This will be a single-center, prospective observational study designed to evaluate the feasibility and accuracy of a new wearable device for non-invasive continuous monitoring of physiological signals to derive circadian rhythm. Melatonin sampling will be included for comparison against wearable-derived measures

Inclusion Criteria:

• Adults ≥18 years at screening.
• Able and willing to provide written informed consent.
• Belonging to one of three strata: (a) healthy controls without diagnosed sleep disorder, (b) patients with physician-diagnosed OSA, or (c) patients with physician-diagnosed insomnia (based on DSM-5/AASM criteria and ISI ≥15)
• Capable of using a smartphone for app-based data syncing.
• Willing to comply with study visits, wearable use, and saliva sampling.

Exclusion Criteria:

• • Dermatologic conditions preventing wearable use.

  • Significant psychiatric or neurologic illness that may impair compliance.
  • Shift work or trans-meridian travel within 2 weeks prior.
  • Currently pregnant
  • Use of medications known to significantly alter circadian rhythm (e.g., exogenous melatonin, beta-blockers).

Pilot study to determine feasibility only