Marino and co-workers developed methods to extract information from the EEG—a cybernetic signal emitted by the brain—that permitted objective characterization of each moment of human sleep. They used the methods to disambiguate the clinical stages of sleep, characterize sleep quality, identify REM sleep, classify subjects with mood disorders and obstructive sleep apnea, and to algorithmically stage sleep in a manner that complemented but did not mimic the traditional clinical method of sleep staging.

They presented evidence suggesting that a deficiency of Vitamin D contributed to poor quality sleep, excessive daytime sleepiness, and musculoskeletal pain, and they described a link between that obstructive sleep apnea and excessive daytime sleepiness.