Any clinical significance to very long sleep cycles? i have 4 hour rem latency and only 2-3 full cycles per night. confirmed by three separate psgs.

Not necessarily: Prolonged REM sleep latency can be due to any number of factors including medications (eg sertraline, fluoxetine), obstructive sleep apnea, etc. Be sure to practice sleep hygiene and confirm that you have refreshing sleep. See your neurologist or pulmonary sleep specialist for further discussion. http://www.nlm.nih.gov/medlineplus/sleepdisorders.html