Colrain, I. M., Crowley, K. E., Nicholas, C. L., Padilla, M., & Baker, F. C. (2009). The impact of alcoholism on sleep evoked Δ frequency responses. Biological psychiatry, 66(2), 177-184.
K-complexes (KCs) are evoked δ frequency electroencephalogram (EEG) responses during sleep that occur when large numbers of healthy cortical cells burst fire in a synchronized manner. The KC amplitude and incidence are sensitive measures of normal healthy brain aging. Given the known neurodegenerative consequences of alcohol abuse it was hypothesized that alcoholism would be associated with further KC amplitude and incidence reductions.
Eighty-four subjects (42 alcoholics) screened for medical, psychiatric, and sleep problems participated. The protocol involved the presentation of auditory stimuli during stage 2 sleep throughout a night in the laboratory. The KCs were identified and averaged, to enable measurement of the P2, N550, and P900 peaks.
Compared with control subjects, alcoholic men and women had lower KC incidence (p < .001) and P2 (p < .001), N550 (p < .05), and P900 (p < .05) amplitudes. There was a significant diagnosis × site interaction (p < .001), indicating the group difference was largest at frontal sites. Longer sobriety correlated with increased N550 amplitude (p < .01).
The KC incidence and amplitude were negatively impacted in alcoholic men and women with exacerbation of the normal aging effects, particularly over frontal scalp regions. The observed relationship between improvements in KC measures and increased time of abstinence suggests that these measures might provide a useful marker of brain recovery with continued abstinence from alcohol.