Processing speed in bipolar disorder and relationship to peripheral inflammation: A 4-year longitudinal study

Area of Science:

• Neuroscience
• Psychiatry
• Cognitive Science

Background:

• Bipolar disorder (BD) is frequently associated with cognitive impairments.
• These cognitive deficits, particularly in processing speed, may worsen with age.
• The role of peripheral inflammation in the longitudinal cognitive trajectory of BD is not well understood.

Purpose of the Study:

• To investigate longitudinal changes in processing speed in individuals with BD.
• To examine the influence of peripheral inflammation (IL-6, TNF-α, C-reactive protein) on these cognitive trajectories.
• To compare cognitive changes between BD patients and age-matched healthy controls (HC).

Main Methods:

• A multi-cohort burst longitudinal design was employed with 69 BD participants and 101 HC.
• Processing speed was assessed thrice annually using the Brief Assessment of Cognition in Schizophrenia (BACS) Symbol Coding task.
• Mixed-effects models analyzed cognitive changes in relation to baseline inflammation and age.

Main Results:

• The BD group demonstrated significantly slower processing speeds than the HC group across all time points.
• No significant differences were found in the rate of cognitive change between the BD and HC groups.
• Baseline peripheral inflammation did not significantly predict longitudinal cognitive change in the BD group, though interactions suggested potential age- and inflammation-dependent effects.

Conclusions:

• Individuals with BD exhibit slower processing speeds compared to HC, but not necessarily accelerated cognitive decline.
• Peripheral inflammation does not appear to be a strong predictor of cognitive change trajectories in BD.
• Further research is needed to elucidate the intricate interplay between inflammation and cognitive function in bipolar disorder.