REM latency in depression: is there one best definition?

Area of Science:

• Neuroscience
• Psychiatry
• Sleep Medicine

Background:

• Rapid Eye Movement (REM) sleep latency is a key biomarker in sleep research.
• Varied definitions of REM latency exist, potentially impacting research findings.
• Understanding REM latency's diagnostic utility in depression is crucial.

Purpose of the Study:

• To evaluate the concurrent validity of various REM latency definitions.
• To assess the ability of different REM latency metrics to differentiate between primary depressives and healthy controls.
• To examine the relationship between REM latency, sleep onset, and depression severity.

Main Methods:

• Compared multiple REM latency definitions using polysomnography data.
• Analyzed the diagnostic accuracy (sensitivity and specificity) of each definition in distinguishing patient groups.
• Correlated REM latency measures with Hamilton Depression Rating Scale scores.

Main Results:

• Concurrent validity varied across REM latency definitions, with ranges of 62.5%-70.8% for outpatients and 64.6%-70.8% for inpatients.
• Less stringent sleep-onset criteria reduced specificity but did not significantly impact sensitivity.
• All tested REM latency definitions showed significant correlation with depression ratings (p < 0.01).
• Shorter REM latencies in depressed individuals were linked to later NREM sleep onset, not earlier REM onset.

Conclusions:

• No single REM latency definition demonstrated superior diagnostic accuracy over others.
• REM latency measurement in depression research should consider sleep-onset criteria carefully.
• Findings suggest a complex relationship between REM sleep, NREM sleep timing, and depressive states.