Dim Light Melatonin Onset (DLMO) – The Best Predictor of Sleep Timing

Due to the circadian system’s propensity to be modulated by important environmental cues including exposure to bright light, eating, social behavior, exercising and activity schedules, Dim Light Melatonin Onset (DLMO) patterns have been shown to reliably predict circadian timing and help clinicians more accurately assess sleep behavior and sleep phase shifts that can result in poor concentration, development, productivity, and diminished cognitive performance (Murray et al., 2017; Burgess et al., 2016; Burgess et al., 2015). Determining DLMO is also relevant in discriminating circadian rhythm related sleep issues from other non-circadian related sleep disorders or establishing the timing of exogenous melatonin administration when treating delayed sleep phase disorders (Lewy et al., 1995).

Interpreting Dim Light Melatonin Testing Results

The Phase Response Curve

Here is an example phase response curve showing data from a 7 sample circadian phase assessment. When applicable, DLMO is calculated using either the variable threshold 3k method (shown below), or the fixed threshold method to estimate the DLMO.

Clinicians and sleep experts routinely calculate DLMO using either the variable threshold method, aka “3k method”, or the fixed threshold method. The fixed threshold method is based on the time at which rising melatonin levels cross a previously determined threshold, typically set at 3 or 4 pg/mL for saliva. However, this method risks missing DLMO for individuals that are low melatonin producers, a common problem in an aging population. Salimetrics recommends using the 3k method to calculate DLMO (Voultsios et al., 1997, Molina and Burgess, 2011). This method establishes the mean of the first three low day-time samples and sets the threshold as 2 Standard Deviations above this mean for each person’s own measurements. The 3k method benefits DLMO determinations by including both individuals that are ‘low secretors’ who do not make sufficient melatonin to reach the fixed threshold values and allows for DLMO estimation in individuals who have daytime melatonin levels above the fixed threshold. In the case of 0 values, where melatonin production is below the reliable range of detection, the results report can still be calculated utilizing the threshold method.

A Comprehensive DLMO Interpretation

When sampled over time, a salivary Dim Light Melatonin Onset (DLMO) profile will enable the characterization of an individual’s circadian sleep physiology. The DLMO Results Report effectively provides baseline melatonin levels (while awake), melatonin onset (triggered by dim light exposure) and peak bedtime levels. Taken together these metrics compliment patient reported sleep behavior with sleep physiology. This information can lead to a more complete picture of causes of insomnia and/or circadian rhythm sleep disorders such as dysregulation and sleep phase shifts. Corrective actions to improve sleep quality may include strategically timed melatonin supplements, timed light exposure therapy sessions and/or specific improvements in sleep hygiene.

In general, a DLMO assessment will allow sleep-health providers to evaluate some key parameters:

Normal Sleep Onset
Typically, the melatonin onset should occur around two hours before bedtime, when melatonin levels have increased significantly enough to begin the sleep process. Some sleep disturbances are non-circadian sleep disorders and may not be directly tied to a sleep phase shift. A robust peak melatonin level and low baseline or waking level are both important aspects of a normal sleep onset. Normal Sleep Phase results need to be considered in the context of the patient’s overall presentation and available diagnostic data.

Phase Advanced
An advanced sleep phase, indicated by a DLMO that is earlier than ~2 hrs before habitual bedtime, is often seen in individuals who have difficulty staying awake until their desired bedtime in the evenings and often have problems staying asleep in the early morning hours. Often, therapy involving strategically timed exposure to blue light can inhibit melatonin production and delay the onset until the patient’s desired bedtime.

Phase Delayed
A delayed sleep phase, indicated by a DLMO that is later than ~2 hrs before habitual bedtime, is often seen in individuals who have problems falling asleep at their desired bedtime and difficulty waking up in the morning. Here, strategically timed treatment with proper melatonin supplementation can pinpoint the necessary increase in melatonin levels to help patients fall asleep at their desired bedtime.

No Onset / Undetermined
In profiles where the threshold is never crossed, such as flat-line results or atypically elevated thresholds, the interpretation of the DLMO cannot be calculated. This may indicate poor sleep hygiene or low levels of daytime light exposure. Atypically elevated thresholds can occur if one or more of the first 3 baseline values are abnormally elevated. Retesting is recommended for accurate results, ensuring careful adherence to test instructions.

Baseline Average
A high or elevated baseline indicates that melatonin levels were rising prior to the beginning of sampling. In this case, patients may have entered into a dim light area early or may be experiencing dysregulation from abnormal daytime levels of melatonin, often caused by supplementing higher doses than required. An interesting observation is the slow clearance of supplemental melatonin relative to endogenously produced melatonin. Supplements can cause high melatonin levels (above 40 pg/ml) for 24-48 hrs depending on the dose taken. These supplements can affect a person’s chronotype which has also been described as a melatonin hangover.

Peak Level
The peak level reported during the sampling regimen can be an important indication of sufficient melatonin production. A low peak level can indicate a suppressed melatonin onset and can result from inadequate daytime light exposure, cataracts, or poor sleep hygiene related to blue light exposure from screens or other sources. Children and adolescents should have very robust melatonin peak levels, in some cases well above 40 pg/ml. Melatonin peak levels decrease with age.