The effect of mood phases on balance control in bipolar disorder.
The aim of this study was to investigate balance control during gait and sit-to-walk in individuals with bipolar disorder and healthy controls by examining the inclination angles between the whole-body center-of-mass (COM) and ankle in the sagittal plane. Twenty-one individuals with bipolar disorder in the euthymic (i.e., asymptomatic; n = 11) and depressed (n = 10) phases and 7 healthy controls (ages between 18 and 45) performed gait and sit-to-walk at self-selected comfortable speed. Mood phases for individuals with bipolar disorder were measured using the Patient Health Questionnaire and Altman Self-Rating Mania Scale. We collected motion data using a 16-camera motion capture technology. We found smaller COM-ankle inclination angles at seat-off during sit-to-walk for the bipolar-depressed group compared to the bipolar-euthymic and healthy groups, indicating poorly controlled balance for the bipolar-depressed group in sit-to-walk. However, we found larger COM-ankle inclination angles at beginning of single stance phase of gait for the bipolar-euthymic group compared to the healthy group, indicating well controlled balance for the bipolar-euthymic group in gait. Our results suggest an association between the depressed phase and balance impairment during daily movements in relatively young adults (ages ≤ 45 years). Our results also suggest that the depressed phase may be as detrimental to balance control as the effect of age-related neuromuscular weakness.