Background: Abnormalities in psychomotor activity are a central and essential feature of affective disorder. Studies measuring differences in psychomotor activity between unipolar and bipolar disorder show divergent results and none have used a combined heart rate and movement monitor for measuring activity during free-living conditions.
Objective: To compare objectively measured psychomotor activity in patients with unipolar and bipolar disorder in a remitted or mild/moderate depressive state. Further, both groups were compared to a healthy control group.
Methods: A cross-sectional study of outpatients suffering from unipolar (n=20) and bipolar (n=18) disorder and healthy controls (n=31), aged 18-60 years. For three consecutive days a combined acceleration (m/s(2)) and heart rate (beats per minute) monitoring was used in conjunction with a step test to estimate activity energy expenditure (J/min/kg) as measures of psychomotor activity and physical fitness.
Results: Overall score on Hamilton-17 items ranged between 0 and 22. Patients had higher sleeping heart rate (p<0.001), lower fitness (p=0.02), lower acceleration (p=0.004), and lower activity energy expenditure (p=0.004) compared to controls. Comparing unipolar and bipolar patients and adjusting for differences in Hamilton-17 revealed lower acceleration (p=0.01) and activity energy expenditure in bipolar patients (p=0.02); the difference was most prominent in the morning.
Conclusions: Electronic monitoring of psychomotor activity may be a promising additional tool in the distinction between unipolar and bipolar affective disorder when patients present in a remitted or depressive state.
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