Association Between Red Cell Index and Depressive Symptoms in NHANES (2005-2018): A Cross-sectional Study.
Cheng Xing, Bowen Sui, Long He and 4 others
PMID 40179150WHAT IT FOUND
Among US cancer survivors, a blood index called RCI was not clearly linked to fewer depressive symptoms after accounting for demographics, blood tests, smoking and common illnesses.
A lower likelihood appeared only below a threshold value.
Key findings
01RCI per 1 unit was not associated with depressive symptoms after adjustment for smoking, hypertension and diabetes (OR 0.87, 95% CI 0.76-1.01, P = .063).
02Below RCI 1.265, each 0.1 unit increase was associated with lower odds of depressive symptoms (OR 0.916, 95% CI 0.847-0.991, P = .028).
03At or above RCI 1.265, RCI was not associated with depressive symptoms.
STILL TO COME
How it was doneWhat they foundWhat it means for RNs
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What it does not show
The study measured blood and depression scores at one time, so it cannot show whether RCI changes cause, result from, or simply travel with depression. Depression was measured by self-report on PHQ-9, so people may have misremembered or under-reported symptoms. Cancer status came from a questionnaire item about physician notification, not from medical records. Many NHANES participants were excluded for missing depression, blood index or covariate data, and the final analysis used 2890 cancer survivors. The authors note that RCI may be affected by primary tumours, so its reliability as a depression marker in cancer survivors is uncertain. The main fully adjusted continuous result was null, while the threshold finding was a secondary analysis in a narrow RCI range.
Declared interests
The paper reports funding from the Fifth Batch of National Outstanding Talents Training Project in Traditional Chinese Medicine. The supplied text does not list a commercial sponsor or author conflict of interest.
The easy way to misread this
Do not conclude that RCI can be used to screen depression risk in cancer survivors. The fully adjusted continuous association was not significant, and the cross-sectional design cannot show that RCI causes or predicts depression.