based on data from 88 individuals.
Patients with bipolar disorder demonstrate cognitive impairment and brain structure abnormalities, including global white matter loss, that have been associated with poor outcomes, but data on the stability or progression of neuroanatomical changes are limited, wrote Julian Macoveanu, PhD, of Copenhagen University Hospital, Denmark, and colleagues.
In a study published in The Journal of Affective Disorders, the researchers identified 97 adults aged 18 to 60 years with recently diagnosed bipolar disorder and matched them with 66 healthy controls. Participants were enrolled in the larger Bipolar Illness Onset (BIO) study. All participants underwent structural MRI and neuropsychological testing at baseline and were in full or partial remission based on total scores of 14 or less on the Hamilton Depression Rating Scale and the Young Mania Rating Scale. Approximately half of the participants (50 bipolar patients and 38 controls) participated in follow-up scans and testing after 6-27 months (mean 16 months), because of limited resources, according to the researchers.
The researchers compared changes in cortical gray matter volume and thickness, total cerebral white matter, hippocampal and amygdala volumes, estimated brain age, and cognitive functioning over time. In addition, they examined within-patient associations between baseline brain structure abnormalities and later mood episodes.
Overall, bipolar patients (BD) showed a significant decrease in total cerebral white matter from baseline, compared with healthy controls (HC) in mixed models (P = .006). “This effect was driven by BD patients showing a decrease in WM volume over time compared to HC who remained stable,” the researchers wrote, and the effect persisted in a post hoc analysis adjusting for subsyndromal symptoms and body mass index.
BD patients also had a larger amygdala volume at baseline and follow-up than HC, but no changes were noted between the groups. Changes in hippocampal volume also remained similar between the groups.
Analysis of cognitive data showed no significant differences in trajectories between BD patients and controls across cognitive domains or globally; although BD patients performed worse than controls at both time points.
BD patients in general experienced lower functioning and worse quality of life, compared with controls, but the trajectories of each group were similar for both functional and quality of life.
The researchers found no significant differences over time in total white matter, hippocampus, or amygdala volumes between BD patients who experienced at least one mood episode during the study period and those who remained in remission.
The findings were limited by several factors including the small sample size and limited generalizability of the findings because of the restriction to patients in full or partial remission, the researchers noted. Other limitations included the variation in follow-up time and the potential impact of psychotropic medication use.
However, the results were strengthened by the use of neuropsychiatric testing in addition to MRI to compare brain structure and cognitive function, the researchers said. The data suggest that both amygdala volume and cognitive impairment may be stable markers of BD soon after diagnosis, but that decreases in white matter may stem from disease progression.
The BIO study is funded by the Mental Health Services, Capital Region of Denmark, the Danish Council for Independent Research, Medical Sciences, Weimans Fund, Markedsmodningsfonden, Gangstedfonden, Læge Sofus Carl Emil og hustru Olga Boris Friis’ legat, Helsefonden, Innovation Fund Denmark, Copenhagen Center for Health Technology (CACHET), EU H2020 ITN, Augustinusfonden, and The Capital Region of Denmark. Macoveanu had no financial conflicts to disclose.