients whose death was imminent. The clinical implications of serum CRP levels appear to vary with life expectancy in terminally ill patients with cancer. Further research is necessary to verify the present findings.