Obesity influences white matter integrity in schizophrenia

Abstract

Background: White matter (WM) alterations have been consistently described in patients with schizophrenia and correlated with the severity of psychotic symptoms and cognitive impairment. Obesity has been reported in over 40% of patients with schizophrenia and has been associated with cognitive deficits, cardiovascular diseases, metabolic alterations, and overall mortality. Moreover, studies among healthy subjects and subjects at risk for psychosis reported an influence of Body Mass Index (BMI) on structural connectivity. We therefore hypothesized that obesity and overweight could further disrupt WM integrity of patients affected by schizophrenia.

Methods: Eighty-eight schizophrenia patients were evaluated for BMI. We divided the sample in overweight/obese and normal weight groups. We then performed whole brain tract-based spatial statistics in the WM skeleton with threshold-free cluster enhancement of DTI measures of WM microstructure: axial (AD), radial (RD), and mean diffusivity (MD), and fractional anisotropy (FA).

Results: A significant difference between the two groups was observed: normal weight patients showed higher AD and a higher FA trend compared to obese patients in several fibers' tracts including longitudinal fasciculus, uncinate fasciculus, corona radiata, thalamic radiation, fronto-occipital fasciculus, cingulum and corpus callosum.

Conclusions: Elevated BMI might contribute to WM disruption of schizophrenia by hampering structural connectivity in critical cortico-limbic networks, known to play a crucial role in neurocognitive functioning, emotional processing and psychopathology whose dysfunction are prominent features of the disorder.

Keywords: Body mass index (BMI); Diffusion tensor imaging (DTI); Obesity; Schizophrenia; Tract-based spatial statistics (TBSS); White matter.