Objective: The relation between depression and immune parameters has been inconsistent, with some studies reporting immunosuppression while others reporting excessive immune responses in depressed people. This topic has not been extensively studied in the elderly, nor have researchers attempted to examine this issue in a non-linear manner. The latter predicts that depression is associated with immune disregulation, including immune suppression and excessive immune activity. The present study examined the non-linear relation between depressive symptoms and initial white blood cell count (WBC) among hospitalized elderly people.
Design: Cross-sectional analysis within a longitudinal study.
Materials and Methods: 204 patients aged 65 and above (60.3% men) admitted to internal medicine at the Soroka University Medical Center were recruited for this study. Patients with cancer and patients who could not communicate or were unwilling to sign an informed consent were excluded. Depression was assessed using the total 30-item Geriatric Depression Scale (GDS) and after removing the “Withdrawal/ Apathy/ [Lack of] Vigor (GDS-WAV)” subscale, to create of scale suitable to elderly patients. WBC was been taken from medical records as well as demographic data, diagnoses and medications, and nutritional status. To analyze a non-linear relation, we trichotomized WBC levels into low (< 6,000), normal (> 6000 to < 10,000), high (> 10,000).
Results: The prevalence of depression (GDS > 10) was 26.5%, prevalence of depression “GDS without WAV” was 24%. GDS-WAV scores were significantly higher among patients with low and high WBC (p < .05). After adjustment for age, nutritional status and diagnoses of diabetes, arthritis, heart disease and infections, this non-linear relation remained significant (p =.007). Finally, 40.5%, 17.1% and 37% of patients with low, normal and high WBC, respectively, were categorically depressed (p < .003).
Conclusion: Our findings suggest that depressive symptoms are associated with immunological disregulation (suppression and excessive immune activity) among hospitalized elderly patients with an acute illness. Future studies need to identify which elements of the immune system are suppressed and excessively active among depressed elderly people and the health consequences of this disregulation.
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