Prevalence and correlates of low-grade systemic inflammation in adult psychiatric inpatients: An electronic health record-based study

Abstract

Low-grade inflammation is a risk factor for depression, psychosis and other major psychiatric disorders. It is associated with poor response to antidepressant and antipsychotics, and could potentially be a treatment target. However, there is limited data on the prevalence of low-grade inflammation in major psychiatric disorders, and on the characteristics of patients who show evidence of inflammation. We examined the prevalence of low-grade inflammation and associated socio-demographic and clinical factors in acute psychiatric inpatients. An anonymised search of the electronic patient records of Cambridgeshire and Peterborough NHS Foundation Trust was used to identify patients aged 18-65 years who were hospitalised between 2013 and 2016 (inclusive). We excluded patients on antibiotics or oral steroids, or with missing data. Inflammation was defined using serum C-reactive protein (>3 mg/L) or total white cell count (>9.4 × 10⁹/L) as measured within 14 days of admission. Out of all 599 admissions, the prevalence of inflammation (serum CRP >3 mg/L) in the ICD-10 diagnostic groups of psychotic disorders (F20-29), mood disorders (F30-39), neurotic disorders (F40-48) and personality disorders (F60-69) was 32%, 21%, 22% and 42%, respectively. In multivariable analyses, low-grade inflammation was associated with older age, black ethnicity, being single, self-harm, diagnoses of schizophrenia, bipolar disorder, current treatments with antidepressants, benzodiazepines, and with current treatment for medical comorbidities. A notable proportion of acutely unwell psychiatric patients from all ICD-10 major diagnostic groups show evidence of low-grade inflammation, suggesting inflammation may be relevant for all psychiatric disorders.

Keywords: CRP; Depression; Immunopsychiatry; Inflammation; Psychosis; White cell count.

Fig. 1

Prevalence of Inflammation (CRP >3 mg/L or WBC >9.4 × 10⁹/L) by Diagnosis. Legend: CRP: proportion of inflamed patients as measured by CRP >3mg/L; WBC: proportion of inflamed patients as measured by WBC >9.4 × 10⁹/L.

Fig. 2

Adjusted Odds Ratios for Inflammation (CRP >3 mg/L or WBC >9.4 × 10⁹/L) for Demographic and Clinical Factors. Legend: BAD: bipolar affective disorder; PD: personality disorder; SH: self-harm. NOTE: Reference categories are: female for sex, white for ethnicity, single for marital status, 18–27 for age, other for diagnosis, the absence of the condition for each comorbidity, and ≤13 days for length of stay. ORs are adjusted in a logistic regression model with inflammation (CRP >3 mg/L) as the dependent variable, and sex, age, marital status, ethnicity, main diagnosis, comorbidities, current medication, length of stay as predictor variables.