Delta sleep-inducing peptide in normal humans and in patients with sleep apnea and narcolepsy

We measured morning plasma concentrations of delta sleep-inducing-peptide-like-immunoreactivity (DSIP-LI) in 9 sleep apnea patients, 10 narcolepsy patients, and 11 normal controls. Comparisons between the three groups showed no significant differences, although there was a trend toward association with low levels of DSIP-LI in the narcoleptic group, particularly in patients not using medications. No differences were found in the morning or evening plasma DSIP-LI levels in a second group of 11 normal controls and 8 sleep apneics. Our findings do not appear to support a biological marker role of disease activity for single measures of plasma DSIP in sleep apnea.