Is high-sensitive C-reactive protein a biomarker for functional somatic symptoms? A population-based study

Area of Science:

• Immunology
• Psychiatry
• Epidemiology

Background:

• Functional somatic symptoms (FSS) are medically unexplained symptoms.
• Immune system alterations, particularly low-grade inflammation, are hypothesized to contribute to FSS through sickness behavior.
• High-sensitivity C-reactive protein (hs-CRP) is a marker of innate immune system activation.

Purpose of the Study:

• To investigate the association between hs-CRP levels and the presence and number of FSS in a general population cohort.
• To determine if hs-CRP serves as a biomarker for FSS, both cross-sectionally and longitudinally.
• To explore potential associations between hs-CRP and specific clusters of FSS.

Main Methods:

• A population-based cohort of 881 adults was assessed for 43 FSS using the Composite International Diagnostic Interview.
• Innate immune function was measured via hs-CRP levels at baseline and approximately two years later.
• Regression analyses were performed, adjusting for relevant covariates including demographics, lifestyle factors, anxiety, and depression.

Main Results:

• No significant cross-sectional or longitudinal association was found between hs-CRP and the total number of FSS.
• hs-CRP was not associated with gastrointestinal FSS, but showed a trend towards association with general and musculoskeletal FSS clusters.
• Exploratory analyses indicated that pure musculoskeletal complaints were primarily associated with hs-CRP levels.

Conclusions:

• hs-CRP is not a reliable biomarker for the overall burden of FSS in the general population.
• The potential association between hs-CRP and specific FSS clusters, particularly musculoskeletal symptoms, warrants further investigation.
• The findings suggest that low-grade immune activation, as measured by hs-CRP, may not be a primary driver for the majority of functional somatic symptoms.