Wearable devices tracked bipolar patients continuously, revealing sleep stage variability as the most sensitive early warning sign for hypomanic episodes

 — Tiny, day‑to‑day changes in how people cycle through sleep stages were the earliest warning sign that a hypomanic episode was starting in patients with bipolar disorder, according to a new study that continuously tracked sleep and movement with wearable devices.

Researchers from the Centre for Addiction and Mental Health in Toronto and collaborators in Canada and Europe followed adults with bipolar disorder for more than a year. The goal was to spot the earliest indicators of mood elevation so clinicians and patients can act before symptoms spiral. 

The findings appear in the Journal of Affective Disorders and were published online Jan. 8, 2025. 

The team ran a prospective, observational, “contactless” study. Participants wore devices that logged daily activity and sleep around the clock and completed a weekly self‑rating of manic symptoms using the Altman Self‑Rating Mania Scale (ASRM). 

The Altman scale is a short, self-reported questionnaire designed to assess the presence and severity of manic symptoms. It consists of five items to evaluate changes in a person’s typical state in following areas: positive mood, self-confidence, sleep, speech patterns, and activity.

A hypomanic episode was defined as one or more weeks with consecutive scores of 10 or higher. The researchers then used a time‑frequency analysis method to test how well different wearable signals identified the onset of those episodes. 

Out of 164 people followed for a median of 495 days, 50 experienced at least one hypomanic episode during the study. 

The most sensitive early marker was “within‑night variability in sleep stages,” meaning how erratically a person moved among light, deep and REM sleep from one night to the next. 

That signal identified oncoming hypomania. Variability in daytime activity came next. The data gathered was able to pick up pattern changes before symptoms were obvious. 

An algorithm looked for brief, sharp “spikes” in the time‑frequency patterns of sleep and movement—changes too small to notice in a daily diary, but clear when measured continuously. Because the data were captured passively, patients didn’t have to remember to log symptoms each day. 

The authors cautioned that the sample was modest and that results need to be replicated and tested in real‑world decision tools. Still, the strengths were notable: dense, continuous data; more than a year of follow‑up per person; and a transparent method to translate raw wearable signals into clinically relevant alerts.

For patients and families, the work suggests a practical path: smarter use of devices many already wear. 

If future studies confirm these results, clinicians could receive automated flags when a patient’s nightly sleep becomes unusually erratic, prompting check‑ins or early treatment adjustments.

Source: Journal of Affective Disorders, online Jan. 8, 2025; in print April 1, 2025.

Note from a reader: I wore a sleep tracker during a year-long experience with hypomania. I wore an Oura Ring. I used it primarily to track my total time asleep and my sleep score. I didn’t really keep track of the different phases of my sleep. I tried really hard to get 8 hours of sleep, with the help of Ambien and 100-200mg of Trazodone to help me stay asleep. It sometimes worked, but not always. As my hypomania slowly grew into full-blown mania, I lost interest in wearing the ring, and my sleep time steadily declined. I can see how sleep was a contributing factor, or at least and early warning of problems to come.

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