State-dependent skin temperature increase during manic episodes of bipolar disorder

Abstract

Skin temperature changes during mood episodes and can be continuously monitored through wearable devices, potentially serving as a digital biomarker. We aimed to describe differences in skin temperature among bipolar disorder affective episodes and after symptomatic remission. We collected skin temperature through E4 wearable devices from a sample of 104 bipolar disorder patients in depressive, manic, or euthymic states, and 35 healthy controls. Participants in manic and depressive states were monitored for 48 h during acute episodes and after clinical remission, while euthymic patients and healthy controls were monitored just once. Data was analysed using generalized linear mixed models, considering group (depressive, manic, euthymic, or control) as the predictor of interest and season, movement, age, sex, and anticholinergic medication use as main potential confounders. Skin temperature was consistently higher in patients with manic episodes than in the rest of the groups during waking hours. Means from 9 am to 11 pm significantly differed between the manic group (33.61 °C) and the euthymic group (32.79 °C) (estimate = 0.82, IC 95 %: 0.02 to 1.62, p = 0.04). The increase in the group with mania dissipated after symptomatic remission (33.21 °C) (estimate = 0.41, IC 95 %: 0.32 to 0.49, p < 0.01). Lastly, the depression group showed no differences compared to other groups, nor between the acute state (32.98 °C) and remission (33.05 °C). Our results showed a state-dependent increase of skin temperature during waking hours in manic episodes, even after accounting for confounders, supporting its potential integration into multimodal monitoring frameworks.