The sema dreams are absolutely a widespread phenomenon even though they're not well-captured in the clinical trial data. They weren't a tracked adverse event in the STEP trials so we don't have great prevalence data, but patient forums and post-marketing surveys suggest it's common.
The proposed mechanisms:
- GLP-1 receptors in the brain: GLP-1R is expressed in the hypothalamus, brainstem, and — importantly — the hippocampus, which is involved in memory consolidation during sleep. Semaglutide crosses the blood-brain barrier. It may be modulating sleep architecture and REM cycles.[1]
- Blood sugar changes: More stable overnight glucose levels (especially in people with insulin resistance) can change sleep quality and dream recall. Hypoglycemia is known to increase REM sleep and vivid dreams.
- Weight loss itself: Significant weight loss improves sleep apnea, which increases time in REM sleep, which increases dream recall.
- Dietary changes: Eating less food, especially less food close to bedtime, can alter sleep architecture.
Most likely it's a combination of all of the above. The cat orchestra dreams are probably just your brain having fun with the extra REM time 😄
[1] Turton MD, O'Shea D, Gunn I, et al. "A role for glucagon-like peptide-1 in the central regulation of feeding." Nature. 1996;379(6560):69-72.