Longitudinal Stability and Contextual Sensitivity of At-Home Salivary Dim Light Melatonin Onset (DLMO): A Four-Year N-of-1 Study

The study tracked melatonin measurements in saliva (DLMO test) in a healthy adult male over four years with a total of 32 measurements. During 10 baseline measurements under standardized conditions, the timing of melatonin onset was highly stable (between 7:13 PM and 8:43 PM with a standard deviation of 28 minutes) and peak melatonin levels were consistent (average 13.26 pg/mL). Some factors such as magnesium, caffeine, alcohol, melatonin-rich foods, and intense exercise had no significant effect on melatonin timing. In contrast, bright light (~1500 lux) during the pre-onset period significantly suppressed melatonin production. Diazepam delayed melatonin onset and reduced its levels, while escitalopram increased baseline melatonin levels. A change in sleep time by 5 hours led to a corresponding delay in melatonin onset. The study demonstrates that various factors have different impacts on at-home DLMO test measurements.